فهرست مطالب

آب و خاک - سال سی‌ام شماره 5 (آذر و دی 1395)
  • سال سی‌ام شماره 5 (آذر و دی 1395)
  • تاریخ انتشار: 1395/10/28
  • تعداد عناوین: 30
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  • علمی - پژوهشی
  • وحید رضاوردی نژاد، مریم شبانیان اصل، سینا بشارت صفحات 1334-1346
    در این مطالعه تبخیرتعرق روزانه گیاه مرجع، گوجه فرنگی و خیار گلخانه ای به روش لایسیمتری در منطقه ارومیه اندازه گیری شد. برای مدل-سازی تبخیرتعرق در گلخانه، انواع مدل های رگرسیون های خطی، غیرخطی و شبکه های عصبی مصنوعی در نظر گرفته شد. برای این منظور پارامترهای اقلیمی موثر بر فرایند تبخیرتعرق شامل دما (T)، رطوبت نسبی (RH)، فشار هوا (P)، کمبود فشار بخار اشباع (VPD)، تشعشع داخل گلخانه (SR)، تعداد روز پس از کشت (N) اندازه گیری و در نظر گرفته شدند. براساس نتایج، تابع نمایی سه متغیره از VPD، RH و SR با RMSE برابر 378/0 میلیمتر بر روز، دقیق ترین مدل رگرسیون در تخمین تبخیرتعرق مرجع به دست آمد. RMSE مدل بهینه شبکه عصبی مصنوعی در تخمین تبخیرتعرق مرجع برای داده های آزمایش و آزمون به ترتیب 089/0 و 364/0 میلیمتر بر روز به دست آمد. در تخمین تبخیرتعرق خیار، عملکرد مدل های لگاریتمی و نمایی به ویژه در تعداد متغیر مستقل زیاد، مناسب بود و دقیق ترین مدل رگرسیون مربوط به تابع نمایی با پنج متغیر N، VPD، T، RH و SR با RMSE برابر با 353/0 میلیمتر بر روز به دست آمد. همچنین در تخمین تبخیرتعرق گوجه فرنگی، دقیق ترین عملکرد مدلهای رگرسیون برای تابع نمایی چهار متغیره از N، VPD، RH و SR با RMSE برابر 329/0 میلی متر بر روز به دست آمد. بهترین عملکرد شبکه عصبی مصنوعی برای تخمین تبخیرتعرق هر دو محصول خیار و گوجه فرنگی، با پنج پارامتر ورودی VPD، T، N، RH و SR به دست آمد. مقادیر RMSE داده های آزمون تبخیرتعرق خیار و گوجه فرنگی به ترتیب 24/0 و 26/0 میلی متر بر روز به دست آمد که نشان دهنده ی عملکرد دقیق تر شبکه های عصبی در مقایسه با رگرسیون خطی و غیرخطی می باشد.
    کلیدواژگان: ارزیابی عملکرد، رگرسیون چندمتغیره، متغیرهای هواشناسی
  • مرتضی دلفان آذری، عاطفه پرورش ریزی صفحات 1347-1357
    در سامانه های آبیاری یکی از علل کاهش راندمان ایستگاه های پمپاژ، استفاده از روش های نامناسب تنظیم و کنترل جریان در زمان بهره برداری است. در این تحقیق پس از طراحی سامانه آبیاری قطره ای، منحنی مقاومت سامانه استخراج شد و پمپ ها دقیقا متناسب با نیاز سامانه انتخاب شدند. شیر کنترل دبی یک روش متداول کنترل جریان در لوله رانش پمپ های دور ثابت است. بنابراین با درنظر گرفتن سه روش مختلف کنترل دبی بوسیله شیرکنترل در پمپ های دور ثابت، و همچنین بهره برداری از ایستگاه مجهز به پمپ دور متغیر، مقدار مصرف انرژی در شیوه های مختلف بهره برداری مقایسه شدند. نتایج حاکیست که به شرط طراحی مناسب، بالاترین راندمان مصرف انرژی در استفاده از پمپ های دور متغیر است که تلفات انرژی را 44 تا 54 درصد کاهش می دهد.
    کلیدواژگان: پمپ دور متغیر، تلفات انرژی، سامانه های آبیاری، شیر کنترل دبی
  • سهیلا توفیقی، جمال محمد ولی سامانی، سیدعلی ایوب زاده صفحات 1358-1369
    در رسوبشویی تحت فشار مخلوط آب و رسوب توسط مجرای تخلیه کننده تحتانی از مخزن سد تخلیه می شود و حفرهای از آبشستگی به شکل مخروط جلوی تخلیه کننده بوجود آمده و توسعه می یابد. در تحقیق حاضر، تاثیر توسعه مجرای تخلیه کننده تحتانی در مخزن و تحلیل آماری آشفتگی نزدیک کف در این فرآیند مورد مطالعه قرار گرفته است. آزمایشات با عمق و دبی های مختلف جریان در طول های مختلف توسعه مجرا به منظور تعیین ژئومتری مخروط رسوبشویی طراحی و انجام گردید و برای بررسی پدیده های آشفتگی، برداشت سرعت جریان با استفاده از دستگاه سرعت سنج صوتی داپلر صورت گرفت. نتایج نشان دهنده تاثیر مثبت و محسوس توسعه مجرا در مخزن بر ابعاد مخروط رسوبشویی است، به طوریکه توسعه به میزان 5/0،1و 5/1 برابر ارتفاع رسوبات در مخزن موجب افزایش طول مخروط رسوبشویی به میزان 48، 83 ،113 درصد و افزایش حجم مخروط به میزان 50، 74 و 96 درصد نسبت به حالت بدون توسعه مجرا میگردد. بررسی پدیده های آشفتگی نزدیک کف نیز نشان داد که در درون مخروط رسوبشویی احتمال وقوع پدیده های جاروبی و بیرونرانی بیشتر از پدیده های اندرکنش روبه بیرون و رو به داخل هستند و زاویه اعمال نیروی لحظه ای ناشی از این پدیده ها بر کف مخروط رسوبشویی با کاهش فاصله از دهانه ورودی مجرای تخلیهکننده کاهش و قدرت جریان افزایش می یابد. همچنین با افزایش طول مجرای تخلیهکننده در مقاطع متناظر هم، احتمال وقوع پدیده های جاروبی و بیرونرانی افزایش و میزان زاویه اعمال نیروی متلاطم کاهش می یابد.
    کلیدواژگان: تحلیل کوادرانت، حفره آبشستگی، زاویه اعمال نیروی متلاطم، سرعت جریان
  • مسعود نادری، محمد شایان نژاد، سجاد حیدری، بیژن حقیقتی صفحات 1370-1381
    تحقیق حاضر به منظور بررسی تاثیر سطوح مختلف آب آبیاری بر خصوصیات کمی و کیفی سیب زمینی (رقم بورن) و تعیین عمق آب مصرفی بهینه در شهرکرد انجام شد. این آزمایش در قالب طرح بلوک های کامل تصادفی با 7 تیمار سطوح مختلف آب آبیاری در 3 تکرار انجام شد. سطوح مختلف آب آبیاری عبارت بودند از:40، 55، 70، 85، 100، 115و 130 درصد کمبود رطوبت خاک از حد FC. نتایج نشان داد، سطوح مختلف آب آبیاری بر میزان عملکرد تاثیر معنی داری دارد به طوری که با افزایش آب آبیاری مقدار عملکرد نیز افزایش یافت. کمترین و بیشترین عملکرد به ترتیب مربوط به سطوح آبیاری 40 و 130 درصد آبیاری کامل با مقادیر به ترتیب 2/13 و 2/45 تن در هکتار بود. سطوح مختلف آب آبیاری تاثیر معنی داری روی درصد نشاسته، درصد قند محلول، درصد ماده خشک، کارائی مصرف آب آبیاری و وزن غده های بازارپسند در یک بوته دارد، به طوری که با افزایش آن درصد قند محلول و وزن غده های بازارپسند افزایش و میزان نشاسته و درصد ماده خشک کاهش می یابد. همچنین سطوح مختلف آب آبیاری، تاثیر معنی داری روی درصد ازت و وزن غده های بذری در یک بوته نداشت. بیشترین در آمد به ازای عمق آب مصرفی 821 میلی متر (126 درصد آبیاری کامل) به دست آمد. در اثر کم آبیاری و استفاده از عمق بهینه ی، 533 میلی متر آب (82 درصد آبیاری کامل) می توان به حداکثر سود خالص نایل شد و با اعمال کم آبیاری می توان سطح زیر کشت را 22 درصد افزایش داد.
    کلیدواژگان: بهینه سازی، تابع تولید، تابع سود، کارائی مصرف آب آبیاری
  • مسلم اکبرزاده، بیژن قهرمان، کامران داوری صفحات 1382-1393
    در راستای پایش پایدار منابع آب، ارزیابی شبکه پایش و ارزیابی کیفیت آبخوان با تجزیه و تحلیل دقیق اطلاعات به دست آمده از مقادیر آلودگی حاصل می شود. از اساسی ترین این تحلیل ها سنجش دقیق پهنه های مستعد خطر و شناسایی ایستگاه های همگن از نظر شاخص آلودگی است. با شناسایی چاه های همگن از نظر آلودگی به نیترات می توان سبب بهبود شرایط پایش شد. براین اساس در این پژوهش، آبخوان شهر مشهد با دو معیار فاصله اقلیدسی و آنتروپی، خوشه بندی شد. نتایج نشان داد بهترین ساختار خوشه بندی با چهار خوشه همگن حاصل می شود. با توجه به پراکندگی چاه ها و میانگین گشتاورهای خطی، روش مبتنی بر معیار آنتروپی بر روش فاصله اقلیدسی برتری دارد. همچنین تغییرات نیترات نقش بسزایی را در شناسایی ایستگاه های همگن مبتنی بر آنتروپی ایفا می کند. بنابراین با خوشه بندی مبتنی بر آنتروپی می توان چاه های همگن از نظر تغییرپذیری شاخص آلودگی نیترات را شناسایی کرد که این امر می تواند گامی مهم و موثر در جهت پایش آبخوان مشهد و ارزیابی وضعیت کیفی آن باشد. همچنین در راستای ارزیابی و بهینه سازی شبکه پایش، هر چه شبکه موجود خوشه های کمتری به خود اختصاص دهد، همگنی بیشتری دارد. بنابراین رویکرد بهینه سازی از افزایشی به کاهشی (تعدیل شبکه پایش) توجیه خواهد داشت. در این صورت هزینه های پایش اعم از حفر، تجهیز، نمونه برداری، نگهداری و آنالیز آزمایشگاهی نیز کاهش می یابد.
    کلیدواژگان: آب زیرزمینی، آنتروپی، خوشه بندی، ضریب نیم رخ، فاصله اقلیدسی، کریجینگ فضایی زمانی، گشتاورهای خطی
  • زینب فتحی تیلکو، پرویز فتحی، فرزاد حسین پناهی صفحات 1394-1402
    بحران آب یکی از مسائل اساسی در مناطق خشک و نیمه خشک مانند ایران است. در این مناطق توجه به افزایش بهره وری آب در بخش کشاورزی ضرورتی اجتناب ناپذیر محسوب می شود. با استفاده از روش های نوین آبیاری نظیر آبیاری قطره ای نواری و نیز کاربرد استراتژی های آبیاری همچون کم آبیاری می توان بهره وری آب را افزایش داد. هدف از تحقیق حاضر بررسی تاثیر عمق جایگذاری نوار آبیاری قطره ای و سطح آب آبیاری بر عملکرد و بهره وری آب آبیاری محصول سیب زمینی (رقم آگریا) در دشت دهگلان، استان کردستان می باشد. آزمایش های مزرعه ای این تحقیق در قالب کرت های خرد شده بر پایه بلوک های کامل تصادفی و در سه تکرار انجام شد. کرت های اصلی و فرعی این طرح، به ترتیب، شامل سطح آب آبیاری ( 100،80،60و 120 درصد نیاز آبی گیاه ) و عمق جایگذاری نوار آبیاری قطره ای (0، 5، 10 و 15 سانتی متر) بود. نتایج نشان داد که اثر عمق آب آبیاری و عمق جایگذاری نوار آبیاری قطره ای بر عملکرد و بهره وری آب در سطح آماری یک درصد معنی دار می باشد. بیشترین عملکرد و بهره وری آب آبیاری به ترتیب مربوط به تیمارهای آبی 120 درصد و 60 درصد نیاز آبی گیاه می باشد. نتایج همچنین نشان داد که عمق جایگذاری نوار آبیاری برابر 15 سانتی متر، بهترین عمق جایگذاری نوار در شرایط استفاده از سیستم آبیاری قطره ای نواری در دشت دهگلان می باشد.
    کلیدواژگان: آبیاری میکرو، بحران آب، کارایی مصرف آب، کم آبیاری
  • رضا سجادی فر، جواد احدیان صفحات 1403-1414
    در این پژوهش ضریب انتشار آلاینده چگال، تحت جت هیدرولیکی در سیال پیرامون آب زلال و در حالت محیط پذیرنده ی کم عمق و عمیق به صورت آزمایشگاهی بررسی گردید. پارامترهای مورد بررسی شامل، دبی تزریق، غلظت سیال آلاینده، قطر و همچنین زاویه همگرایی نازل جت و محیط پذیرنده ی کم عمق و عمیق می باشد. آزمایش های این تحقیق در یک فلوم آزمایشگاهی برنامه ریزی و انجام گردید. نتایج آزمایش ها نشان داد، که ضریب انتشار تابعی از غلظت آلاینده و عمق محیط پذیرنده می باشد؛ به طوری که با افزایش غلظت، در محیط پذیرنده ی عمیق ضریب انتشار افزایش می یابد؛ از طرفی در محیط پذیرنده ی عمیق مشخص شد که افزایش عدد فرود چگال تا حدود 30 باعث کاهش ضریب انتشار می گردد و سپس ضریب به مقدار ثابت حدود 1/0 میل می نماید. همچنین نتایج نشان داد که در محیط پذیرنده ی کم عمق، مرزهای حرکتی به صورت غیرخطی با معادله ی درجه ی دوم توسعه می یابند. در این حالت حداکثر ضریب انتشار برابر با 28/0 و حداقل آن برابر با 095/0 بدست آمد. مقایسه نتایج در محیط کم عمق نشان داد که در یک عمق نسبی ثابت، با افزایش عدد فرود چگال از حدود 52 به 120 مقدار ضریب انتشار تا 7/2 برابر کاهش می یابد. این در حالی است که برای یک عدد فرود چگال ثابت، به طور متوسط با افزایش عمق نسبی از 5 به 15 مقدار ضریب انتشار در حدود 5/16 درصد افزایش می یابد.
    کلیدواژگان: آلاینده چگال، دبی جریان، عدد فرود
  • حمیدرضا مهرآبادی، احمد نظامی، محمد کافی، ملیحه احمدی فرد صفحات 1415-1425
    بررسی عکس العمل ارقام متحمل و حساس گیاه در شرایط تنش می تواند منجر به بهبود صفات مرتبط با تحمل و افزایش رشد و عملکرد گیاه پنبه در مناطق خشک شود. این پژوهش به منظور ارزیابی واکنش عملکرد چهار رقم حساس و متحمل به خشکی پنبه در سطوح مختلف آبیاری انجام گرفت. ارقام پنبه به عنوان کرت های فرعی در سه سطح آب آبیاری (به میزان 33، 66 و 100 نیاز آبی) به عنوان کرت های اصلی با استفاده از آزمایش کرت های خرد شده و در قالب بلوک های کامل تصادفی در سه تکرار در ایستگاه تحقیقات کشاورزی کاشمر طی سال 1390 مورد ارزیابی قرار گرفتند. نتایج نشان داد تمامی اجزاء عملکرد پنبه بجز وزن غوزه بطور معنی داری تحت تاثیر سطوح کم آبیاری قرار گرفتند. ریزش کمتر گل و غوزه و ابقاء بیشتر غوزه در بوته و حفظ زیست توده در شرایط تنش خشکی مهم ترین عوامل موثر در عملکرد ارقام متحمل به خشکی پنبه در مقایسه با ارقام حساس بودند. در شرایط تنش همبستگی بالا و معنی دار بین عملکرد وش با تعداد غوزه در بوته، عملکرد بیولوژیک و شاخص برداشت مشاهده شد. درصورتی که در شرایط آبیاری کامل این همبستگی تنها بین دو صفت ارتفاع بوته و عملکرد بیولوژیک دیده شد.
    کلیدواژگان: تنش خشکی، ضرایب همبستگی، شاخص برداشت، عملکرد، نیازآبی
  • آیدا مهر آذر، جابر سلطانی، امید رحمتی صفحات 1426-1439
    مدل‎های شبیه‎سازی، به دلیل ارائه تاثیرات کیفی وکمی آب بر عملکرد محصول، ابزاری ارزشمند برای بهبود مدیریت مصرف آب در مزرعه هستند.به همین منظور، در این طرح به ارزیابی مدل AquaCrop و بررسی دقت آن در شبیه‎سازیعملکرد محصول ذرت (Zea ma ys L) تحت تاثیر تنش شوری پرداخته شد. واسنجی مدل از طریق مقایسه‎ی نتایج حاصل از مطالعات صحرایی و نتایج شبیه‎سازی شده در مدل انجام شد. این آزمایش در قالب بلوک‎های کاملا تصادفی با پنج سطح شوری آب آبیاری شامل 0، 53/4، 06/9، 59/13 و 13/18 دسی زیمنس بر متر و چهار تکرار در دو زمان نمونه برداری در منطقه کرج اجرا شد. نتایج حاصل از مدل AquaCrop و مقایسه میانگین با روش چند دامنه ای دانکن و تجزیه واریانس داده ها در نرم‎افزار SAS ver 9.1 نشان داد که تنش شوری اثر بسیار معنی داری بر روی تمام صفات مورد اندازه‎گیری داشته به طوری که با افزایش تنش های شوری، کلیه صفات کاهش معنی داری پیدا کردند. نتایج شاخص‎های آماری نشان دادند که مدل AquaCrop در پیش‎بینی عملکرد ذرت تحت تاثیر تنش شوری دقت مناسبی دارد. طبق شاخص آماری CRM، مدل AquaCrop در پیش بینی عملکرد ذرت تحت تاثیر تنش شوری نسبت به عملکرد اندازه‎گیری شده در سطح مزرعه بیش‎برآورد داردو با افزایش میزان شوری خطای شبیه‎سازی عملکرد تحت تنش شوری بیشتر می‎شود. بیشترین و کمترین میزان خطا‎به ترتیب متعلق به تیمار 13/18 و 0دسی‎زیمنس بر متر می‎باشد و با گذشت زمان در برداشت دوم نیز همین روند ادامه یافته است.
    کلیدواژگان: تحلیل آماری، شوری آب، عملکرد محصول، مدل سازی، مدیریت مصرف آب
  • فرشاد فتحیان، احمد فاخری فرد، یعقوب دین پژوه، سید سعید موسوی ندوشنی صفحات 1440-1460
    مدل های سری زمانی از ابزارهای مهم در مدل سازی و پیش بینی فرآیندهای هیدرولوژیکی است که به منظور طراحی و مدیریت علمی پروژه های منابع آب به کار می روند. در این تحقیق به منظور مدل سازی میانگین دبی روزانه 6 ایستگاه آب سنجی واقع در بالادست سد زرینه رود از مدل های خطی خودهمبسته میانگین متحرک (ARMA) و غیرخطی خودهمبسته آستانه (TAR) 2 و 3 رژیمی استفاده شده است. به دلیل اینکه داده ها دارای نوسانات فصلی می باشند، در ابتدا داده های دبی روزانه برای یک دوره 15 ساله (2011-1997)، با استفاده از سری فوریه و برآورد شاخص های آماری نظیر میانگین و انحراف استاندارد، استاندارد شدند. سپس، داده های استاندارد شده برای یک دوره 13 ساله (2009-1997) واسنجی و یک دوره 2 ساله (2011-2010) صحت سنجی شدند. در نهایت، مدل های خطی و غیرخطی مناسب با استفاده از معیارهای آکائیکه و آزمون استقلال باقیمانده های مدل (Ljung-Box) انتخاب شدند. نتایج این تحقیق نشان داده است که بر اساس معیارهای ارزیابی، عملکرد مدل های غیرخطی آستانه 2 و 3 رژیمی برای همه ایستگاه ها دارای برتری نسبت به مدل خطی در مدل سازی جریان روزانه رودخانه های بالادست سد زرینه رود می باشد. همچنین مدل سازی و مقایسه مدل های غیرخطی آستانه نشان داد که مدل غیرخطی 3 رژیمی دارای معیارهای ارزیابی مناسب تری نسبت به مدل 2 رژیمی می باشد.
    کلیدواژگان: پیش بینی، دریاچه ارومیه، فرآیندهای هیدرولوژیکی، مدل های 2 و 3 رژیمی، معیارهای ارزیابی
  • عبدالرضا واعظی هیر، مهری تبرمایه صفحات 1461-1477
    محدوده مطالعاتی آلمانه با مساحت 7011 هکتار در جنوب غرب شهرستان مریوان واقع شده است. گسترش سازندهای ماسه سنگی و آذرین در این مناطق سفره های سازند سخت با منابع آبی مناسب از نظر کیفی بوجود آورده اند که در کنار منابع آبرفتی می توان از این آبخوان های سازند سخت برای تامین منابع آب استفاده نمود. بدین منظور در این پژوهش دو روش وزن دهی تجمعی ساده و فرآیند تحلیل سلسله مراتبی با بکارگیری فن بردار ویژه، برای پتانسیل یابی منابع آب زیرزمینی مورد استفاده قرار گرفته و پارامترهای مختلف به صورت لایه های لیتولوژی، تراکم شکستگی، ارتفاع، شیب، پوشش گیاهی و جهت شیب و تراکم آبراهه جهت بررسی پتانسیل منابع آبی در نظر گرفته شده است. در این راستا لایه های اطلاعاتی مربوط به هر کدام از این معیارها تهیه و در محیط GIS و IDRISI طبقه بندی، وزن دهی و با استفاده از وزن دهی تجمعی ساده و فرآیند تحلیل سلسله مراتبی تلفیق شدند. نتایج هر کدام از روش ها در پنج طبقه خیلی کم، کم، متوسط، زیاد، خیلی زیاد طبقه بندی شد. بر اساس نقشه های حاصل در هر دو روش مذکور به ترتیب مناطق شمالی غربی، غربی و جنوب غربی محدوده مطالعاتی دارای پتانسیل منابع آبی بیشتری نسبت به سایر مناطق بوده و دلیل آن می تواند انطباق این مناطق با مناطقی با شیب و ارتفاع پایین و پوشش گیاهی بالا و وجود پوششی از لایه تغذیه کننده آبرفتی سازند سخت باشد. مقایسه نتایج حاصل از دو روش با هم پوشانی موقعیت چشمه های موجود در منطقه و بررسی ارتباط بین تعداد چشمه ها و موقعیت قرار گیری آن ها بر روی مناطقی با آسیب پذیری متفاوت نشان می دهد که در محدوده مورد مطالعه روشAHP نسبت به SAW نتایج بهتری را نشان می دهد. بر اساس این روش بیش از 50 درصد منطقه دارای پتانسیل منابع آبی متوسط به بالایی می باشد که بیشتر مناطق غربی و مرکزی محدوده را شامل می شود.
    کلیدواژگان: آلمانه، پتانسیل یابی آب زیرزمینی، سازند سخت، فرآیند تحلیل سلسله مراتبی، وزن دهی تجمعی ساده
  • عبدالحسین ضیاییان، علیرضا فرحبخش، حسین بشارتی، لادن جوکار صفحات 1478-1488
    یکی از راه های موثر برای افزایش جذب فسفر در خاک های آهکی، استفاده از ریزجانداران خاکزی است. به منظور مطالعه نقش کاربرد باکتری های حل کننده فسفات و میکوریزا بر رشد و فراهمی فسفر سورگوم، آزمایشی گلدانی با 16 تیمار در سه تکرار، به صورت فاکتوریل در قالب طرح کاملا تصادفی اجرا گردید. تیمارهای آزمایشی ترکیبی از چهار سطح صفر، 25، 50 و 75 میلی گرم در کیلوگرم P2O5 از منبع سوپر فسفات تریپل، دو تیمار تلقیح و عدم تلقیح با باکتری حل کننده فسفات و دو تیمار تلقیح و عدم تلقیح با میکوریزا بود. نتایج نشان داد که با استفاده از باکتری حل کننده فسفات قطر ساقه، عملکرد ماده خشک، جذب فسفر و مقدار فسفر در خاک پس از برداشت افزایش معنی داری یافت. تلقیح قارچ میکوریز نیز تاثیر معنی داری
    کلیدواژگان: ریزجانداران خاک، خاک ها آهکی، کودهای زیستی، کودهای شیمیایی
  • علی افشاری، حسین خادمی، شمس الله ایوبی صفحات 1489-1501
    مطالعه حاضر با هدف بدست آوردن اطلاعاتی در مورد غلظت و الگوی شیمیایی برخی عناصر سنگین در خاک های اطراف زنجان تحت تاثیر کاربری های اراضی مختلف انجام گرفت. برای این منظور تعداد 241 نمونه خاک سطحی (عمق 10-0 سانتی متر) برداشت گردید که سهم کاربری-های اراضی کشاورزی، مرتع و شهری به ترتیب 137، 77 و 27 نمونه بود. غلظت کل (241=N)، قابل جذب (75=N) و عصاره گیری متوالی (75=N) به ترتیب با روش اسید نیتریک 5 نرمال، DTPA و تسیر انجام شده و با استفاده از دستگاه جذب اتمی قرائت گردید. نتایج نشان داد که غلظت کل سرب، روی، مس و کادمیم در کاربری شهری بالاتر می باشد (به ترتیب میانگین 1/220، 1/399، 9/75 و 47/2 میلی گرم برکیلوگرم). در کاربری شهری میانگین (هندسی) مقادیر قابل جذب عناصر نیز بالاتر از سایر کاربری های اراضی بود و برای روی، سرب، نیکل، مس و کبالت به ترتیب 09/27، 24/27، 11/1، 24/4 و 41/0 میلی گرم برکیلوگرم بدست آمد. کاربری اراضی مختلف تاثیر آشکاری بر توزیع فرم های شیمیایی عناصر گذاشته است. در تمام نمونه های خاک بیشترین درصد کبالت، نیکل و مس در جزء باقیمانده و کمترین مقدار برای کبالت جزء متصل به مواد آلی و برای نیکل و مس جزء تبادلی بود. جزءبندی روی و سرب در کاربری کشاورزی و مرتع تقریبا یکسان است و جزء باقیمانده بیشترین سهم را دارد. در کاربری شهری جزء متصل به اکسیدهای آهن و منگنز، جزء غالب بوده و برای روی و سرب به ترتیب 8/40 درصد و 8/30 درصد مشاهده گردید. جزء باقیمانده در این دو فلز در رتبه دوم قرار داشت.
    کلیدواژگان: آلودگی خاک، عصاره گیری متوالی، نوع استفاده از زمین، غلظت قابل جذب
  • سعید باقریفام، امیر لکزیان، امیر فتوت، رضا خراسانی صفحات 1502-1514
    در سال های اخیر آلودگی خاک ها و آب به آرسنیک به دلیل کاربردهای صنعتی و فعالیت های معدن کاری منجر به نگرانی های جدی زیست محیطی شده است. روش های مختلفی برای مدیریت زیست محیطی و پالایش خاک های آلوده پیشنهاد شده که در بین این روش ها گیاه پالایی به عنوان گزینه ای موثر و سازگار با محیط زیست مطرح شده است. به منظور پی بردن به اثرات همزیستی مایکوریزایی و غلظت فسفر بر جذب آرسنیت و آرسنات بوسیله گیاه آفتابگردان، مطالعه ای گلخانه ای به صورت کاملا تصادفی در قالب فاکتوریل با سه سطح مایکوریزا (شاهد، Glomus intraradices وmosseae Glomus)، دو سطح فسفر (0 و 60 میلیگرم بر کیلوگرم) و دو گونه معدنی آرسنیک (50 میلیگرم بر کیلوگرم آرسنیت یا آرسنات) انجام شد. نتایج حاصل از آزمایش نشان داد همزیستی مایکوریزایی غلظت آرسنیک در بخش هوایی گیاه را کاهش و افزایش سطح فسفر خاک غلظت آرسنیک را در بخش هوایی گیاه آفتابگردان افزایش می دهد. بنابراین همزیستی مایکوریزایی بوسیله گیاه آفتابگردان بازدهی تثبیت گیاهی و افزایش غلظت فسفر در خاک بازدهی جذب گیاهی آرسنیک را در خاک های آلوده به آرسنیک افزایش می دهد.
    کلیدواژگان: آرسنیت، آرسنات، تثبیت گیاهی، گیاه پالایی، مایکوریزا
  • امیر بیات، محمد هادی فرپور، اعظم جعفری صفحات 1515-1530
    تشکیل و تکامل خاک ها در مناطق خشک و نیمه خشک شدیدا تحت تاثیر سازندهای زمین شناسی و ژئومورفولوژی منطقه می باشد. نهشته های جوان کواترنری، مارن های نئوژن و کرتاسه از مهم ترین و گسترده ترین سازندهای زمین شناسی در منطقه بردسیر می باشند. هدف از این مطالعه بررسی تاثیر سازندهای زمین شناسی و همچنین اقلیم و سطوح ژئومورفولوژی بر ویژگی های فیزیکوشیمیایی، کانی-شناسی و میکرومورفولوژی خاک های منطقه می باشد. در این مطالعه 11 خاکرخ متاثر از این سازندها و در رژیم های رطوبتی اریدیک، مرز اریدیک- زریک و زریک و بر روی سطوح ژئومورفیک پدیمنت پوشیده و سنگی، دشت های سیلابی و دامنه ای، سطوح حدواسط، باهادا و تراس ها حفر شد. حداکثر مقدار گچ در خاک های واقع بر سازندهای کواترنری و مارن های کرتاسه و حداکثر مقدار کربنات کلسیم در سازندهای نئوژن مشاهده شد. خاک های متکامل مانند آلفی سول ها در رژیم رطوبتی زریک و سطوح ژئومورفولوژی دشت دامنه ای و خاک-های انتی سول در رژیم رطوبتی اریدیک و سطوح ژئومورفولوژی پدیمنت سنگی تشکیل شده اند. کانی های رسی مشاهده شده در این منطقه شامل اسمکتیت، ورمی کولیت، ایلیت، کائولینیت و کلریت می باشد که با حرکت از رژیم رطوبتی اریدیک به زریک نسبت اسمکتیت به ایلیت افزایش یافت. مطالعات میکرومورفولوژیکی نیز نشان داد با حرکت از رژیم رطوبتی اریدیک به زریک از بلورهای گچ کاسته شده و یا اثری از آن ها دیده نمی شود و بالعکس بر ضخامت پوشش های رس و بلورهای کلسیت افزوده شد. همچنین این مطالعات نشان داد عوارض خاک ساخت گچی عمده عوارض مشاهده شده در سازندهای کرتاسه و انواع عوارض خاک ساخت آهکی عمده عوارض مشاهده شده در سازندهای نئوژن می باشد.
    کلیدواژگان: آرجیلیک، ایران مرکزی، ردیف مواد مادری اقلیمی
  • مصطفی پژوهان نیا، مصطفی چرم، سیروس جعفری صفحات 1531-1542
    اشکال آهن و نسبت آن ها در خاک می تواند درجه تکاملی خاک ها را نشان دهد. هدف از این تحقیق، تعیین همبستگی بین شوری و سطح آب زیرسطحی بر تکامل خاک و اثرات زهکشی بر تشکیل این فرایندها در شرایط خاک های شور و غیرشور است. برای این منظور 12 خاک رخ و 6 مته در مناطق حاشیه جنوبی شوش و عبدالخان در استان خوزستان حفر گردید. خصوصیات فیزیکوشیمیایی خاک و اشکال آهن خاک به دو روش دیتیونایت سدیم (Fed) و اگزالات آمونیوم (Feo) عصاره گیری و اندازه گیری شد. نتایج نشان داد که نسبت آهن اگزالات به آهن دیتیونایتی در این خاک ها تحت تاثیر شوری، بافت خاک، مواد آلی،کشت وکار، سطح آب زیرسطحی متفاوت است. شوری برخی از خاکرخ ها سبب شده که ریزجانداران موثر بر فرایند اکسایش و احیا امکان فعالیت نداشته باشند. بین مقدار شوری آب و Fec و مقدار شوری آب وFeo همبستگی مثبتی ملاحظه شد ((R2=0.85. در مناطق شور، تجمع آهن بیشتر به صورت بی شکل و در منطقه غیرشور به شکل بلوری بود. این امر نشان دهنده شرایط مناسب برای تشکیل آهن بلوری در منطقه غیرشور است. با افزایش مقدار رس و قدمت کشت و کار، مقدار آهن بلوری هم بیشتر شد. نتایج نشان داد افزایش یون هایSO42- و –Cl در خاک ها، باعث واکنش این یون ها به آهن شده و مانع از تشکیل آهن بلوری می شود و آهن بیشتر به صورت بی شکل رسوب نموده است.
    کلیدواژگان: آب زیرسطحی، آهن بلوری، شوری و رنگدانه
  • فرناز ارشادفتح، حسین بانژاد، فریبا محسن زاده صفحات 1543-1555
    آفت کش ها در شمار مهم ترین آلاینده های آب های سطحی و زیرزمینی می باشند. تجزیه زیستی مهم ترین و موثرترین راه برای نابودی آفت-کش ها در محیط بشمار می رود. فنون زیست پالایی به دلیل هزینه های کم، سازگاری با محیط زیست و بازدهی زیاد به عنوان گزینه مناسبی جهت کاهش و یا حذف آلاینده ها از محیط مورد توجه می باشند. هدف از پژوهش حاضر بررسی پتانسیل حذف آفت کش کنفیدور از آب های آلوده توسط گونه های مختلف قارچ تریکودرما تحت تاثیر متغیرهای pH، غلظت سم و زمان می باشد. بدین منظور 3 گونه قارچ تریکودرما در pH های 5، 7 و 9 در محیط های کشت PDB حاوی غلظت های 1، 3 و 5 میلی گرم در لیتر از سم، کشت داده شدند. مقدار سم باقیمانده در نمونه ها در 4 مرحله قرائت و نتایج حاصل توسط نرم افزار SPSS تجزیه و تحلیل گردید. نتایج نشان داد گونه های قارچی مورد مطالعه قادر به حذف سم کنفیدور از آب آلوده می باشند و گونه T.harzianum با درصد حذف 34/60، از بیشترین توانایی و گونه T.tomentosum با راندمان حذف 60/44 درصد، از کمترین توانایی در زیست پالایش سم مذکور از آب های آلوده برخوردار می باشند. افزایش غلظت سم از 1 به 5 میلی گرم در لیتر، سبب افزایش درصد حذف سم کنفیدور از محیط های کشت گردید. نتایج درصد حذف سم کنفیدور در pH های مختلف نشان داد در همه گونه های قارچی راندمان حذف سم در 5= pHبالاتر از سایر pH ها می باشد.
    کلیدواژگان: ایمیداکلوپرید، پساب کشاورزی، زیست پالایی، قارچ
  • ولی فیضی اصل، امیر فتوت، علیرضا آستارایی، امیر لکزیان، میراحمد موسوی شلمانی، علی خراسانی صفحات 1556-1573
    نیتروژن مهمترین عامل تغذیه ای محدودکننده رشد گندم دیم بشمار می آید. به منظور برقراری ارتباط بین اشکال مختلف نیتروژن در خاک با پاسخ گندم دیم، پژوهشی در قالب طرح بلوک های کامل تصادفی به صورت کرت های دو بار خرد شده در ایستگاه تحقیقات کشاورزی دیم (مراغه) به اجرا در آمد. زمان مصرف نیتروژن در کرت های اصلی (کل نیتروژن در پائیز و در پائیز + در بهار)، مقادیر نیتروژن در کرت های فرعی (0، 30، 60 و 90 کیلوگرم در هکتار) و 7 ژنوتیپ در کرت های فرعی در 3 تکرار مورد بررسی قرار گرفتند. در مرحله ساقه رفتن (ZGS32)، نمونه های خاک از لایه های 20-0، 40-20، 60-40 و 80-60 سانتی متری از کرت های فرعی تهیه و نیترات و آمونیوم در آن ها اندازه گیری شد. در این لایه ها میزان رطوبت خاک نیز با استفاده از دستگاه Diviner2000 قرائت شد. نتایج نشان داد، نیتروژن معدنی مناسب ترین فرم نیتروژن بود که به همراه رطوبت خاک توانستند 80 درصد از تغییرات عملکرد دانه را توجیه نمایند. مطابق این مدل، اثر محتوی آب خاک در تولید گندم دیم، 3/2 برابر نیتروژن بود. مناسب ترین لایه برای واسنجی نیتروژن، 40-0 سانتی متری و حد بحرانی نیتروژن معدنی برای تولید عملکردهای بیش از 5/2 تن در هکتار، 41 کیلوگرم در هکتار می باشد. مصرف پائیزی 50 کیلوگرم نیتروژن در هکتار قادر به تامین حد بحرانی یادشده در شرایط آزمایش می باشد. در مجموع استنباط می شود، بین نیتروژن خاک و محتوی رطوبتی آن با پاسخ گندم دیم ارتباط منطقی وجود دارد و از این مدل می توان به عنوان ابزار کمکی در توصیه کودهای نیتروژنی برای گندم دیم استفاده نمود.
    کلیدواژگان: حد بحرانی، ژنوتیپ گندم، شبیه سازی، نیاز نیتروژن
  • وحید مرادی نسب، مهران شیروانی، شمس الله ایوبی، محمدرضا بابایی صفحات 1574-1583
    با توجه به کمبود آب در نواحی خشک و نیمه خشک کشور، استفاده از آب های نامتعارف نظیر فاضلاب های تصفیه شده جهت آبیاری گیاهان ضروری است. شرکت فولاد مبارکه جهت آبیاری قطره ای حدود 1350 هکتار از اراضی فضای سبز خود از فاضلاب صنعتی تصفیه شده این مجتمع استفاده می کند. لذا این مطالعه به منظور بررسی تاثیر آبیاری با پساب تصفیه شده این شرکت به مدت 2، 6 و 18 سال بر غلظت فلزات سنگین خاک در مقایسه با آب چاه و خاک بدون آبیاری انجام گرفت. بدین منظور از ناحیه پیاز رطوبتی درختان از سه عمق 20-0، 40 -20 و 60-40 سانتی متر نمونه های خاک تهیه و غلظت قابل دسترس و کل فلزات سنگین در آن ها اندازه گیری گردید. نتایج این مطالعه افزایش معنی داری را در غلظت آهن، مس، روی، سرب، کادمیم و نیکل قابل دسترس در خاک های آبیاری شده با پساب به مدت 6 و 18 سال نسبت به خاک بکر (نمونه شاهد) نشان داد. مقادیر کل فلزات سنگین نیز نسبت به نمونه شاهد افزایش یافت ولی غلظت این فلزات بطور قابل توجهی کمتر از استانداردهای سازمان محیط زیست کشور بود. بنابراین، استفاده از پساب حاصل از تصفیه فاضلاب صنعتی، حتی در درازمدت، سبب آلوده شدن خاک های اراضی فضای سبز شرکت فولاد مبارکه نشده است. بنابراین، آبیاری اراضی جنگلی با پساب تصفیه شده می تواند به عنوان روشی مناسب در مدیریت بحران آب در مراکز صنعتی کشور مورد استفاده قرار گیرد.
    کلیدواژگان: آب نامتعارف، آلودگی خاک، آبیاری قطره ای، پساب صنعتی
  • فرید فیض الله پور، مهدی کوچک زاده، فریبرز عباسی، محمدنبی غیبی، رجب چوگان صفحات 1584-1594
    کودآبیاری به دلیل امکان مصرف تقسیطی عناصر غذایی روشی موثر برای افزایش کار آیی مصرف آب و کود و کاهش تلفات کودهای نیتروژنی است .در پژوهش حاضر به منظور بررسی اثر مصرف تقسیطی کود اوره در کودآبیاری جویچه ای بر تلفات کود، تحقیقی بر روی ذرت دانه ای رقم سینگل کراس 260 در مزرعه پژوهشی موسسه تحقیقات اصلاح و تهیه نهال و بذر (کرج) در سال زراعی 1392 انجام شد. این آزمایش شامل 7 تیمار به صورت یک تیمار پخش سطحی کود و شش تیمار کودآبیاری بود و در چهار تکرار انجام گردید. طرح آزمایش به صورت فاکتوریل و در قالب طرح بلوک های کامل تصادفی اجرا گردید. فاکتور اول (S) شامل دو سطح تقسیط کود اوره (سه و چهار تقسیطی) و فاکتور دوم (N) شامل سه سطح کودی (100، 80 و 60 درصد توصیه کودی) بود. تیمارهای کودآبیاری در نهایت با روش کود دهی سطحی مورد مقایسه قرار گرفتند. کود مورد نیاز در تیمار سنتی در دو تقسیط مساوی و به صورت پخش سطحی به خاک اضافه گردید. بر اساس نتایج حاصل از تجزیه واریانس داده ها، درصد تلفات نیتروژن از طریق رواناب سطحی، تحت تاثیر مقدار کود مصرفی و اثر متقابل آن با تقسیط کود قرار گرفت. بیشترین تلفات نیتروژن توسط رواناب، در سطح کودی 100 درصد اتفاق افتاد و تفاوت معنی داری بین سطوح 60 و 80 درصد توصیه کودی حاصل نشد. از لحاظ درصد نیتروژن باقی مانده در خاک، تیمار سنتی با روش پخش سطحی کود، دارای بیش ترین مقدار نیتروژن موجود در خاک بعد از آزمایشات کودآبیاری بود. علاوه بر این در بررسی اثر متقابل تقسیط و مقدار کود مصرفی مشاهده شد که با کاربرد تنها 60 درصد توصیه کودی طی چهار تقسیط مساوی در طول فصل رشد، می توان ضمن دست یابی به عملکرد مطلوب، میزان آلودگی زیست محیطی را کاهش داد.
    کلیدواژگان: پخش سطحی، ذرت، رواناب، کارآیی مصرف کود
  • علیرضا کیانی، افشین مساوات صفحات 1595-1606
    تاثیر روش های مختلف آبیاری یکدرمیان با آب شور بر روی عملکرد ذرت، توزیع شوری و رطوبت در نیمرخ خاک در قالب طرح بلوک های کامل تصادفی با سه تکرار به مدت دو سال مورد بررسی قرار گرفت. تیمارهای آزمایشی شامل: T1 و T2 به ترتیب 100 و 50 درصد آب مورد نیاز گیاه با آب غیرشور، T3 و T4 آبیاری با آب غیر شور– شور به ترتیب بصورت متناوب و ثابت، T5 و T6 کم آبیاری با آب غیرشور و آبیاری یک درمیان به ترتیب بصورت ثابت و متناوب و T7 آبیاری کامل با آب شور بود. شوری آب آبیاری در تیمارهای غیرشور و شور به ترتیب 5/1 و 8 دسی زیمنس بر متر بود. تیمارهای کم آبیاری (T2، T5 و T6) و همچنین تیمارهای آبیاری با آب شور یک درمیان (T3 و T4) از نظر عملکرد نسبت به هم اختلاف معنی داری نداشته بطوری که عملکرد در تیمارهای T3 و T4 با 50 درصد ذخیره آب شیرین نسبت به تیمار T1 به ترتیب در حدود 7 و 1 درصد کاهش داشت. مقایسه توزیع رطوبت در تیمارهای کم آبیاری نشان داد که بیشترین رطوبت در سطح و عمق خاک به ترتیب مربوط به تیمارهای T6 و T2 بود. بررسی دو ساله ی توزیع شوری در نیمرخ خاک در تیمارهای T3 و T4 نشان داد که امکان کاربرد آب شور برای تولید ذرت وجود دارد ولی برای حفظ پایداری، زهکشی و آبشویی خاک مورد نیاز است.
    کلیدواژگان: آبیاری قطره ای، شوری، کم آبیاری
  • لیلا زارع، عبدالمجید رونقی، سیدعلی اکبر موسوی، رضا قاسمی صفحات 1607-1619
    به منظور مطالعه اثر کاربرد ورمی کمپوست بر رشد و ترکیب شیمیایی ذرت تحت تنش آبی، آزمایشی گلخانه ای به صورت فاکتوریل (3×4) و در قالب طرح کاملا تصادفی با سه تکرار اجرا شد. تیمارهای مورد استفاده شامل چهار سطح ورمی کمپوست دامی (0، 10، 20 و 30 گرم در کیلوگرم خاک) و سه سطح رطوبت ( 100، 80 و 60 درصد ظرفیت مزرعه) بود. نتایج نشان داد که افزایش سطوح ورمی کمپوست سبب افزایش معنادار وزن خشک ذرت و غلظت نیتروژن، فسفر، آهن، مس و روی در اندام هوایی ذرت شد. اما غلظت منگنز به طور معناداری کاهش یافت، هرچند غلظت منگنز در گستره کفایت بود. با افزایش سطوح تنش آبی وزن خشک ذرت به طور معناداری کاهش یافت و به دلیل کاهش زیست توده گیاه، غلظت عناصر ذکر شده در اندام هوایی ذرت افزایش معنادار داشت. کاربرد 30 گرم ورمی کمپوست تحت تنش آبی 60 و 80 درصد ظرفیت مزرعه، غلظت نیتروژن، فسفر، روی، مس و آهن اندام هوایی ذرت را نسبت به تیمار شاهد در هر سطح تنش آبی به طور معناداری افزایش داد. در سطح تنش آبی 60 درصد ظرفیت مزرعه کاربرد 30 گرم ورمی کمپوست سبب افزایش معنادار وزن خشک ذرت نسبت به تیمار شاهد (در تنش آبی مربوطه) شد. با توجه به اثر مثبت کاربرد ورمی کمپوست در کاهش اثر سوء تنش آبی بر عملکرد و غلظت عناصر غذایی و همچنین با توجه به نقش این کود در بهبود وضعیت تغذیه ای ذرت، کاربرد ورمی کمپوست می تواند کود مناسبی برای استفاده در زمین های کشاورزی که با مشکل کمبود آب مواجه هستند، باشد.
    کلیدواژگان: آهن، روی، مس و منگنز
  • محدثه سواسری، سید مصطفی عمادی، محمدعلی بهمنیار، پوریا بی پروا صفحات 1620-1633
    آلودگی خاک ها با فلزات سنگین یکی از مشکلات زیست محیطی عمده در جوامع بشری است. در این راستا استفاده از نانو ذرات آهن صفرظرفیتی به عنوان اصلاح کننده آلودگی های محیط زیست مورد توجه محققان می باشد. بدین منظور سنتز و تعیین مشخصات نانو آهن صفرظرفیتی پایدار شده با اسیدآسکوربیک (AAS – ZVIN) در شرایط هوازی و ارزیابی تاثیر آن بر قابلیت جذب کادمیوم در خاک و توزیع شکل-های شیمیایی آن در سه خاک شنی، اسیدی و آهکی مورد بررسی قرار گرفت. بدین منظور، آزمایش فاکتوریل در قالب طرح کاملا تصادفی با تیمارهایی شامل کادمیوم در سطوح 15 و 45 میلی گرم بر کیلوگرم و AAS – ZVIN در سطوح 0، 5/0، 1 و 2 درصد وزنی در سه خاک شنی، اسیدی و آهکی در دو دوره زمانی یک و چهار هفته با سه تکرار انجام شد. توزیع شکل های شیمیایی کادمیوم با استفاده از عصاره گیری دنباله ای تعیین گردید. نتایج تصاویر SEM، XRD نشان داد که نانو آهن سنتز شده با اسیدآسکوربیک به ترتیب دارای اندازه کمتر از 50 نانومتر، حداکثر پیک در2θ برابر 8/44 درجه دارد. نتایج نشان داد که در هر سه خاک شنی، اسیدی و آهکی، کاربرد 5/0، 1 و 2 درصد وزنی از AAS - ZVIN در هر دو سطح آلودگی 15 و 45 میلی گرم بر کیلوگرم مقدار کادمیوم قابل جذب کاهش یافت. با گذشت زمان از یک به چهار هفته با کاربرد AAS – ZVIN تغییرات کادمیوم قابل جذب، روند کاهشی داشت. هم چنین نتایج حاصل از عصاره گیری دنباله ای نشان داد که در هر سه خاک شنی، اسیدی و آهکی با افزایش غلظت AAS – ZVIN از صفر به 2 درصد وزنی، شکل های محلول و تبادلی و کربناتی کاهش و شکل های متصل به ماده آلی و اکسید آهن و منگنز و باقیمانده کادمیوم افزایش یافت. بنابراین می توان بیان داشت کارایی نانو آهن صفرظرفیتی در کاهش کادمیوم از خاک بالا بوده و می تواند به عنوان یک روش کارآمد در رفع آلودگی این قبیل خاک ها معرفی شود.
    کلیدواژگان: آلودگی خاک، عصاره گیری دنباله ای، قابل جذب با DTPA
  • مینا کیانی، محمدحسن صالحی، جهانگرد محمدی، عبدالرحمان محمدخانی صفحات 1634-1645
    آگاهی از نحوه ی تغییرپذیری مکانی ویژگی های خاک و ارتباط آن ها با عملکرد محصول در باغات برای دست یابی به تولید بیش تر و مدیریت بهتر ضروری می باشد. به منظور بررسی ارتباط آماری و زمین آماری برخی از ویژگی های فیزیکی و شیمیایی خاک با عملکرد، ویژگی های کیفی و رویشی پرتقال والنسیا در باغی به مساحت حدود 1 هکتار در منطقه کازرون استان فارس از دو عمق 40-0 و 80-40 سانتی متری، در مجموع، 120 نمونه خاک برداشت شد. نمونه برداری از درختان پرتقال بصورت ترکیبی از دو درختی که فاصله کمتری با نمونه های خاک داشتند، انجام گردید. ویژگی های فیزیکی و شیمیایی خاک، عملکرد، ویژگی های کیفی و رویشی پرتقال بر اساس روش های استاندارد تعیین شدند. نتایج آماری نشان داد که pH کم ترین (48/2درصد) و ویتامین ث پرتقال بیش ترین (46/59درصد) ضریب تغییرات را دارند. عملکرد پرتقال با ماده ی آلی و منگنز قابل جذب در عمق صفر تا 40 سانتی متری از سطح خاک، دارای رابطه ی مثبت و معنی داری (به ترتیب، 29/0 در سطح 95درصد و 31/0 در سطح 99درصد) بود. نقشه های حاصل از میان یابی توسط کریجینگ نشان داد ویژگی های خاک و عملکرد محصول دارای پراکنش مکانی هستند و همچنین، برخی از ویژگی های خاکی شامل درصد ماده آلی، پتاسیم محلول، فسفر، روی و منگنز قابل جذب در هر دو عمق نمونه برداری در شرق و جنوب شرقی منطقه ی مورد مطالعه بیش تر از دیگر مناطق می باشد که این نقشه ها با عملکرد میوه، الگوی پراکنش مکانی تقریبا مشابهی دارند. با توجه به تاثیری که عناصر و ماده آلی در این تحقیق نشان دادند مطالعه ی تاثیر مصرف کودها بر ویژگی های کمی، کیفی و رویشی پرتقال در باغات منطقه به منظور روشن تر شدن تاثیر این عناصر توصیه می گردد.
    کلیدواژگان: پراکنش مکانی، تغییر پذیری خاک، عملکرد و کیفیت پرتقال
  • ستاره شریفی، امیر لکزیان، علیرضا آستارایی، نسرین قربانزاده صفحات 1646-1661
    چرخه آهن یکی از مهم ترین فرآیندهای ژئوشیمیایی است که افزایش زیست فراهمی این عنصر در خاک ها وابسته به فرآیند کاهش زیستی آهن فریک است. در این پژوهش اثر سه ناقل الکترون AQS، اسیدهیومیک و اسیدفولویک در فرآیند کاهش زیستی آهن فریک با دو باکتری در دو خاک اسیدی و آهکی در شرایط بی هوازی آزمایشگاهیبررسی شد. آزمایش در قالب فاکتوریل با طرح کاملا تصادفی با سه تکرار انجام شد. فاکتورهای آزمایش چهار سطح ناقل الکترون (بدون ناقل الکترون، AQS، اسیدهیومیک و اسیدفولویک) و سه سطح باکتری (بدون باکتری،باکتریShewanella sp. و باکتری Pseudomonas aeruginosa) بودند. نتایج نشان داد که تیمار AQS توانست در نبود باکتری، اندازه آهن فرو خاک اسیدی و خاک آهکی را به ترتیب 8 و 7/15 برابر نسبت به اندازه نخستین آهن فرو افزایش دهد که تفاوت معنی داری نسبت به دیگر ناقل های الکترون نشان داد. همچنین بودن باکتری Shewanella sp. در دو خاک اسیدی و آهکی منجر به افزایش 2/7 و 3/16 برابری اندازه آهن فرو شد ولی این افزایش در بودن باکتری P. aeruginosa به 6/5 و 1/12 برابر رسید. نتایج نشان داد که اندازه آهن فرو خاک های اسیدی و آهکی در تیمار باکتری Shewanella sp. و ناقل الکترون AQS به ترتیب 7/11 و 2/22 برابر نسبت به اندازه نخستین آهن فرو افزایش داشت. در تیمار باکتری P. aeruginosa و ناقل الکترون AQS این افزایش به 5/7 و 16 برابر رسید. نتایج نشان دادند که در هر دو خاک اسیدی و آهکی، ناقل الکترون AQS و باکتریShewanella sp.، پیامد سودمند بیشتری بر فرآیند کاهش زیستی در برابر دیگر تیمارها داشتند.
    کلیدواژگان: آهن فریک، باکتری های کاهنده غیرجذبی آهن، کاهش زیستی، ناقل الکترون
  • لیلا جلالی، جواد بذرافشان، علیرضا توکلی صفحات 1661-1672
    تاکنون شاخص های مختلفی مانند شاخص شدت خشکسالی پالمر (PDSI)، شاخص رطوبت محصول (CMI) و شاخص اکتشاف خشکسالی (RDI) برای پایش خشکسالی کشاورزی ارائه شده اند که عموما شرایط کلی رطوبت خاک را به عنوان تابعی از پارامترهای اقلیمی دما و بارش مدل می کنند ولی اختصاص به محصول معینی ندارند. شاخص خشکسالی محصول خاص که بر پایه یک مدل بیلان آبی است جزء شاخص هایی است که تبخیر-تعرق را مستقیما وارد پایش خشکسالی کرده و براساس نسبت تبخیر-تعرق واقعی به تبخیر-تعرق پتانسیل تعریف می شود. در این مطالعه یک مدل شاخص خشکسالی محصول خاص با استفاده از داده های 9 ساله هواشناسی، خاک، عملکرد و فنولوژی محصول گندم ایستگاه کرمانشاه واقع در اقلیم معتدل سرد،مورد واسنجی و اعتبارسنجی قرار گرفت. همچنین، رابطه شدت خشکسالی محصول خاص با یک شاخص واجد طبقه بندی، شاخص اکتشاف خشکسالی،مورد ارزیابی قرار گرفت. مدل بامقدار بالای ضریب تبیین (95/0) و شاخص توافق (748/0) و مقدار پایین RMSE (098/0) و MAE (068/0) در ایستگاه موردنظر بخوبی اجرا شد. همچنین، نتایج حاکی از ارتباط قابل قبول شاخص خشکسالی محصول خاص با شاخص اکتشاف خشکسالی در طول دوره رشد محصول می باشد.
    کلیدواژگان: پایش خشکسالی کشاورزی، شاخص اکتشاف خشکسالی، تبخیر، تعرق، مدل بیلان آب
  • شیده شمس، سید محمد موسوی بایگی صفحات 1673-1685
    اختلاف دامنه ی شبانه روزی دمای هوا یک متغییر هواشناسی است که نقش موثری در تعیین اقلیم هر منطقه دارد. این مطالعه به بررسی تغییراختلاف دامنه شبانه روزی دمای هوا در مقیاس های سالانه، فصلی، ماهانه و روزانه ی شهر مشهد پرداخته است. آزمون هایSNHT، Buishand، Pettitt، Von-Neumann و کندال-تاو برای این منظور مورداستفاده قرار گرفت. نتایج به دست آمده از این مطالعه حاکی از وجود روند کاهشی DTR در طی 60 سال گذشته (2010-1951) در ایستگاه مشهد است. با توجه به نتایج حاصل از این مطالعه مشخص شد که شیب تغییرات در سری زمانیدامنه ی تغییرات شبانه روزی دمای هوای سالانه(DTR) کاهشی است (029/0- درجه ی سانتی گراد در سال). بیشترین میزان تغییرات DTR در فصل پاییز (043/0- درجه ی سانتی گراد در سال) و کمترین آن وابسته به فصل بهار (015/0- درجه ی سانتی گراد در سال) است. همچنین از نیمه ی دوم دهه ی 1980 تا 2010 همان گونه که انتظار می رفت تغییراتDTR روندی کاهشیاست. بررسی آماری اختلاف دمای حداکثر و حداقل ماهانه نیز نشان داد که در طی سال های آماری 1951 تا 2010 DTR روندی کاهشی دارند. نقطه ی شکست در این سری های زمانی نیز همانند سری های فصلی و سالانه در حوالی سال 1985 رخ داده است. روند کاهشی اختلاف دمای شبانه روز حاکی از افزایش بیشتر دمای حداقل در برابر دمای حداکثر است. این امر می تواند بر بخش کشاورزی اثرات قابل توجهیاعمال کند. لذا در یک مدیریت صحیح کشاورزی بایستی چنین مواردی را مدنظر قرار داد.
    کلیدواژگان: دمای حداکثر، دمای حداقل، آزمون های همگنی، مشهد
  • وستا افضلی، مسعودرضا حسامی کرمانی صفحات 1686-1699
    به منظور تبدیل خروجی های بزرگ مقیاس مدل های جهانی به ریزمقیاس، تحت تاثیر متغیرهای محلی مانند دما، به تکنیک های ریزمقیاس نمایی قابل اعتماد نیاز است. روش های کلاسیک ریزمقیاس نمایی آماری با در نظر گرفتن وابستگی زمانی، مدل را اجرا نموده و به شبیه سازی طرح اقلیمآینده می پردازند. در این تحقیقبا کمک مدلASD به ریزمقیاس نمایی چندمکانی پارامترهای دما و بارش با داده های بروز شده ی CGCM3.1 با سناریوی A2 برایدو ایستگاه رشت و بندرانزلی به طور همزمان با در نظرگرفتن همبستگی های چند مکان پرداخته و سپس برای سه دوره ی سی ساله آینده، اقلیم شبیه سازی شد. هدف از استفاده این روش، نشان دادن اهمیت مدل های چندمکانی و ایجاد زمینه ی مناسب برای محاسبه ی عدم قطعیتشبیه سازی های اقلیم آینده است. به منظور انتخاب متغیرهای غالب برای مدل سازی چند مکانی از روش رگرسیون گام به گام استفاده شد؛ به طوری که متغیرهای ارتفاع ژئوپتانسیل سطح 850 هکتوپاسکال، رطوبت ویژه سطح 850 هکتوپاسکال،رطوبت ویژه سطح 1000هکتوپاسکال و دمای سطح در ارتفاع 2 متری مهم ترین متغیرها برای مدل های دما و بارش هستند. نتایجبه طور میانگین افزایش دما و کاهش بارندگی را برای سال های آتینشان می دهد. در ناحیه مورد مطالعه، میزان کاهش در میانگین بارش مقدار 15/0 تا 3/0 میلی متر در روز و کاهش شاخص اقلیمی درصد روزهای مرطوب 6 تا 25/7 درصد نسبت به دوره ی مبنا (1990-1961) برآورد شده است؛ از طرفی افزایش شاخص میانگین دمای حداکثر، میانگین و حداقل به ترتیب 17/3، 5/2 و 1/2 درجه سانتی گراد نسبت به دوره مبنا دیده شده است.
    کلیدواژگان: پیش بینی شونده، پیش بینی کننده، مدل ASD، مدل های اقلیم جهانی
  • محمد قبایی سوق، حمید زارع ابیانه، ابوالفضل مساعدی، سیده زهرا صمدی صفحات 1700-1717
    خشکسالی یک ویژگی طبیعی تکرار شونده از تغییرات اقلیمی می باشد که اساسا در ارتباط با کمبود بارش تعریف می گردد. امروزه همگان پذیرفته اند که خشکسالی یک پدیده ی چند متغیره می باشد و نوسانات هر یک از متغیرهای جوی و اقلیمی می توانند سبب افزایش یا کاهش شدت این پدیده گردد. شاخص نسبتا جدید بارش- تبخیر و تعرق استاندارد شده (SPEI) از داده های بارش و تبخیر و تعرق در قالب یک مدل بیلان آبی بر پایه ی مفاهیم شاخص بارش استاندارد شده (SPI) استفاده می کند و قادر به در نظر گرفتن اثرات ناشی از گرمایش جهانی می باشد. در این تحقیق با بررسی ارتباط بین شاخص SPEI با شاخص های SPI و شناسائی خشکسالی (RDI)، از شاخص SPEI برای پایش خشکسالی 11 ایستگاه واقع در 6 منطقه ی مختلف آب و هوائی ایران در مقیاس های سالانه، کوتاه مدت (1، 3 و 6 ماهه) و بلندمدت (9، 12، 18و 24 ماهه) استفاده شده است. هم چنین به منظور بررسی روند وضعیت های رطوبتی طی 51 سال اخیر (2010- 1960) در کشور از روش گرافیکی LOWESS و آزمون ناپارامتری من– کندال به ترتیب در مقیاس سالانه و ماهانه استفاده شده است. مطابق نتایج بدست آمده بیشترین همبستگی شاخص SPEI با شاخص های SPI و RDI مربوط به ایستگاه های واقع در نواحی مرطوب ساحلی می باشد و با کم شدن مقدار رطوبت، همبستگی آن ها با یکدیگر کاهش می یابد. مقایسه ی نتایج شاخص های SPI و SPEI نشان داد که شاخص SPI ضمن داشتن نتایج مناسب در مناطق مرطوب، در مناطق خشک دقت کمتری دارد. هم چنین بر اساس نتایج شاخص SPEI در مقیاس های بلندمدت، سه دوره ی مشخص رطوبتی در طول 51 سال گذشته قابل تشخیص می باشد که شروع وقایع خشکسالی دوره ی سوم از سال 1997 می باشد. نتایج بررسی روند سالانه وضعیت های رطوبتی نیز نشان دهنده ی تغییرات افزایشی وقوع خشکسالی ها در سال های منتهی به سال 2010 می باشد. از طرفی بررسی روند وضعیت های رطوبتی بر اساس شاخص SPEI یک ماهه نشان می دهد که روند مشاهد شده برای بیشتر ماه های سال (اکتبر تا دسامبر و ژانویه تا ژوئن) در ایستگاه های مورد بررسی به جز تهران و شیراز بیشتر از نوع کاهشی می باشد که نشانگر افزایش کمبودهای رطوبتی طی سال زراعی می باشد.
    کلیدواژگان: خشکسالی، کمبود یا مازاد بارش، آزمون من-کندال، روش LOWESS
  • امیرحسین آقاخانی افشار، یوسف حسن زاده، علی اصغر بسالت پور، محسن پوررضا بیلندی صفحات 1718-1732
    چرخه هیدرولوژی در حوضه رودخانه ها و منابع آب قابل دسترس در مناطق خشک و نیمه خشک جهان به شدت تحت تاثیر تغییرات اقلیم و افزایش بیش از حد انتشار گازهای گلخانه ای قرار دارند؛ به گونه ای که در سال های اخیر، افزایش درجه حرارت ناشی از انتشار بیش از حد گازهای گلخانه ای سبب ایجاد یک ناهنجاری در سیستم اقلیم کره زمین گردیده است. هدف از این تحقیق بررسی فصلی روند تغییرات آتی مولفه های اقلیمی در یکی از بزرگترین حوضه های کوهستانی شمال شرقی ایران (حوضه آبخیز کشف رود) با استفاده از برونداد مدل های گردش کلیسری CMIP5 و تحت سناریوهای جدید انتشار RCP می باشد. در این تحقیق با درنظر گرفتن دو پارامتر بارش و درجه حرارتبه عنوان مهم ترین پارامترهای اقلیمی در حوضه های آبخیز، چهارده مدل از بین مدل هایCMIP5 انتخاب گردید. در دوره تاریخی (1384-1371)، داده های شبیه سازی شده توسط این مدل ها با داده های مشاهداتی و با استفاده از چهار معیار ارزیابی شامل: ضریب ناش-ساتکلیف، درصد اریبی، ضریب تعیین و نسبت جذر ریشه مربعات خطاء به انحراف معیار استاندارد داده های مشاهداتی، مورد مقایسه و ارزیابی قرار گرفتند. در نهایت، چهار مدل اقلیمی به نام های GFDL-ESM2G، IPSL-CM5A-MR، MIROC-ESM و NorESM1-M که براساس معیارهای ارزیابی بیشترین انطباق را با داده های مشاهداتی از خود نشان دادند، انتخاب گردید. علاوه بر این، تغییرات اقلیم آینده توسط چهار سناریوی جدید انتشار (RCPs) به نام های RCP2.6، RCP4.5، RCP6.0 و RCP8.5 و تحت سه بازه زمانی آینده نزدیک (1416-1385)، آینده متوسط (1449-1416) و آینده دور (1479-1449) در این چهار مدل مورد مقایسه و ارزیابی قرار گرفتند. به منظور بررسی روند تغییرات سالانه و فصلی مولفه های اقلیمی از آزمون غیرپارامتری من-کندال استفاده گردید. نتایج حاصل از آزمون من-کندال، نشان داد که مولفه بارش، از یک روند مثبت و منفی که از نظر آماری معنی دار می باشد، پیروی می کند. همچنین درجه حرارت متوسط نیز یک روند مثبتمعنی دار با سطوح اعتماد 90، 99 و 9/99 درصد را از خود نشان داد. بیشترین و کمترین بارش ها در فصل های بهار و تابستان رخ خواهد داد و درجه حرارت متوسط در تمامی فصول سال بیشتر از دوره پایه (تاریخی) می باشد. همچنین، به طور متوسط در تمامی مدل ها و سناریوها، بیشترین و کمترین درجه حرارت متوسط نیز در فصل های تابستان و زمستان حاصل خواهد شد و به تبع آن میزان بارش های فصلی نیز در این فصول به ترتیب کاهش و افزایش خواهد یافت.
    کلیدواژگان: آزمون من، کندال، تغییر اقلیم، سناریوی انتشار، گازهای گلخانه ای، گزارش ارزیابی پنجم
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  • Vahid Rezaverdinejad, M. Shabanialasl, S. Besharat Pages 1334-1346
    Introduction
    Greenhouse cultivation is a steadily developing agricultural sector throughout the world. In addition, it is known that water is a major issue almost all part of the world especially for countries which have insufficient water source. With this great expansion of greenhouse cultivation, the need of appropriate irrigation management has a great importance. Accurate determination of irrigation scheduling (irrigation timing and frequency) is one of the main factors in achieving high yields and avoiding loss of quality in greenhouse tomato and cucumber. To do this, it is fundamental to know the crop water requirements or real evapotranspiration. Accurate estimation on crop water requirement is needed to avoid the excess or deficit water application, with consequent impacts on nutrient availability for plants. This can be done by using appropriate method to determine the crop evapotranspiration (ETc). In greenhouse cultivation, crop transpiration is the most important energy dissipation mechanisms that influence ETc rate. There are a large number of literatures on methods to estimate ETc in greenhouses. ETc can be measured or estimated by direct or indirect methods. The most common direct method estimates ETc from measurements with weighing lysimeters. Thisalsoincludes the evaporation measuring equipment, class A pan, Piche atmometer and modified atmometer. Indirect method includes the measurement of net radiation, temperature, relative humidity, and air vapour pressure deficit. A large number of models have been developed from these measurements to estimate ETc. Due to the fast development of under greenhouse cultivation all around the world, the needs of information on how it affects ETc in greenhouses has to be known and summarized. The existing models for ETc calculation have to be studied to know whether it is reliable for greenhouse climate (hereafter, microclimate) or not. Regression and artificial neural network models are two important models to estimate ETc in greenhouse. The inputs of these models are net radiation, temperature, day after planting and air vapour pressure deficit (or relative humidity).
    Materials And Methods
    In this study, daily ETc of reference crop, greenhouse tomato and cucumber crops were measured using lysimeter method in Urmia region. Several linear, nonlinear regressions and artificial neural networks were considered for ETc modelling in greenhouse. For this purpose, the effective meteorological parameters on ETc process includes: air temperature (T), air humidity (RH), air pressure (P), air vapour pressure deficit (VPD), day after planting (N) and greenhouse net radiation (SR) were considered and measured. According to the goodness of fit, different models of artificial neural networks and regression were compared and evaluated. Furthermore, based on partial derivatives of regression models, sensitivity analysis was conducted. The accuracy and performance of the employed models was judged by ten statistical indices namely root mean square error (RMSE), normalized root mean square error (NRMSE) and coefficient of determination (R2).
    Results And Discussion
    Based on the results, the most accurate regression model to reference ETc prediction was obtained three variables exponential function of VPD, RH and SR with RMSE=0.378 mm day-1. The RMSE of optimal artificial neural network to reference ET prediction for train and test data sets were obtained 0.089 and 0.365 mm day-1, respectively. The performance of logarithmic and exponential functions to prediction of cucumber ETc were proper, with high dependent variables especially, and the most accurate regression model to cucumber ET prediction was obtained for exponential function of five variables: VPD, N, T, RH and SR with RMSE=0.353 mm day-1. In addition, for tomato ET prediction, the most accurate regression model was obtained for exponential function of four variables: VPD, N, RH and SR with RMSE= 0.329 mm day-1. The best performance of artificial neural network for ET prediction of cucumber and tomato were obtained with five inputs include: VPD, N, T, RH and SR. The RMSE values of test data sets for cucumber and tomato ET were obtained 0.24 and 0.26 mm day-1. Moreover, the sensitivity analysis results showed that VPD is the most sensitive parameter on ETc.
    Conclusion
    The greenhouse industry has expanded across many parts of the word and the need of information on a reliable ETc method especially by indirect method is crucial. In this research, the artificial neural network models indicated good performance compared with linear and nonlinear regressions. The evaluated method could be used for scheduling irrigation of greenhouse tomato and cucumber.
    Keywords: Performance Evaluation, Multivariable Regression, Meteorological Variables
  • M. Delfanazari, Atefeh Parvaresh Rizi Pages 1347-1357
    Introduction
    The energy crisis has led the world toward the reduction of energy consumption. More than 70 percent of the energy in agriculture sector is used by pumps. In our country, there is no clear standard and guideline and also no adequate supervision for the design, selection, installation and operation of pumping systems appropriate to the circumstances and needs. Consequently, these systems operate with low efficiency and high losses of energy. While more than 20 percent of the world's electricity is consumed by pumps, average pumping efficiency is less than 40%. So evaluation of pumping stations and providing some solutions to increase efficiency and pumping system’s life time and to reduce energy consumption can be an effective in optimization of energy consumption in the country. The main reasons for the low efficiency of pumping systems comparing to potential efficiency are using unsuitable techniques for flow control, hydraulic and physical changes of pumping system during the time, using pumps or motors with low efficiency and poor maintenance. Normally the amount of flow is not constant over the time in a pumping system and needed flow rate is changed at different times. Designing of pumping system should be responsible for peak requirements as well as it must suggest the suitable flow control method to achieve least energy losses for minimum flow requirements. Also one of the main capabilities to reduce energy consumption in pumping stations is improving the flow control method. Using the flow control valves and bypass line with high energy losses is very common. While the use of variable speed pumps (VSPs) that supply water requirement with sufficient pressure and minimum amount of energy, is limited due to lack of awareness of designers and (or) high initial costs.
    Materials And Methods
    In this study, the operation of the pumping stations under four scenarios (for discharge control) in a drip irrigation system was analyzed and evaluated: A) Pumping station equipped with VSPs, in this case it is possible to regulate energy consumption due to the required discharge and pressure for irrigation system , B) Pumping stations equipped with constant speed pumps (CSPs) and flow control valve maneuver in every decade of irrigation, C) Pumping stations equipped with CSPs without any flow control and D) Pumping stations equipped with CSPs and flow control valve maneuver per month of irrigation. Pumping stations equipped with CSPs was designed for a 100 hectares irrigation area for peach and apple trees in the South West of Isfahan province. The produced pressure under four types of flow control were determined. Then pump performance and energy consumption were evaluated under three operation scenarios (B, C and D) and afterward compared with the performance of VSP stations that was designed for this irrigation system.
    Results And Discussion
    The most important point in the design of pumping stations is energy consumption, because the cost of energy supply is high and the operation should be able to save more energy. Using the output values of pressure and flow rate from developed model, the amount of energy consumption for each pump was calculated. It was observed that the energy consumed in pumping stations equipped with VSPs is significantly less than other stations. Regarding to the total energy consumption and the amount of energy that each scenario can save, the percentage of energy savings were calculated. The results show that the highest percentage of energy savings are belonging to scenario (a) (using VSPs).
    Conclusion
    The results of this study show that application of VSPs at pumping stations than commonly pumping stations with CPSs, depending on the type of CSP operation, saves 44 to 54 percent of energy. Using VSPs, which save a lot of energy compare to other methods, can be an important phase in optimizing energy consumption and minimizing the cost operation of the agriculture pumping station. So the type of operation that discussed in the present study and also the type of irrigation system, pump selection, cultivated area and irrigation scheduling are effective at saving energy during VSPs employment. In a recent case, reduction in energy cost should be independently calculated for each irrigation system and be considered in the lifetime costs of pumping system. Regarding the results of this research and also latest studies, it can be said that the study design and implementation of variable speed pumps in irrigation projects should be considered in national scale. Because development of pressurized irrigation schemes that inevitably need to pump, is the country's main policies for efficient use of water.
    Keywords: Control valve, Energy Losses, Irrigation system, Variable speed pumps
  • Soheila Tofighi, J. M. Vali Samani, S. A. Ayyoubzadeh Pages 1358-1369
    Introduction
    Currently, large dams in the world, due to the high amount of sediments in the reservoir, especially around the intake, have operational problems. One of the solutions for this problem is pressure flushing. In this type of flushing, a mixture of water and sediment is removed from bottom outlets form dam reservoir and a funnel shaped crater is created in the vicinity of the outlet opening. In laboratory experiments carried out in this study, pressure flushing with the expansion of bottom outlet within the reservoir and its statistical analysis of bursting events were investigated. The structure of the turbulent flow is not fully understood due to their complexity and random nature. Klein et al. Introduced the turbulence bursting in this kind of flow and Nezo and Nakagora suggested that the events resulting from turbulence bursting has a significant effect of transferring the sediment particles.
    Materials And Methods
    For the purposes of this study, the experiments were conducted with a physical model with 7m length, 1.4m width, and 1.5m height, consisting of three parts namely the inlet of the model, the main reservoir, and settling basin. The main reservoir of the model was 5m long and the sediments were placed within this part of the model. The sediment particles were non-cohesive silica with uniform size and with median diameter (d50) 1.15mm and geometrics standard deviation (σg) 1.37. Experiments carried out with different discharges and water depths above the bottom outlet in different expansion size of outlet channel in constant sediment level of 20cm above the center of the outlet channel. The model was slowly filled with water until the water surface elevation reached to a desired level. The bottom outlet was manually opened, after a while sedimentwere discharged with the water flow in very high concentrations through the outlet channel (sudden discharge) and a funnel shaped crater was formed in front of it. After the run of each experiment, the bed level of scouring was measured using laser meters, and the volume of flushing cone was calculated by Surfer software. For investigation of turbulence parameters, the measurement of flow velocity in 0.5cm from the bed of flushing cone in the central axis of the outlet channel in the flow rate of 3 liters per second and water level of 47.5cm for three expansion sizes of the outlet channel (10, 20, and 30cm) was performed. The flow velocity measurement was done using an Acoustic Doppler Velocimeter. This device is capable of measuring instantaneous velocity in three directions.
    Results And Discussion
    The results indicated that the relative amount of bottom outlet channel expansion for 0.5, 1 and 1.5 times height of the sediments in the reservoir, leads to increase in flushing cone length for an average of 48, 83 and 113% and flushing cone volume for the average amount of 50, 74 and 96% compared to the case when the outlet channel is not developed. Also the analysis of the turbulence parameters showed that in the nearest axis to the inlet of the bottom outlet channel in which the maximum depth of flushing cone, the occurrence probability of sweep and ejection are maximum and impact angle of moment force due to these events is minimized. However the dominant event here is ejected which was also observed in laboratory experiments the particles were transferred into the channel as suspended load. By increasing the distance from the inlet opening of the channel the occurrence probability of sweep and ejection are decreased and impact angle of moment force due to these events is increased, but again, these two events are the dominant events in this regions and sweep is more important than ejection, that the observations also verify the particles transferred as bed load in these region. Ultimately, it comes to a region where the probabilities of all four events are the same and where the sediment flushing cone reaches the primary sedimentation level that scouring and sedimentation don’t take place there. By increasing the expansion size of the bottom outlet channel, the occurrence probability of sweep and ejections are increased and impact angle of moment force due to these events is decreased .So that at the place of the maximum depth of flushing cone, the probability of ejection in 10cm outlet channel is 0.39 and for 20 and 30cm outlet channels corresponds to 0.44 and 0.47, respectively .
    Conclusions
    In this study, the effect of expansion of bottom outlet channel within reservoir and its statistical analysis of bursting events was investigated. Results showed that, expansion of bottom outlet channel within the reservoir has positive and tangible effects on the size of the flushing cone and quadrant analysis of bursting events showed that the occurrence probability of sweep and ejection are greater than other events in the bed of flushing cone. Also with increasing in the expanding size of outlet channel, occurrence probability of dominant events is increasing and impact angle of turbulent force is decreasing. In fact it can be said that, the factors that cause increased dimensions of the flushing cone with the expansion of the bottom outlet channel within the reservoir are the increase of the occurrence probability of sweep and ejection events and decrease of impact angle of turbulent force to these events.
    Keywords: Flow Velocity, Impact Angle of Turbulent Force, Quadrant Analysis, Scour Hole
  • Masoud Naderi, M. Shayannejad, S. Heydari, B. Haghighati Pages 1370-1381
    Introduction
    Owing to drought, increasing demand for fresh water resources and low water use efficiency, the optimum use of water is essential in the agricultural sector. Therefore, this study was conducted to investigate the effect of different levels of irrigation water on quantitative and qualitative Characteristics of potato (Burren cultivar) and determination of its optimum consumptive use of water under Shahr-e kord environment.
    Materials And Methods
    This study was conducted at the Agricultural Research Center and Natural Resources in Shahr-e kord with longitude and latitude of 32˚18΄ and 50˚51΄ , respectively, in 2013. This experiment was performed in randomized complete block design with 7 treatments consisted of different levels of irrigation water and 3 replications. Different levels of irrigation water were: 40, 55, 70, 85, 100, 115 and 130 % of the soil moisture deficit. Potato seeds (burren cultivar) were planted with distance of 20 cm from each other and furrow width of 75 cm. Irrigation program were performed based on the measurement of soil moisture deficit. The irrigation intervals were considered as a fixed 7 day. Irrigation levels were applied to 105 days after planting and the total growth period was 130 days from planting to harvesting. The samples were taken from the two middle furrows. The evaluated parameters were included weight of tubers per plant, tuber diameter, weight of tuber in seed size, weight of tuber production in a plant in marketable size, tuber dry weight, the starch percent, percent of soluble sugars, nitrogen percent. The starch content was determined by Polarimetry method. The soluble sugars content was measured by Colorimetric method, the nitrogen content was measured by wet digestion method and using the Kjeldahl set. Then, the optimal depth of water consumption in conditions of limited water resources were determined by English method Statistical analysis of data and drawing graphs were done with SAS and EXCEL software, respectively.
    Results
    Discussion
    The effect of different levels of irrigation water on yield was significant at 1%. The yield increased with increase of irrigation water. The minimum and maximum yields were belonged to 40 and 130 % treatments with 13.2 and 45.2 tons per hectare, respectively. Whereas, the results revealed that treatments which recieved100, 115 and 130% of the soil moisture deficit had no significant effect on potato yield at 5% level. Thus, potato yield in 115 and 130% treatments were only 2.3 and 3.9% more than treatment receiving full irrigation, respectively. The potato production function was obtained using the depth of water which consumed during the growing season and yield in each treatment. The results showed that the effect of different levels of irrigation water was significant on yield, starch, soluble sugars, dry matter, irrigation water use efficiency and the weight of tuber production per plant in marketable size As the level of irrigation water increased, the yield, soluble sugars content and weight of tuber per plant in marketable size increased and the starch and dry matter content decreased. Moreover, effect of different levels of irrigation water on nitrogen percent and the weight of tuber in seed size were not significant. Maximum and minimum of irrigation water use efficiency were belonged to 85 and 40% with values of 6.96 and 4.84 Kg m-3, respectively. Maximum and minimum percentages of starch were belonged to 40 and 130% treatments with values of 76.6 and 61%, respectively. The soluble sugar content in potato can causes discoloration and darkness of the product, and accordingly it makes the non-marketability of the product. Maximum and minimum soluble sugar contents were belonged to 130 and 40% treatments with values of 2.12 and 3.07%, respectively. In addition, the increase of irrigation water caused to the increase of weight of tuber per plant in marketable size. Therefore, the highest marketable tuber yield was belonged to 130% treatment and it was 1.5 kg per plant and the lowest one was belonged to 40% treatment and it was 0.61 kg per plant. The applied water which maximized the income was 821 mm during the growth period.
    Conclusion
    The use of 82% full irrigation (533mm) can result in maximum net income and irrigated area can increase by 22% compare to full irrigation. If the purpose of planting is get to the maximum yield, the use of 130% irrigation treatment is recommended and if the purpose is the production of seed potatoes, the use of 85% irrigation, treatment is recommended.
    Keywords: Irrigation water use efficiency, Optimization, Production function, Profit function
  • Moslem Akbarzadeh, Bijan Ghahraman, Kamran Davary Pages 1382-1393
    Introduction
    For water resources monitoring, Evaluation of groundwater quality obtained via detailed analysis of pollution data. The most fundamental analysis is to identify the exact measurement of dangerous zones and homogenous station identification in terms of pollution. In case of quality evaluation, the monitoring improvement could be achieved via identifying homogenous wells in terms of pollution. Presenting a method for clustering is essential in large amounts of quality data for aquifer monitoring and quality evaluation, including identification of homogeneous stations of monitoring network and their clustering based on pollution. In this study, with the purpose of Mashhad aquifer quality evaluation, clustering have been studied based on Euclidean distance and Entropy criteria. Cluster analysis is the task of grouping a set of objects in such a way that objects in the same group (called a cluster) are more similar (in some sense or another) to each other than to those in other groups (clusters). SNI as a combined entropy measure for clustering calculated from dividing mutual information of two values (pollution index values) to the joint entropy. These measures apply as similar distance criteria for monitoring stations clustering.
    Materials And Methods
    First, nitrate data (as pollution index) and electrical conductivity (EC) (as covariate) collected from the related locational situation of 287 wells in statistical period 2002 to 2011. Having identified the outlying data and estimating non-observed points by spatial-temporal Kriging method and then standardizes them, the clustering process was carried out. A similar distance of wells calculated through a clustering process based on Euclidean distance and Entropy (SNI) criteria. This difference explained by characteristics such as the location of wells (longitude & latitude) and the pollution index (nitrate). Having obtained a similar distance of each well to others, the hierarchical clustering was used. After calculating the distance matrix, clustering of 287 monitoring stations (wells) was conducted. The optimal number of clusters was proposed. Finally, in order to compare methods, the validation criteria of homogeneity (linear-moment) were used. The research process, including spatial-temporal Kriging, clustering, silhouette score and homogeneity test was performed using R software (version 3.1.2). R is a programming language and software environment for statistical computing and graphics supported by R foundation for statistical computing.
    Results And Discussion
    Considering 4 clusters, the silhouette score for Euclidean distance criteria was obtained 0.989 and for entropy (SNI) was 0.746. In both methods, excellent structure was obtained by 4 clusters. Since the values of H1 and H2 are less, clusters will be more homogeneous. So the results show the superiority of clustering based on entropy (SNI) criteria. However, according to the results, it seems there is more homogeneity of clustering with Euclidean distance in terms of geography, but the measure of entropy (SNI) has better performance in terms of variability of nitrate pollution index. To prove the nitrate pollution index effectiveness in clusters with entropy criteria, the removal of nitrate index, the results was influenced by location index. Also, by removing index locations from clustering process it was found that in clusters with Euclidean distance criteria, the influence of nitrate values is much less. Also, compared to Euclidean distance, better performance was obtained by Entropy based on probability occurrence of nitrate values.
    Conclusion
    Results showed that the best clustering structure will obtain by 4 homogenous clusters. Considering wells distribution and average of the linear-moment, the method based on entropy criteria is superior to the Euclidean distance method. Nitrate variability also played a significant role in identification of homogeneous stations based on entropy. Therefore, we could identify homogenous wells in terms of nitrate pollution index variability based on entropy clustering, which would be an important and effective step in Mashhad aquifer monitoring and evaluation of its quality. Also, in order to evaluate and optimize the monitoring network, it could be emphasized on network optimization necessity and approach selection. Accordingly, less monitoring network clusters lead more homogeneous. Therefore the optimization approach will be justified from increasing to decreasing. In this case the monitoring costs, including drilling, equipment, sampling, maintenance and laboratory analysis, also reduce.
    Keywords: Clustering, Entropy, Euclidean distance, Groundwater, Linear-moment, Silhouette score, Spatial-temporal Kriging
  • Zeyneb Fathi Tilko, Parviz Fathi, Farzad Hosseinpanahi Pages 1394-1402
    Introduction
    water scarcity is one of the primary problems in arid and semi-arid regions such as Iran. In these regions, increasing water productivity in agriculture sector is inevitable. Water productivity can be increased using the drip irrigation method and application of irrigation strategies such as deficit irrigation. Potato is the major crop in Dehgolan plain. Researches have shown that the potato crops very sensitive to water stress. Sprinkler and furrow irrigation systems are common methods for irrigation of potato crop in Dehgolan plain. In this plain, the main supply for irrigation water is groundwater resources. Due to the falling water table in this plain, high sensitivity of the potato crop to water stress and low efficiency of current irrigation systems in the plain, the use of modern methods such as drip-tape irrigation system is inevitable. Drip tape irrigation is one of the efficient methods to increase water productivity of agricultural crops. In this method, determining the optimal drip tape placement in the soil and irrigation water depth are the important factors for obtaining maximum yield and irrigation water productivity of potato crop. The purpose of this study was to investigate the effect of drip tape placement depth and irrigation level on water productivity of the potato crop (Agria cultivar) in Dehgolan plain of Kurdistan province.
    Materials And Methods
    A field experiment was conducted to evaluate the effect of drip tape placement depth and irrigation water level on water productivity of the potato crop (Agria cultivar) in Dehgolan plain of Kurdistan province in spring season of 2014. The results of water quality analysis showed that the irrigation water has not any limitation to plant growth. The soil texture of the field was silty clay. The experiment was arranged in split plot design based on randomized complete blocks Design with three replications. The main plots and subplots included the irrigation water levels (60, 80, 100 and 120 percent of the potato water requirement) and drip tape placement depth (0, 5, 10 and 15 centimeters), respectively. At the end of the growing season, tuber yield of potato was measured. Measured data were analyzed using statistical software, R.Also, mean comparisons were done using Duncan's test.
    Results
    Discussion
    The results showed that the effect of irrigation water and drip tape placement on yield and water productivity was significant (P= 0.01%). The maximum yield and water productivity of this crop were related to 120 and 60 percent of crop water requirement, respectively. The results also showed that drip tape placement depth equal 15 cm was the depth when using drip tape irrigation system in Dehgolan plain. Economic analysis of different treatments showed that irrigation water depth equal 120 percent of the potato water requirement has higher Benefit–cost ratio than other treatments, but the water produced related to it is minimized. Since the Dehgolan plain faced with an intense water deficit and groundwater level of this plain has lost, so maximizing the amount of water produced in Dehgolan plain is inevitable. The results showed that the applied irrigation water depth equal 60 percent of potato water requirement and installation of irrigation tape at a depth of 15 cm can be achieved highest irrigation water use efficiency of potato in Dehgolan plain.
    The result of this research indicated that tuber yield and water productivity of the potato crop under subsurface drip irrigation systems is higher than surface drip irrigation. The ability of subsurface drip irrigation in the improving of tuber yield could be attributed to the less water lost from the soil surface through evaporation. Subsurface drip irrigation allows maintenance of optimum soil moisture content in the root zone, which improved the water productivity.
    Conclusion
    The results show that the maximum tuber yield of potato was related to 120 percent of the potato water requirement. But the maximum irrigation water use efficiency was related to treatment water equal 60 percent of water requirement and drips tape placement depth equal 15 cm. As a result, recommended to increase the irrigation water use efficiency in Dehgolan plain, deficit irrigation strategies applied. The results also showed that the yield and water productivity of the potato crop in subsurface drip irrigation method is more than surface drip irrigation method. In this way the growth of weed and water loss through evaporation was very low and therefore the plant uses the greater amount of irrigation water.
    Keywords: Deficit irrigation, Micro irrigation, Water crisis, Water use efficiency
  • Reza Sajadifar, Javad Ahadiyan Pages 1403-1414
    Introduction
    In this research the spreading coefficient of dense flow under the jet hydraulic in the surrounding fluids of clean water and at the accepting environment with the low depth and high depth has been analyzed. The analyzed parameters are included of discharge injection, density of contaminating fluid, diameter and angle of the contraction of jet nozzle and shallow and deep water ambient fluid.
    Materials And Methods
    These tests are being conducted in the flume laboratory. The results obtained from the tests show that the circulation coefficient is a function of contaminating density and the depth of the accepting environment, such that with increase in the density, the accepting environment depth coefficient will an increase and circulation and coefficient dispersal with the densities of 15, 30, 50, 200 g/lit, are 0/121, 0/135, 0/153, and 0/196 respectively. On the one hand, in the accepting environment depth it has been shown that increase in the Froude density number up to 30 causes decreases in the circulation and coefficient dispersal and then this coefficient will be used in the constant amount of 0/1.
    Results And Discussion
    Results showed that the profiles taken by the GOSEN distribution function and also coordinate the direction taken compliance with about 8/9% errors. Therefore the amount of dispersion of drained stream with accepted error and the use of accepted axial- radial coordinate have been extracted. The most speed has been taken place in the central line and getting further from the center reduces the speed. On the one hand, along the moving path the limits of Jet reduce which is surrounding conditions. On the other hand, considering the continuity coordination in different places from the jet, and reduction of speed, the dispersion width increases. And also according to the analysis conducted it is clear that speed profiles measured is consistent with Gussein distribution. Generally the flow of the sank jets, which are located at an accepting running flow such as rivers or seas, consisted of two areas, with different equations. These two areas are consisting of area (field) close to the jet and area (field) far from jet. When two fluids with different consistencies interfere with each other, it produces a floating jet. In this phenomenon the effective power consisted of composition of floating powers and the amount of movement. Now, if the injected fluid is heavier than the acceptant fluid, the jet will have a negative floating condition and if it is lighter, the jet will have positive floating condition. Ls are the space between an acceptance static fluid and a homogenous fluid and the amount of momentum is more than the floating charge. If the flow of acceptor fluid and jet are not in the same direction, it shows the jet penetration in the fluid, but if both are in the same direction, in this case Ls shows the limitation of the jet. The power and ability of the jet depend directly on the Frode density number. Since in the Frood number, higher density causes stronger jet with the initial momentum. Since the distribution of coefficient after the Frode density number densimetric 30 will be used at the constant amount, it can be said that the amount before this is the "jet near field and the amount more than this is jet far field. The amounts for diagonals 5, 8.15 mm are 141/9, 225/90, 423/57 mm respectably. Results show that in the acceptor environment with low depth, development of the moving borders is nonlinear with second degree equations. In this condition maximum disposal coefficient is equal to 0/28 and its minimum is 0/095. In a low depth environment it has been seen that in a relatively constant depth increase in the Frode density from 52 to 120 the amount of coefficient dispersal decreases up to 2/7 times. This is when for a constant Frode density, the average increase in the relative depth from 5 to 15 the amount of coefficient dispersal is about 16.5%. Increase in the Frood density number causes decrease in the coefficient dispersal. This decrease is due to increase in the speed of fluid entrance in the jet and more energy drop due to more friction with the fluid jet borders. In the other words, increase in the amount of momentum coefficient dispersal will be reduced. At the constant hydraulic conditions, with increase in the relative depth, acceptor environment coefficient dispersal increases which is due to decrease in the adhesion condition and decrease of the depth. Acceptor environment with low depth initial entering speed increases which is due to increase in the Frode density number in one constant length which causes decrease in the floating parameters. On the one hand, increase in the entering speed the amount of friction with the border and therefore the amount of energy drop increases and cause disturbance in the flow with the moving jet borders.
    Conclusion
    In the low depth acceptor environment with a relative constant depth, the amount of percentage of increase in the density of Frode number decreases. Considering the tests conducted it has been shown that the coefficient of dispersal in the acceptor environment low and high depth are opposite to the Frode density number, which means that with an increase in the density of Frode number, the coefficient dispersal decreases. It is also shown that increase in the depth, causes increase in the coefficient dispersal until it reaches a constant amount. Dependency of coefficient dispersal in relation to Densimetric Frode number and convergence angle show increase in the effect of density of Frode number in the convergence angle.
    Keywords: Dense Pollutant, Flow, Froud number
  • Hamid Reza Mehrabadi, Ahmad Nezami, Mohammad Kafi, Malihe Ahmadifard Pages 1415-1425
    Introduction
    More plains of Iran are located in arid and semi-arid regions and so agricultural production systems depend heavily on water. Recently, the reduction of water resources has become a serious threat for crop production such as cotton planting. Therefore, application of low irrigation methods can be an appropriate method to cope with mentioned condition. In addition, it is vital to identify the cotton cultivars reaction to water deficiency. Sensibility of some cotton cultivars is lower than others. Sensitive cultivars seed cotton yield decreases more than tolerant cotton cultivars. Moreover, some of growth stages in cotton plant are more sensitive to water deficiency stress. For example, flowering stage is more sensitive than vegetative growth stage, and boll number per plant is more effective parameter on yield than boll weight. Ulla and et al (2) showed that there are genetic variations for drought stress toleration in cotton plant. Afshar and Mehrabadi (3) indicated that low irrigation on the basis of 50% and 75% of cotton water requirement had no significant effect on vegetative growth of cotton plant. However, it caused the increase of flower and boll shedding per plant. Application of tolerant cultivars compared with sensitive cultivars can increase seed cotton yield under drought stress condition. Consequently, the aim of this study is to survey yield and related morphological traits reactions in sensitive and tolerant cotton cultivars to different water deficiency levels.
    Materials And Methods
    Two tolerant cotton cultivars (Armagan and Varamin) and two sensitive cotton cultivars (Coker349 and Nazili84) as a subplot at three irrigation levels (as a main plot) using split plot design based on complete block design with three replications were carried out at Agricultural Research Station of Kashmar in 2011. Three levels of water consumption based on Penman-Montith method and using cotton KC coefficients were [33% (I33%), 66% (I66%) and 100% (I100% of water requirement)] that it were take placed using drip irrigation method. Yield and yield components traits such as height, the number of boll per plant, boll weight, flower and boll shedding percent, seed cotton yield, biological yield, earliness percent and harvest index were determined at the end of experiment. Data analysis was carried out using Excel and MSTAT-C software.
    Results And Discussion
    The results showed that although water deficiency stress decreased vegetative components, the amounts of decreasing were higher in tolerant cultivars than sensitive cultivars but, by contrast, the reproductive components of tolerant cultivars indicated lower decreasing than sensitive cultivars under water deficiency stress. For example, Varamin cotton cultivar had more number of bolls per plant than Coker349 as a sensitive cultivar. The results also showed that more retention of boll number per plant was the main factor of cultivars difference as for seed cotton yield. The highest number of boll and flower per plant retention belonged to sensitive cultivars such as Coker349 and Nazili (71.2 and 69 percent, respectively) at 66 percent of water consumption and the lowest number of boll and flower per plant retention were 92.3 percent belonging to Varamin as a tolerant cotton cultivar at full water irrigation treatment. The results indicated that all yield components except boll weight were significantly affected by low irrigation levels. In addition, the results revealed that low shedding of flower and boll and accordingly more retention of boll number per plant and also biomass preservation under drought stress were the main factor in yield of tolerant cultivars in comparison with sensitive cultivars. Biological yield reduction was higher than seed cotton yield under water stress condition. High and significant correlation was observed among yields with boll number per plant, biological yield and harvest index under drought stress. Moreover, there was a significant correlation between yield with plant height and biological yield only in full irrigated treatment. Furthermore, harvest index decreased significantly under drought stress. Harvest index value for Coker349 was significantly lower than other cultivars. Coefficient correlation between harvest index and yield and its components showed that harvest index was more dependent with seed cotton yield to biological yield. Therefore, tolerant cultivars had higher seed cotton yield and also biological yield in comparison with sensitive cultivars. While there was a significant correlation between yield with plant height and biological yield only in full irrigated treatment.
    Keywords: Correlation coefficient, Drought stress, Harvest index, Water requirement, Yield
  • Aida Mehrazar, Jaber Soltani, Omid Rahmati Pages 1426-1439
    Introduction
    Limited water resources and its salinity uptrend has caused reducing water and soil quality and consequently reducing the crop production. Thus, use of saline water is the management strategies to decrease drought and water crisis. Furthermore, simulation models are valuable tools for improving on-farm water management and study about the effects of water quality and quantity on crop yield.. The AquaCrop model has recently been developed by the FAO which has the ability to check the production process under different propositions. The initial version of the model was introduced for simulation of crop yield and soil water movement in 2007, that the effect of salinity on crop yield was not considered. Version 4 of the model was released in 2012 in which also considered the effects of salinity on crop yield and simulation of solute Transmission in soil profile.
    Material and
    Methods
    In this project, evaluation of the AquaCrop model and its accuracy was studied in the simulating yield of maize under salt stress. This experiment was conducted in Karaj, on maize hybrid (Zea ma ys L) in a sandy soil for investigation of salinity stress on maize yield in 2011-2012. This experiment was conducted in form of randomized complete block design in four replications and five levels of salinity treatments including 0, 4.53, 9.06, 13.59 and 18.13 dS/m at the two times sampling. To evaluate the effect of different levels of salinity on the yield of maize was used Version 4 AquaCrop model and SAS ver 9.1 software .The model calibration was performed by comparing the results of the field studies and the results of simulations in the model. In calculating the yield under different scenarios of salt stress by using AquaCrop, the model needs climate data, soil data, vegetation data and information related to farm management. The effects of salinity on yield and some agronomic and physiological traits of hybrid maize (Shoot length, root length, dry weight and crop yield) under different levels of NaCl solution osmotic potential were also investigated by SAS ver 9.1 software. Data's mean comparisons were performed by Duncan's multiple range test. To assess the accuracy of AquaCrop Model for Simulation of the Maize Performance under Salt Stress used from Indicators RMSE, MAE, CRM, NSE, d and Er.
    Results
    Discussion
    The results of RMSE and MAE indices showed that AquaCrop model can simulate maize yield under the salinity stress. Accuracy decreased and crop yield prediction underestimated with increasing salinity from treatment 0 to 18.13 ds/m in the first and second harvest. The highest yield related to salinity treatment of 0 dS/m and the lowest yield related to salinity treatment 18.13 dS/m. yeild simulation error increased by increasing salinity, the highest and lowest error of yield simulation in model respectively related to salinity treatments 18.13 and 0 dS/m. The highest and lowest error was in the first harvest respectively 0.56 and 13.1 percent and in the second harvest respectively 0.42 and 21.79 percent, that in the comparison with the results of studies conducted by Steduto and colleagues on maize is not much different. The results comparison in the first and second harvest showed that soil salinity was increased by increasing irrigation number in second harvest, so the error in second harvest is greater than first harvest and the maximum error is related to treatment 18.13 ds/m in the second harvest 21.79 percent.The coefficient of determination R2 for the first and second harvest is respectively 0.850 and 0.834, that indicates a high correlation between yeild values of measured and predicted by the AquaCrop model. CRM index was negative and near zero in both harvest under Salinity different scenarios. According to CRM value, AquaCrop model was overestimated and the model was simulated maize yield under the salinity stress a little more than measured yield. The d statistic index value is close to unity, indicates that yield values in model is compatible with actual values. NSE index was calculated for the first and second harvest respectively 0.81 and 0.84, that is close to one and showed that the model has suitable performance in the yield simulation. Comparison of means by Duncan's multiple range test and analysis of variance in the software SAS ver 9.1 indicated Salinity has a very significant effect on all traits including shoot length, root length, dry weight and crop yield that all traits were decreased significantly by increasing salinity.
    Conclusion
    Comparison of the results of AquaCrop model and statistical analysis in software SAS ver 9.1 showed that maize yield was reduced with increasing salinity. According to index CRM, AquaCrop model was simulated maize yield under the salinity stress more than measured yield in farm. The results showed that the AquaCrop model simulated well maize yield in moderate and low stress, but accurately simulation slightly decreased in high stress. The results of this study was compared with other research and indicated that the error values of AquaCrop model in Karaj is not much different with the error values of other research.
    Keywords: Crop yield, Modeling, Saline water, Statistical analysis, Water management
  • Farshad Fathian, Ahmad Fakheri Fard, Yagob Dinpashoh, Seyed Saeid Mousavi Nadoushani Pages 1440-1460
    Introduction
    Time series models are generally categorized as a data-driven method or mathematically-based method. These models are known as one of the most important tools in modeling and forecasting of hydrological processes, which are used to design and scientific management of water resources projects. On the other hand, a better understanding of the river flow process is vital for appropriate streamflow modeling and forecasting. One of the main concerns of hydrological time series modeling is whether the hydrologic variable is governed by the linear or nonlinear models through time. Although the linear time series models have been widely applied in hydrology research, there has been some recent increasing interest in the application of nonlinear time series approaches. The threshold autoregressive (TAR) method is frequently applied in modeling the mean (first order moment) of financial and economic time series. Thise type of the model has not received considerable attention yet from the hydrological community. The main purposes of this paper are to analyze and to discuss stochastic modeling of daily river flow time series of the study area using linear (such as ARMA: autoregressive integrated moving average) and non-linear (such as two- and three- regime TAR) models.
    Material and
    Methods
    The study area has constituted itself of four sub-basins namely, Saghez Chai, Jighato Chai, Khorkhoreh Chai and Sarogh Chai from west to east, respectively, which discharge water into the Zarrineh Roud dam reservoir. River flow time series of 6 hydro-gauge stations located on upstream basin rivers of Zarrineh Roud dam (located in the southern part of Urmia Lake basin) were considered to model purposes. All the data series used here to start from January 1, 1997, and ends until December 31, 2011. In this study, the daily river flow data from January 01 1997 to December 31 2009 (13 years) were chosen for calibration and data for January 01 2010 to December 31 2011 (2 years) were chosen for validation, subjectively. As data have seasonal cycles, statistical indices (such as mean and standard deviation) of daily discharge were estimated using Fourier series. Then ARMA and two- and three-regime SETAR models applied to the standardized daily river flow time series. Some performance criteria were used to evaluate the models accuracy. In other words, in this paper, linear and non-linear models such as ARMA and two- and three-regime SETAR models were fitted to observed river flows. The parameters associated to the models, e.g. the threshold value for the SETAR model was estimated. Finally, the fitted linear and non-linear models were selected using the Akaike Information Criterion (AIC), Root Mean Square (RMSE) and Sum of Squared Residuals (SSR) criteria. In order to check the adequacy of the fitted models the Ljung-Box test was used.
    Results And Discussion
    To a certain degree the result of the river flow data of study area indicates that the threshold models may be appropriate for modeling and forecasting the streamflows of rivers located in the upstream part of Zarrineh Roud dam. According to the obtained evaluation criteria of fitted models, it can be concluded the performance of two- and three- regime SETAR models are slightly better than the ARMA model in all selected stations. As well as, modeling and comparison of SETAR models showed that the three-regime SETAR model have evaluation criteria better than two-regime SETAR model in all stations except Ghabghablou station.
    Conclusion
    In the present study, we attempted to model daily streamflows of Zarrineh Rood Basin Rivers located in the south of Urmia Lake by applying ARMA and two- and three-regime SETAR models. This is mainly because very few efforts and rather less attention have been paid to this non-linear approach in hydrology and water resources engineering generally.
    Therefore, two types of data-driven models were used for modeling and forecasting daily streamflow: (i) deseasonalized ARMA-type model, and (ii) Threshold Autoregressive model, including Self-Existing TAR (SETAR) model. Each ARMA and SETAR models were fitted to daily streamflow time series of the rivers located in the study area. In general, it can be concluded that the overall performance of SETAR model is slightly better than ARMA model. Furthermore, SETAR model is very similar AR model, therefor, it can be easily used in water resources engineering field. On the other hand, due to apply these non-linear models, the number of estimated parameters in comparison with linear models has decreased.
    Keywords: Forecasting, Urmia Lake, Hydrological processes, Two, three, regime models, Evaluation criteria
  • A. Vaezihir, Mehri Tabarmayeh Pages 1461-1477
    Introduction
    Ground water as a dynamic and recyclable natural resource in fractured rock terrains are characterized by single and double fracture porosity models. Due to the heterogeneous nature of the medium hydraulic properties of these rocks are mainly controlled by fracturing and influenced by multivariate parameters. This heterogeneity is due to various compactions , density of fractures and degree of weathering. Therefore, regarding the importance of ground water resources in social and economic development, the study of fractured rock aquifers especially in arid and semi-arid regions is of interest. In this paper zoning of aquifers has been carried out according to their potential using concept of overlaying of drastic parameters on groundwater development.
    Materials And Methods
    The study area is located in the southwest of Marivan city, Iran. Due to the existence of sandstone and igneous formations and tectonic activities, fractured aquifers, was probably developed. In this paper, Simple Additive Weighted (SAW) and Analytic Hierarchy Process (AHP) using eigenvectors were used to find ground water resources. In order to evaluate the groundwater potential sources, lithology, fracture density, elevation, slope, aspect, drainage density and land use parameters were considered. For this purpose, layers of these information were provided in the IDRISI and GIS medium and then sorted and weighted using the weighted cumulative integrate AHP and SAW methods. The index of ground water potential sources was determined by multiplying each raster layer by its corresponding weighting factor assigned by the AHP and SAW methods. Finally the potential groundwater zoning map was generated by cumulating the seven individual rating and weighting maps.
    Results And Discussion
    According to the output map of AHP model, 56.8 percent of the total study area had a very high water potential and this includes 94.26 percent with high potential and areas with moderate, low and very low water potential included 22.96, 24.96 and 17.07%, respectively. Regarding to the paired comparison AHP model, despite of direct determination of the weight of the SAW model, weight classes of each criterion were achieved according to the preferred class of all classes to the criteria. It is normal that the results from these two models will be different, so that according to SAW method, 0.73,13.07,30.16,18.65,7.37% of study area included area with very high, high, moderate, low and very low groundwater potential resources, respectively. For validation of two mentioned models (AHP and SAW models), The map of springs location were overlaid on the map of potential sources of groundwater of these two methods and the results showed a good agreement with the model of the position of the spring.
    Conclusion
    In This study the AHP and SAW models were used to finding underground water sources. The results showed that in both methods, highly potential water resources areas were mainly located in the northwest of the study area and the west and southwest area had higher potential water resources relative to the east part of the study area. This could be due to low slope and elevation or may be related to the alluvial deposits which covered upper parts of the hard rock with low thickness and this plays a main role in recharging of hard rock.
    However, comparing the results of the two methods showed that AHP method has better results than the SAW. The result of AHP map showed that the east and center part of the study area had moderate to high groundwater potential which consist of about 50% of area.
    Keywords: Almaneh, Analytic Hierarchy Process, Groundwater potential, Simple Additive Weighted
  • Abdolhossein Ziaeyan, Ali Reza Farahbakhash, Hossein Besharati, Lladan Joukar Pages 1478-1488
    Introduction
    The most abundant of agricultural soils in Iran, are calcareous. In calcareous soils, phosphorus fertilizers use efficiency is low. The usage of soil microorganisms is one of the effective ways to increment the uptake of phosphorus in calcareous soils. This microorganisms using various mechanisms, including the production of plant hormones or the production of organic and inorganic acids to dissolve the insoluble phosphorous compounds. Mycorrhizal symbiosis is also one of the most recognized and important symbiosis relationship found in the world. In a mycorrhizal symbiosis,plants can be able to absorb more nutrients and water from soil and fungus plays a protective role as a growth enhancer and make the plants more tolerable to biotic (pathogens) and abiotic (drought, cold and salinity) stresses .This research conducted to study phosphate solubilizing bacteria and mycorrhiza roles on sorghum growth and phosphorus availability to this plant.
    Materials And Methods
    To achieve the desired goals, a pot experiment was conducted as a factorial in completely randomized design with sixteen treatments in three replications. The treatments were combination of four P levels of zero, 25, 50, and 75 mg kg-1 P2O5 from triple super phosphate source, the two treatments of inoculation and without inoculation of phosphate solubilizing bacteria and the two treatments of inoculation and no inoculation of mycorrizal fungus. Required fertilizers based on initial soil test results were supplied. Accordingly, the same amount of nitrogen, 80 mg kg-1 (30 mg kg-1 before planting and 50 mg kg-1 after planting twice) as urea source, 10 mg Zn kg-1 and 5 mg kg-1 Cu per kg soil as the forms of Zinc sulphate (ZnSO4.7H2O) and copper sulphate (CuSO4.H2O) were added to each soil sample. Required Phosphorus also was calculated based on treatments and added to potting soil. Each pot size was 5 kg. every sample was thoroughly mixed and then were placed in pots. At the same time the seeds were inoculated. In harvesting time, some parameters such as plant height and diameter, wet and dry foliage yield, and phosphorous uptake were measured and analyzed statistically. After harvesting time also soils phosphorous content were measured and analyzed.
    Results
    Discussion
    The results indicated that by utilizing the phosphate solubilizing bacteria, stem diameter, dry matter yield, phosphorous uptake, and soils phosphorous content after harvesting significantly increased. These findings indicated that the use of phosphate solubilizing bacteria affected plant growth. Such results have been previously reported. Ramezanian (31) reported that application of PGPR will be increase wheat stem height and diameter. Li et al (18) and Larsen et al (16) reported that soil microorganisms, including growth promoting bacteria through a variety of mechanisms such as ACC deaminase production or an increase in available phosphorus can stimulate plant growth and increase height and diameter of the stem. Glick et al (13) showed that plant growth promoting bacteria through the production of plants hormones increases plant height and stem diameter, and ultimately improve plants yield. Increases yield of plants through the use of phosphate solubilizing bacteria previously has been reported by other studies. Mycorrizal inoculation also had a significant effect (P
    Keywords: Biofertilizers, Calcareous soils, Chemical fertilizers, Soil microorganisms
  • Ali Afshari, H. Khademi, Sh. Ayoubi Pages 1489-1501
    Introduction
    Heavy metals are found to be one of the major environmental hazardous contaminants, for human health, animal life, air quality and other components of environment. They can affect geochemical cycles and accumulate in animal tissues since physical processes are not able to remove them, so they are consistent in long term. The analysis of the total concentration of heavy metals in soil may provide information about soils enrichment but in general, it is widely used to determine the potential mobility of heavy metals in environmental behavior under chemical forms of metals in soils. Heavy metals existat several phases including water-soluble, exchangeable, bounded to organic matter, bounded to carbonates, bounded to Fe-Mn oxides, secondary clay minerals and residual fraction within primary minerals network. There is a dynamic equilibrium between different fractions of elements in soil. The main objectives of the present study were a) The analysis of the total concentration of heavy metals such as Fe, Mn, Ni, Cr, Co, Pb, Zn, Cd and Cu and b) The fractionations of heavy metals and identification of controlling factors to distribution and behavior of heavy metals in soils at different land uses.
    Materials And Methods
    The study was performed at central area of Zanjan province (Iran). The study area was over 2000 km2 in coordinates 20´ 36° to 41´ 36° E and 19´ 48° to 53´ 48° N. The average altitudes were over 1500 meters above sea level. The major land uses of the study area included agriculture (AG), rangeland (RA) and urban (UR). Sample collection was done based on the random grid method in August 2011. Surface soil samples (0-10 cm depth) were taken from grid centers included 137, 77 and 27 samples from AG, RA and UR land uses, respectively. The samples were digested in Nitric acid 5 normal (Sposito et al., 1982) and total concentration of Pb, Zn, Ni, Mn, Cu, Cr, Fe and Co were measured by Perkin-Elmer: AA 200 atomic absorption instrument and cadmium was measured by atomic absorption equipped with Rayleigh: WF-1E graphite furnace. 75 soil samples were selected, DTPA-extraction and sequential extraction were performed and physiochemical characteristics of these samples analyzed. To extract the metals by DTPA, the method developed by Lindsay and Norvell, (1978) was used and sequential extraction was done by Tessier et al., (1979) method. All statistical parameters were calculated using SPSS 16.0 software, and mean comparison (mean separation) was carried out using Duncan test at probability level of 5%.
    Results And Discussion
    The results indicated that heavy metals concentrations and patterns were evidently affected by different land uses. Co concentration was between 17.0 – 35.7 mg/kg and had the lowest total coefficient of variation (14%). The maximum total Cr and Ni values were measured in AG land use (26.1 and 52.6 mg/kg, respectively) and lowest was in UR land use (17.0 and 37.2 mg/kg, respectively). The highest total average value of Mn was found in RA (698.9 mg/kg) and the lowest in UR (629.1mg/kg) land use. The highest Fe concentrations were measured in AG and RA land uses (17.2 and 17.0 g/kg, respectively) and the lowest in UR land use (14.0 g/kg). The maximum Concentration of total Cd was observed in UR land use (2.47 mg/kg) and its minimum values were found in RA and AG (0.83 and 0.75 mg/kg, respectively) in the study area. In UR land use, Cu and Zn were more significant than AG and RA land uses. Pb variation was the same as Zn so that its increased concentration was found in urban land use (90.2 to 1357.5 on average 220.1 mg/kg). The highest Pb values were measured in UR land use (220 mg/kg) while the lowest concentrations were found in RA and AG land uses (80.6 and 69.0 mg/kg, respectively).
    Different elements showed various fractional distribution in different land uses. The highest Co percentage was related to residual fraction at all land uses, with values up to 48.4%, 54.0% and 48.1% in AG, RA and UR land uses, respectively. Ni fractionation had approximately the same pattern with Co in all factions and land uses, except exchangeable fraction of Ni that showed the lowest percentage in all land uses. The dominant fraction of Cu was residual fraction with the amounts of 73.3% 76.0% and 61.9% in AG, RA and UR land uses, respectively. The second dominant fraction in UR and AG land uses was related to that was bounded to OM, with 16.5% and 10.1%, respectively. Zn distribution in the AG and RA land uses had the same trend: Residual>bounded to Fe-Mn oxides>bounded to OM>bounded to carbonate>exchangeable fraction. Whereas, Zn distribution showed different trend in UR land use as bounded to Fe-Mn oxides>residual>bounded to carbonate>bounded to OM>exchangeable fraction. Pb distribution was different in each land use. Pb showed similar distribution to Zn in UR. In AG and RA land uses residual fraction of Pb was measured as highest value while other fractions of Pb had these distributions: Pb bounded to carbonate>bounded to Fe-Mn oxides>exchangeable >bounded to OM fraction in AG land use and Pb bounded to Fe-Mn oxides>bounded to OM>bounded to carbonate>exchangeable fraction in RA land use.
    Conclusion
    Based on the results of this study, Cr, Co, Ni, Mn and Fe magnitudes are uneven in soils. The total heavy metal concentrations fractionation can provide information on the contaminant metals sources. High levels of exchangeable fractions, acid soluble and easily reducible perhaps indicates anthropogenic activities. Naturally, Chemicals are associated to resistant soil fractions such as oxy hydroxides, organic matter and sulfides. In soil fractionation, the contribution of each fraction in soil was a function of metal type and land uses. Those metals were affected by anthropogenic activities such as lead, zinc, and partly copper, showed the highest percentage in the fraction that influenced by external input sources. Those were characterized by lithogenic origin (cobalt and nickel) was mainly found to be highest in residual fraction. However, in all metals, those fractions affected by anthropogenic activities (non-resistant fractions) were much more in urban land use than agriculture and rangeland ones.
    Keywords: DTPA-extraction, Land Use, Sequential extraction, Soil Contamination
  • Saeed Bagherifam, A. Lakzian, A. Fotovat, R. Khorasani Pages 1502-1514
    Introduction
    Arsenic is a highly toxic metalloid in group 15 of periodic table. The information on environmental behaviour of arsenic, however, is still scarce. Contamination of soils and water with arsenic and antimony due to their widespread industrial application and mining activities has raised serious environmental concerns. Nearly all Arsenic-contaminated soils results from human activities and it has different environmental and sociological impacts. Various strategies and methods have been proposed for environmental management and remediation of contaminated soils. Among all methods, the phytoremediation is receiving more attention due to its cost effective and environmental friendly characteristics. In the case of arsenic contaminated soils, there are effective factors such as soil fertility, nutrients content and microorganisms function, which can improve the uptake of As by plants. Up to now, several studies have been evaluated the effects of symbiotic fungal association in plants on increasing nutrients and toxic elements uptake. Many of authors reported that the mycorrhizal symbiosis increases the uptake of toxic elements in root and shoot of plants and consequently improve the efficacy of phytostabilization and phytoextraction processes. There are conflicting results about the effect of arbuscular- mycorrhizal fungi (AMF) on As uptake by various plants. Chen et al. (4) found that Glomus mosseae symbiosis with plant reduces As concentration and enhance phosphorus content in shoot and root of plant. Whilst Cozzolino et al. (7) reported that the AMF increases as concentration in shoot and root of cabbage. Phosphorus has important role on mycorrhizal symbiosis and also As uptake by plants. Therefore, current study was conducted to evaluated effect of Glomus intraradices and Glomus mosseae symbiosis with sunflower and also soil phosphorus concentration on uptake of arsenic from arsenite and arsenate contaminated soils.
    Materials And Methods
    The soil sample (Typic Haplorthids) was collected, air dried and passed through 2 mm sieve and then were heated in 80 centigrade degree temperature for two times. A pot experiment was conducted in a completely randomized design with factorial arrangement and three replications in greenhouse condition. The experimental factors included two species spices of inorganic As (50 mg kg-1 of Arsenite and Arsenate), two levels of phosphorus (0 and 60 mg Kg-1) and three spices of arbuscular mycorrhizae (control, Glomus intraradices and Glomus mosseae). Soil samples spiked with Na2HAsO4.7H2O, NaAsO2 (Arsenite and Arsenate) and Ca (H2PO4)2 (phosphorus) and incubated in greenhouse condition for 4 week. Sunflower seeds were planted and seedlings harvested after 60 day of sowing and then dry weight of sunflower, concentration of As and phosphorus in shoot and root of plant and root colonization percentage determined using standard methods.
    Results And Discussion
    The results revealed that Glomus intraradices (GI) and Glomus mosseae (GM) symbiosis significantly (P
    Keywords: Arsenite, Arsenate, Phytostabilization, Phytoremediation, Mycorrhizae fungi
  • A. Bayat, M. H. Farpoor, A. Jafari Pages 1515-1530
    Introduction
    Soil genesis and development in arid and semi-arid areas are strongly affected by geological formations and geomorphic surfaces. Various morphological, physical, and geochemical soil properties at different geomorphic positions are usually attributed to different soil forming factors including parent material and climate. Due to variations in climate, geological formations (Quaternary, Neogene and Cretaceous) and geomorphology, the aim of the present research was the study of genesis, development, clay mineralogy, and micromorphology of soils affected by climate, geology and geomorphology in Bardsir area, Kerman Province.
    Materials And Methods
    The study area, 25000 ha, starts from Bardsir and extends to Khanesorkh elevations close to Sirjan city. The climate of the area is warm and semi-arid with mean annual temperature and precipitation of 14.9 °C and 199 mm, respectively. Soil moisture and temperature regimes of the area are aridic and mesic due to 1:2500000 map, provided by Soil and Water Research Institute. Moving to west and southwest, soil moisture regime of the area changes to xeric with increasing elevation. Using topography and geology maps (1:100000) together with Google Earth images, geomorphic surfaces and geologic formations of the area were investigated. Mantled pediment (pedons 1, 3, 7, and 8), rock pediment (pedon 2), semi-stable alluvial plain (pedon 6), unstable alluvial plain (pedon 5), piedmont plain (pedons 9 and 11), intermediate surface of alluvial plain and pediment (pedon 4), and old river terrace (pedon 10) are among geomorphic surfaces investigated in the area. Mantled pediment is composed of young Quaternary sediments and Cretaceous marls. Rock pediments are mainly formed by Cretaceous marls. Quaternary formations are dominant in alluvial plains. Alluvial terraces and intermediate surface of alluvial plain and pediment are dominated by Neogene conglomerates. Siltstone, sandstone, and Neogene marls together with Neogene conglomerates are among dominant geological formations of piedmont plain. Eleven pedons affected by young Quaternary sediments, Neogene and Cretaceous marls in aridic, aridic border to xeric, and xeric moisture regimes on above-mentioned geomorphic surfaces were described and sampled using Natural Resources Conservation Service (2012) guideline. Physicochemical properties, clay mineralogy, and micromorphology of soil samples investigated and soils were classified by Soil Taxonomy (2014) and WRB (2015) systems.
    Results And Discussion
    Calcic, gypsic, argillic, and cambic diagnostic horizons investigated after field and laboratory studies. Typic Calcigypsids, Lithic Torriorthents, Typic Haplogypsids, Typic Haplocalcids, Typic Torrifluvents, Sodic Haplocambids, Typic Calciargids, and Xeric Haplocalcids subgroups were found using Soil Taxonomy (2014) system. Gypsisols, Calcisols, Luvisols, Cambisols, and Regosols reference soil groups identified by WRB (2015) classification system. Developed Alfisols, formed on piedmont plain geomorphic surface in xeric moisture regime. On the other hand, Entisols formed on rock pediments with aridic moisture regime. Soils in aridic moisture regimes were little developed with gypsic horizon, and where calcic horizon was formed, it was near the surface. Moving to the west with increasing humidity, gypsum was leached from the pedon and clay illuviation caused argillic horizon to be formed. Formation of Btk horizon in pedon 9 was attributed to a more paleoclimate. The maximum gypsum content of 44.7 % (gypsiferous soils) was found in soils affected by Quaternary formations and Cretaceous marls, but the maximum calcium carbonate (44 %, calcareous soils) was investigated in soils formed on Neogene conglomerate formations. Moreover, the maximum sodium adsorption ratio (SAR) content (29.2 (mmol(±) L-1)0.5) was determined for soils on unstable surface of alluvial plain. Smectite, vermiculite, illite, kaolinite, and chlorite clay minerals were investigated and smectite to illite ratio increased moving from aridic to xeric moisture regimes that prove the pedogenic source of smectite from weathering of illite. Coating and infilling of calcium carbonate, lenticular and interlocked plates and infillings of gypsum, and clay coatings were observed during micromorphological investigations. Micromorphological observations also showed that gypsum crystals decreased and calcite crystals and thickness of clay coatings increased from aridic to xeric moisture regimes. The minimum amount of gypsum crystals was found in Neogene formations. The results also showed that gypsum pedofeatures are dominant in Cretaceous formations, but calcium carbonate pedofeatures are the main features of Neogene formations. Due to presence of animal voids (channel, regular and star-shaped vughs, chamber, and vesicles), spongy microstructure was formed in agricultural lands.
    Conclusion
    Results of the research showed the important role of parent material, climate, and geomorphic surface on genesis and development of soils in Bardsir area.
    Keywords: Argillic, Central Iran, Climolitosequence
  • Mostafa Pajohannia, Mostafa Chorom, Siroos Jafari Pages 1531-1542
    Introduction
    Iron is found in different forms in the soil. In the primary minerals, iron is found as Fe3 or Fe2 which converted to Fe2 and released in unsuitable reduction conditions. Minerals such as sulfide or chlorine and bicarbonate can affect and change the different forms soil Fe. FeAs these elements are abundance in groundwater or soil, they are capable to react chemically with Fe and change different Fe forms and also may deposit or even leach them by increasing its solubility in the soil. Water table fluctuation is a regular phenomenon in Khuzestan that Fe forms change under these situations. The study of Fe oxide forms and its changes can be applied for evaluation of soil development. Therefore, the aim of this study is the water table fluctuation and its quality effects, and some physio-chemical properties on Fe oxides forms in non-saline and saline soils in Khuzestan.
    Materials And Methods
    Soil samples were collected from two regions: saline (Abdolkhan) and non-saline (South Susa) regions. soil samples were collected from all horizons of 12 soil field studied profiles . The samples were analyzed for soil texture, pH, EC (soil: water ratio 1:5), organic carbon and aggregate stability (Kemper and Rosenau method). Fe forms also were extracted by two methods in all samples: di-tyonite sodium and ammonium oxalate extraction. Fe oxalate extracted was related to Feo (non crystal Fe) and Fed-Feo was related to Fec (crystalline Fe). The Fe content were determined by atomic absorbtion spectrophotometer (AAS). Data were analysis in SAS and Excel software and results were presented.
    Results And Discussion
    The results showed that texture were loamy sand to silty clay loam, OM was very poor (0.1-0.7%). The soil salinity was also 2.8-16.8 dS/m. Calcium carbonate equivalent was 38-40%. All pedons were classified in Entisols and Inceptisols according to Keys to soil taxonomy (2010). The results showed that the proportion of Fe with oxalate to di-tionite treatments was different regarding the salinity, texture, organic matters, cultivation and the water table fluctuation. The total Fe content in the middle layers had permanently increased due to the groundwater fluctuation levels and this caused the creation of mottle in this layer. All saline soils had saline subsurface water. The salinity has caused that the effective microorganisms have not been actived on the reduction processes in some profiles and the Fe deposit more in the Fe3纊. The Fe was found more in non-crystal form in saline regions, but it was in the crystal form in non-saline regions which indicated the suitable conditions for Fe’s nodule formation. For example, when soil salinity decreased from 14.9 to 8.1 dS/m, Fec increased from 460.1 to 497.8 mg/kg soil. With increasing the amount of clay, and cultivation periods, the Fed content has also been increased. The Feo/ Fec ratio in undevelopted soils was higher than developed soils. This ratio was low in non-saline soil and was high for saline soil. this indicates that non-saline soil had more development than saline soils. The maximum amount (1.6) was belonged to saline soil and minimum was for no saline soils. With increasing in soil age, tillage periods and clay content this ratio was decreased., statistical analysis Also showed that there was significant difference between Fec and Feo in saline and no saline soils. Also, with increasing in salinity, Fec content decreased and Feo increased. aggregate stability was also increased with increasing Fec content.
    Conclusions
    The Feo content was more in surface of saline soil than subsurface when pedon was ponded and saturated from surface. Feo was very higher in saline soils than no saline soils. Fec had not significant difference between saline and nonsaline soils. Salinity decreased Fec and increased Feo content in soils. Feo/Fec ratio of saline soils was 4 to 5 times fold of non-saline soils. Increasing Feo/Fec ratio in saline soils and decreasing in this ratio in nonsaline soil showed that nonsaline soils had more development than saline soils. Organic matter was more effective in Feo and Fec contents in nonsaline soil than saline soils. Also, Fec content increased with increasing clay content in all horizons that this shows that mottling and more Fe concentration in nonsaline soils.
    Keywords: Fe Crystal, Mottle, Salinity, Subsurface Water
  • Hossein Banejad, H. Banejad, F. Mohsenzadeh Pages 1543-1555
    Introduction
    Pesticides are considered as the most important pollutants in surface water and groundwater. Neonicotinoids are new group of insecticides, derived from nicotine. Their physicochemical properties render them useful for a wide range of application techniques, including foliar, seed treatment, soil drench and stem applications. Confidor, the representative of the first generation of neonicotinoid insecticides, was patented in 1985 by Bayer and was placed on the market in 1991. The Canadian Pest Management Regulatory Agency considers confidor to have high potential for surface water contamination, leaching to groundwater and persistence in soils. Biodegradation is one of the most effective ways to destroy pesticides in the environment. The application of Bioremediation techniques is taken into consideration as an option to reduce or remove pollutants from the environment due to their low cost, high efficiency and environmentally friendly features. Bioremediation by using microorganisms has not any adverse effect after cleanup. The accumulator microorganism species, haven’t pathogenic properties and aren’t the cause of disease on the other organisms. The selection of a biomass for using in bioremediation is very important, it should be abundant in environment and adapted to environmental conditions. The aim of this study was to investigate the ability of various species of Trichoderma fungi to remove Confidor from contaminated water influenced by variables like pH, concentration of the confidor and time.
    Materials And Methods
    In order to conduct this study three different fungal species belonging to the genus Trichoderma were used. The samples were transferred to PDA (Potato Dextrose Agar) sterile solid media for in vitro testing usage. The samples were kept in refrigerator at 4◦C temperature, after the fungal biomass reached to maximal growth; the colonies were transferred to new media and used in our experiments as resources. After complete fungal growth on the solid media, liquid media were prepared with the formula containing 250 g/l potato extract, 20 g/l dextrose and 0.25 g/l Tetracycline antibiotic (to prevent bacteria growth) in three pH (5,7,9) and three toxicant concentrations (1, 3 and 5 mg/l). Lactic acid and KOH (3%) were used to adjust pH in the prepared media. The degradation experiments were performed in a 50 ml falcon for 1 month. All experiments were maintained under similar conditions. The samples were shacken daily. After 1 month of incubation, aliquots (2 ml) were removed; centrifuged and the supernatants were used for the estimation of concentration of residual confidor by spectrophotometer. The results were analyzed by SPSS software.
    Results And Discussion
    According to the results T.harzianum with 60.34% confidor removal had the highest ability and T.tomentosum with 44.60% had the lowest ability to biological degradation of confidor from the polluted waters. The maximum confidor removal (75.89%) using T.harzianum was accrued to acidic media with 5 mg/l of confidor. The minimum confidor removal (53.09%) using T.asperellum was accrued to alkaline media with 1 mg/l of confidor. Using T.tomentosum the efficiency of confidor removal in media with pH=5 and concentration of 5 mg/l was increased by 10.95% and 15.63% compared to the environments with the concentrations of 3 and 1 mg/l, respectively. In the media containing T.harzianum, the percentage of confidor removal after 4 weeks was increased by 46.21% Compared to the first week. In the media containing T.harzianum, T.asperellum and T.tomentosum, the percentage of confidor removal after 4 weeks was increased by 46.21%, 37.06% and 32.84% respectively, Compared to the first week. Totally, the results showed that all the fungi species are capable to remove confodor. Toxicant concentration increasing from 1 mg/l to 5 mg/l, results in increasing the percentage of toxicant removal. The results of confidor removal from mediums with different pH demonstrated that in all studied fungi, toxicant removal at pH=5 is higher than other pH. The results obtained from this study confirm the hypothesis of positive effect of passing the time on confidor removal efficiency by different Trichoderma species.
    Conclusions
    In general, we can conclude that three species of studied Trichoderma in this research can be applied for bioremediation of agricultural waters which are contaminated by confidor. As a result, by collecting the agricultural water that are contaminated with confider and application of these fungi as biological purifiers, we will access to a considerable amount of non-conventional water resources to irrigate of downstream. It is noteworthy that Trichoderma species in addition to the biorefinery potential of pollutants , are able to improve soil structure and increase plant resistance.
    Keywords: Agricultural sewage, Bioremediation, Fungi, Imidacloprid
  • V. Feiziasl, A. Fotovat, A. Astaraei, A. Lakzian, M.A. Mousavi Shalmani, A. Khorasani Pages 1556-1573
    Introduction
    Nitrogen (N) is one of the most important growth-limiting nutrients for dryland wheat. Mineral nitrogen or ammonium (NH4) and nitrate (NO3−) are two common forms of inorganic nitrogen that can serve as limiting factors for plant growth. Nitrogen fertilization in dryland area can increase the use of soil moisture, and improve wheat yields to some extent. Many researchers have been confirmed interactions between water stress and nitrogen fertilizers on wheat, especially under field conditions. Because of water stress affects forms of nitrogen uptake that leads to disorder in plant metabolism, reduction in grain yield and crop quality in dryland condition. On the other hand, use of suitable methods for determining nitrogen requirement can increase dryland wheat production. However, nitrogen recommendations should be based on soil profile content or precipitation. An efficient method for nitrogen fertilizer recommendation involves choosing an effective soil extractant and calibrating soil nitrogen (Total N, NO3− andNH4) tests against yield responses to applied nitrogen in field experiments. Soil testing enables initial N supply to be measured and N supply throughout the season due to mineralization to be estimated. This study was carried out to establish relationship between nitrogen forms (Total N, NO3− andNH4) in soil and soil profile water content with plant response for recommendation of nitrogen fertilizer.
    Materials And Methods
    This study was carried out in split-split plot in a RCBD in Dryland Agricultural Research Institute (DARI), Maragheh, Iranwhere N application times (fall, 2/3 in fall and 1/3 in spring) were assigned to the main plots, N rates to sub plot (0, 30, 60 and 90 kg/ha), and 7 dryland wheat genotypes to sub-sub plots (Azar2, Ohadi, Rasad and 1-4 other genotypes) in three replications in 2010-2011. Soil samples were collected from 0-20, 20-40, 40-60 and 60-80 cm in sub-sub plots in shooting stage (ZGS32). Ammonium measurement in the soil KCl extracts was down by spectrophotometry method and colorimetric reaction at 655 nm. Also, Absorption spectrophotometry method was used for determination of nitrate in soil extract based on its UV absorbance at 210 nm. In this method two measurements were carried out; one before (by Zn coated by Cu) and second after reduction of nitrate). Using the difference between these two measurements, concentration of nitrate in the extracts was determined. Soil water content was also measured with Diviner 2000 after calibration in 0-20, 20-40, 40-60 and 60-80 cm soil profile in sub-sub plots. After wheat harvest, the most suitable regression model between soil mineral nitrogen (Nm) and soil moisture (θ) was fitted with wheat grain yield by DataFit version 9.0 software.
    Results And Discussion
    The best model between soil N forms (nitrate, ammonium and mineral nitrogen) was calibrated between mineral nitrogen (Nm) and soil moisture (θ) with crop response (Y=a_m ln⁡〖(θ)〗_m^2穙⁡〖(θ)〗^2_m ln⁡〖(θ)〗) that explained 80% of dryland wheat yield variations. In this model, the contributions of mineral nitrogen (NO3− 㑾) were 26%, soil moisture 50% and their interactions 24%. According to this model, the effect of soil moisture on production of grain yield was 2.3 folds greater than the mineral N. These results are most suitable for sampling and calibration of mineral nitrogen in 0-40 cm in dryland wheat stem elongation (ZGS32). Critical value of soil mineral N was 41 kg/ha, equal to 18.0 mg Nm/kg in this layer for obtaining higher grain yield (over 2500 kg/ha). According to regression model, application of 50 kg N/ha in autumn was able to provide Nm critical level in 0-40 cm layer for dryland wheat genotypes under experimental conditions. Also simulation model showed that nitrogen fertilizer increased grain yield and it is more than the soil mineral nitrogen. If the soil mineral nitrogen is 20 kg/ha or less in 0-40 cm soil layer, there may be increase of grain yield up to 4000 kg/ha through the application of nitrogen fertilizers. Therefore, increasing of mineral nitrogen in the soil profile up to 20 kg/ha is not appropriate for wheat production in Northwest of Iran drylands.
    Conclusion
    It can be concluded that, there is a relationship between soil nitrogen and moisture content with dryland wheat response and suggested model can be used for nitrogen recommendations for dryland wheat. According to the model, the effects of nitrogen fertilizer application on grain yield were much more than the effect of soil mineral nitrogen. Therefore, the increasing of soil nitrogen storage is not recommended in dryland conditions.
    Keywords: Critical Level, Nitrogen Requirement, Simulation, Wheat Genotype
  • Vahid Moradinasab, Mehran Shirvani, Sh. Ayoubi, Mohammad Reza Babaei Pages 1574-1583
    Introduction
    Water shortage in arid and semiarid regions of the world is a cause of serious concerns. The severe water scarcity urges the reuse of treated wastewater effluent and marginal water as a resource for irrigation. Mobarake Steel Complex has been using treated industrial wastewater for drip-irrigation of trees in about 1350 ha of its green space. However, wastewater may contain some amounts of toxic heavy metals, which create problems. Excessive accumulation of heavy metals in agricultural soils through wastewater irrigation may not only result in soil contamination, but also affect food quality and safety. Improper irrigation management, however, can lead to the loss of soil quality through such processes as contamination and salination. Soil quality implies its capacity to sustain biological productivity, maintain environmental quality, and enhance plants, human and animal health. Soil quality assessment is a tool that helps managers to evaluate short-term soil problems and appropriate management strategies for maintaining soil quality in the long time. Mobarakeh Steel Complex has been using treated wastewater for irrigation of green space to combat water shortage and prevent environmental pollution. This study was performed to assess the impact of short- middle, and long-term wastewater irrigation on soil heavy metal concentration in green space of Mobarake Steel complex.
    Materials And Methods
    The impacts of wastewater irrigation on bioavailable and total heavy metal concentrations in the soils irrigated with treated wastewater for 2, 6 and 18 years as compared to those in soils irrigated with groundwater and un-irrigated soils. Soils were sampled from the wet bulb produced by under-tree sprinklers in three depths (0-20, 20-40 and 40-60 cm). Soil samples were air-dried, and crushed to pass through a 2-mm sieve. Plant-available metal concentrations were extracted from the soil with diethylenetriaminepentaacetic acid-CaCl2-triethanolamine (DTPA-TEA). To determine the total concentration of heavy metals, the soil samples were digested in 6 M HNO3. Concentrations of heavy metals in the extracts were determined by Atomic Absorption Spectroscopy. Finally, available metal micronutrient levels in the soil were compared with the critical deficiency ranges suggested for calcareous soils. Also, total concentrations of the metals in the soils were compared with the standards of the Iranian Environmental Protection Agency to assess possible contamination of soils with heavy metals in the studied area.
    Results And Discussion
    The results of this study showed significant increases of plant-available Fe in the soils irrigated with wastewater for 6 and 18 years as compared to the unplanted control. Regardless of the type of irrigation water used, available Mn and Ni were significantly increased in all forested areas as compared to the unplanted soils. Available Zn fraction was significantly higher in the soils with history of 6 and 18 years of wastewater irrigation. Increase in available Cu concentration was statistically significant only in the soils irrigated with wastewater for 18 years. As the metal concentration in the wastewater used for irrigation was very low, it seems that the major source of metal accumulation in the soils is particulate fallout or emissions directly from the dump sites and metal plating operation. Furthermore, irrigation and forestation practices might have improved bioavailability of micronutrient metals in the soils of green space of Mobarakeh Steel complex through increasing organic matter content of the soils which enhances metal chelation reactions.
    Total concentrations of the metals in the forested soils also increased as compared to those of the control. Total Fe, Mn, and Zn concentrations were notably higher in all soils of the green space area as compared to those in the unplanted control sites. Wind-driven particle transport from dumping site to nearby soils may be the main reason for metal build-up in the green space soils. Total concentration of Cu showed no significant difference among the soils of the treatments and the control. Although metal accumulation has been occurring in the soils of the Mobarakeh Steel complex green space, total concentrations in the soils were still considerably lower than the allowable levels recommended by the Iranian Environmental Protection Agency.
    Conclusions
    The results of this study revealed that metal accumulation has been occurring in the green space soils of the Mobarakeh Steel complex. Considering the short distance of the dumping and metal smelting sites with the green space and very low concentrations of metals in wastewater, in may be concluded that fall out of metallic particles on the soil surfaces from the dumping and smelting sites is the main route for metals accumulation in the soils of the green space areas.
    Keywords: Available concentration of heavy metals, Industrial wastewater, Total concentration of heavy metals, soil
  • Farid Feizolahpour, Mehdi Kouchakzadeh, Fariborz Abbasi, Mohammad Nabi Gheibi, Rajab Choukan Pages 1584-1594
    Introduction
    Broadcast fertilization method increases fertilizer losses while results in lower nutrient absorption by plant roots. Fertigation is an effective method to increase water and fertilizer efficiency and to reduce the losses of nitrogen. Moreover, it allows farmers to apply the nutrients in splits and few amounts in response to crop needs. In the present study, a field experiment was conducted to investigate the effects of split application of fertilizer in furrow fertigation on nitrogen losses and corn yield.
    Materials And Methods
    Field experiments were carried out factorially in a randomized complete block design with four replicates. Experimental treatments were consisted of three fertilizer splits (two, three, and four splits) and three levels of urea fertilizer (60, 80 and 100% of required urea fertilizer), which compared with the common method (broadcasting fertilizer) as used by farmers in the fields. Experiments were conducted on a one hectare field in 120 meter long and open end furrows. During the crop season, Irrigation water was applied in the same way for all fertigation treatments and the third type of the WSC flumes was used to measure the amount of input and output water in irrigation events. Moreover, for determining the indexes of uniformity of water distribution in carrying out fertigation experiments, the amount of infiltration into the soil was calculated using the Kostiakov-Louis equation. The parameters of this equation were determined using the water volume balance method. Injection of Urea fertilizer was done by using 40-liter barrels were placed at the beginning of Furrows. In this study, the injection of fertilizers was applied in the last 10 to 20 minutes of irrigation time.
    Results And Discussions
    Results showed that water distribution uniformities of low quarter and low half in all tests were very high. Such that the water low quarter distribution uniformities for all treatments were between 90.5 to 98.3 percent and the low half distribution uniformities of water for different treatments were between 94.4 to 99.0 percent. So, according to the high water distribution uniformity and injecting fertilizer in 20-10 minutes at the end of irrigation, it should be stated that the distribution uniformities of fertilizer, used in the experiments, were high too. Statistical analysis showed that nitrogen usage amount and interaction of splits-usage rates of fertilizer had a significant influence on run-off nitrogen losses. The most nitrogen losses were achieved in treatment using 100 percent of fertilization recommendation and there were not significant differences between 60 and 80 percent of fertilization recommendation. It is nothworthy that, in addition to the nitrogen loss by surface runoff, nitrogen deep percolation losses always are also considered. In fertigation treatments, because of high rate of nitrogen injection in short intervals at the end of irrigations, the amount of nitrogen in the surface layer (20-0 cm) was significantly higher than the lower depths and this could led to low percolation losses of nitrogen, but the broadcast fertilization method provided the highest percent of remaining nitrogen in the soil after fertilization, which almost is unusable for plant and in the case of over irrigation or rainfall, the risk of groundwater pollution could be raised. Besides, the results showed that application of nitrogen in 4 splits provided more grain yield compared to the 3 splits level. Also, grain yield of corn increased significantly with increasing nitrogen rate application. The fertigation treatments had better performance of water and fertilizer application efficiencies compared to broadcast fertilization method. The most grain yield was achieved in the fifth treatment by application of 100 percent of fertilization usage recommendation in three splits.
    Conclusion
    In this study, the effect of furrow fertigation on nitrogen losses and corn yield was studied under different splits and amounts of fertilizer consumption. Eventually, fertigation treatments were compared with traditional treatments (fertilizer broadcasting method). According to the obtained results, evaluate the interactions of the effect of split × N usage showed that, the fourth treatment (60% of fertilizer application in 4 splits) can be suggested, owing to its lower N losses by runoff. In addition there were no statistical significant differences of grain yield between the fourth and fifth treatments (100% of fertilizer application in 3 splits). Consequently, it can be concluded that by the usage of 60 percent of the recommended fertilizer application in four equal splits during the growing season, the potential of environmental pollution will be reduced while achieving optimal performance.
    Keywords: Broadcast fertilization, Corn, Fertilizer use efficiency, Run off
  • Ali Reza Kiani, Afshin Mosavat Pages 1595-1606
    Introduction
    Lack of water and deterioration in the quality of soil and water resources are considered to be the prime cause of reduced crop yield in arid and semi-arid regions ‘More crop per drop’ by trickle irrigation, deficit irrigation, and uncommon water are the best strategies for mitigating water crises. Different irrigation management strategies are needed to increase production in different areas. In areas where sufficient water is available, a full irrigation strategy could be a suitable option, while in areas where water is limited, deficit irrigation would be an appropriate method, and finally in areas where water resources are saline, management strategies for achieving sustainable production as well as economic yields would be suitable. Maize is the third most important grain crop in the world following wheat and rice and it is the main source of nutrition for humans and animals. Because of the importance of maize in the world, increasing maize production under environmental stresses is a big challenge for agricultural scientists. Different methods of irrigation and the use of saline water that had satisfactory results for increasing agricultural production have been studied by several investigators . The main objective of this study was to establish an efficient use of limited water resources as well as to explore the possibility of replacing saline water with fresh water using different management techniques.
    Materials And Methods
    A field experiment was conducted over two maize cropping seasons (2012–2013) in northern Iran (Gorgan Agricultural Research Station) to compare different alternate irrigation scenarios using saline water on corn yield, salinity and soil moisture distribution in a randomized complete block design with three replications. Treatments were: T1 and T2 = 100 and 50 % of crop water requirement with non-saline water, respectively; T3 and T4 = variable and fixed full irrigation with saline and non-saline water in every other row, respectively; T5 and T6= fixed and variable deficit irrigation with non-saline water in every other rows, respectively and T7= full irrigation with saline water. To create the desired water salinity (8 dS/m), non-saline well water (1.5 dS/m) and drainage water (20–35 dS/m) were blended in different proportions. A T-tape drip irrigation system (20 m in length) was used in the field experiment.
    Results And Discussion
    In general, corn yield in 2013 was about 1270 kg ha-1 higher than in 2012. From the weather records it can be seen that the second year was drier than the first year. Yield analysis showed that deficit irrigation treatments (T2, T5 & T6) and also alternate salinity treatments (T3 & T4) did not significantly difference. In other words, the deficit irrigation management had no effect on yield. Corn yield in T3 and T4 with 50% of saved fresh water was just reduced to 7 and 1 % of T1, respectively. As a result, comparing treatments T3 and T4 with full irrigation have shown that treatments T3 and T4 are the best option. Comparison of moisture distribution in deficit irrigation treatments showed the highest water content in surface and deep layers was related to the treatments T6 and T2, respectively. The distribution of salinity in the soil profile for treatments T3 and T4 showed that after two years of irrigation with saline water, there is the possibility of use saline water for corn production, but drainage and leaching of soil will need to maintain sustainability.
    Conclusion
    Naturally, in water scarce areas that use some strategic management such as deficit irrigation or saline water use, there is available arable farmland to further develop the irrigated area, and thereby increase total production. According to the results of the two-years where there was a shortage of water to meet crop water requirement and saline water was not available, the use of deficit irrigation managements as described in this study can save fresh water resources and increase total production and farmer's income. If the region is facing a shortage of water resources and saline water is available nearby agricultural land, it is suggested to use alternate furrow irrigation with saline and non-saline water; with the crop water requirement being met by the saline water, the total output will be higher than using deficit irrigation management with non-saline water. Comparision of the distribution of moisture in deficit irrigation treatments showed that surface soil moisture was lower in the treatment of T5 because it was more lateral distribution. In the deeper layers, soil moisture of the treatment T2 was more than others, because it was the predominant infiltration. The two treatments T3 and T4 because of the combined matric and osmotic potential and the movement of water along the sides and deep percolation, resulting widely distributed in soil moisture and thus remaining lower moisture in the soil compare to full irrigation treatments. Consequently, this finding indicates that after two years of corn irrigation using saline (8 dS/m) and non-saline water in every other row (treatments T3 and T4) production can be increased, and in case of proper leaching and drainage management, agricultural sustainability will also preserve.
    Keywords: Deficit Irrigation, Drip irrigation, Salinity
  • Leila Zare, Abdolmajid Ronaghi, Seyed Ali Akbar Moosavi, Reza Ghasemi Pages 1607-1619
    Introduction
    Vermicompost is one of the important bio-fertilizer which is the product of the process of composting different organic wastes such as manures and crop residues using different earthworms. Vermicomposts, especially those are derived from animal wastes,contain the large amounts of nutrients compaired with the composts prepared from crop residues. Vermicomposts contain plant available form of nutrients such as nitrate nitrogen, exchangeable phosphorus and potassium, calcium and magnesium. Nowadays, the use of vermicompost in sustainable agriculture to improve the growth and quality of fruits and crops is very common. Drought occurs when the amount of moisture in soil and water resources and rainfall is less than what plants need for normal growth and function. Two thirds of farm lands in Iran have been located in arid and semi-arid regions with annual rainfall less than150 mm that has been distributed irregularly and unpredictable during growth season imposing water stress in most crops. It indicates the importance of water management and proposing different strategies for mitigating detrimental effect of water stress in croplands. Due to the fact that crops nutrient management under drought and water stress using organic fertilizers is an effective method in reaching to high yields in sustainable agriculture, the objective of the present study was to investigate the influence of vermicompost application on reducing the adverse effects of water stress on the growth and chemical composition of corn in a calcareous soil.
    Materials And Methods
    In order to study the influence of water stress and application of vermicompost on corn dry matter yield and nutrients concentration of corn shoot, a greenhouse factorial experiment (4×3) in completely randomized design with three replications was conducted in college of agriculture, Shiraz university, Shiraz, Iran. The factors consisted of four vermicompost levels (0, 10, 20 and30g kg-1soil equal to 0, 20, 40 and 60 Mg ha-1) and three moisture levels(100, 80and 60%of field capacity(FC)). The soil samples were collected (0-30 cm depth) from a calcareous soil (Fine, mixed, mesic, Typic, Calcixrepts), located at Bajgah, Shiraz, Iran. Soil samples were mixed thoroughly with different levels of vermicompost and transfred to plastic pots. Six corn seeds were planted in each pot and were thinned to three uniform plants, one week after germination. Eight weeks after germination, corn shoots were harvested, dried and recorded. Plant samples were grind using a portable grinder and transferred to the laboratory for chemical analysis. The collected data were statistically analysed using SAS software (9.1.3) package.
    Results And Discussion
    The results indicated that with increasing the levels of vermicompost, dry matter yield and concentrations of total nitrogen (TN), phosphorus (P), iron (Fe), copper(Cu) and zinc (Zn) in corn shoots were significantly increased. But, due to the antagonistic relationship between manganese (Mn) and Zn or Fe,concentrations of Mn were significantly decreased. However, the concentration of Mn was in the sufficiency range. The highest dry matter yield and concentrations of nitrogen and phosphorus in corn shoot was observed at 30 g kg-1 vermicompost treatment, with 19, 10 and 20 % increase (compared to the control), respectively. The application of 30 g kg-1 vermicompost increased the concentrations of Zn, Cu and Fe by 41%, 90% and 75%, respectively and concentration of Mn decreased by 11.88%, compared to the control. Increasing the levels of water stress increased significantly the concentration of nutrients in corn shoot due to the reduction of corn biomass. The highest increase in nutrient concentrations was observed at 60% FC moisture level. Nitrogen and phosphorus concentrations in corn shoots by 12.5and 22.5% and Zn, Cu, Fe and Mn by 25, 83, 43and29% were higher compared to those of control (100% FC), respectively. The interaction effects of water stress and vermicompost on the concentrations of shoot N and Cu were significant and both were incresead by simultanoeus application of vermicompost and levels of water stress. The applicaion of 30 g kg-1 vermicompost (about 60 ton ha-1) under 60% FC moisture level increased significantly dry matter yield and the concentrations of nitrogen, phosphorus, zinc, copper and iron in corn shoot by 29%,5.5%, 23, 110, 41 and 71 percent compared to the control, respectively. However, because of the antagonistic relationships,the iron or manganese concentrations were reduced, but were yet in the sufficiency range. The use of 30 g kg-1 vermicompost under 80% FC moisture level Also increased significantly the concentrations of nitrogen, phosphorus, zinc, iron and copper by 9, 23, 24, 59 and 43 percent compared to the control, respectively.
    Conclusion
    The applicaion of 30 g kg-1 vermicompost increased significantly dry matter yield and the concentration of nitrogen, phosphorus, zinc, copper and iron in corn shoot under water stress treatments. In conclusion, the application of vermicompost mitigated the detrimental effects of water stress on corn dry matter yield and concentration of nutrients due to the positive effects of compost on physical, chemical and biological properties of the calcareous soil.
    Keywords: Corn, Vermicompost, Water stress
  • Mohaddese Savasari, Mostafa Emadi, Mohammad Ali Bahmanyar, Puria Biparva Pages 1620-1633
    Introduction
    Increases in pollution of water resources due to the contaminants have made researchers to develop the various methods in the remediation and the reuses of polluted resources contamination of soils with heavy metals is one of great environmental concerns for the human beings. Cadmium (Cd) as a toxic heavy metal is of significant environmental and occupational concern. Contamination of soils with heavy metals is one of great environmental concerns for the human beings. The numbers of sorbents that have been used for Cd (II) reductive removal are biopolymers, fly ash, activated carbon, metal oxides, clays, zeolites, dried plant parts, microorganisms, and sewage sludge. However, most of the mentioned sorbents had limitations of cost and durability that call a needed approach by cost effective remediation technique with high efficiency. Application of zero valent iron nanoparticles (ZVINs) as a promising technique for remediation of heavy metals are being increasingly considered by researchers. This study was conducted to synthesis and characterize the ZVINs stabilized with ascorbic acid (AAS - ZVIN) in aerobic conditions and to assess their ability for removal efficiency of cadmium (Cd) from the soils and changes in different fraction of Cd in three spiked soils including sandy, acidity and calcareous soils were also studied.
    Materials And Methods
    The stabilized ZVINs were prepared in cold distilled water by reducing Fe (III) to Fe0 using sodium borohydride in the presence of ascorbic acid as stabilizer and reducing agent. The freshly synthesized AAS-ZVIN washed three times and then used for the subsequent analysis. Characterization of the synthesized AAS-ZVIN was carried out by scanning electron microscope (SEM). X-ray diffraction (XRD) was performed using a Philips D500 diffract meter with Ni-filtered Cu ka radiation. To determine the availability of Cd, the DTPA-extractable amounts of Cd in the spiked soils so sandy, acid and calcareous soils with three replications was studied were studied in an experiment of randomized completely design with a factorial arrangement of treatments consisting of AAS-ZVIN dosage (0, 0.5, 1 and 2 w/w %), Cd contamination levels (15 and 45 mg kg-1) in two time periods of 1 and 4 weeks in the three spiked soils. Moreover, the distribution of the chemical forms of Cd was determined using the sequential extraction method.
    Results
    Discussion
    The results of this study show that zero valent iron nanoparticles can be sustained in the future by ascorbic acid under aerobic conditions in a laboratory that is to reduce the cadmium as a useful method, simple, fast and high performance in the decontamination of soils contaminated with lead that require further research to investigate other heavy elements. The results from the obtained SEM and XRD analyses indicated that AAS-ZVINs had the mean size of less than 50 nm, the maximum 2θ peak at 44.8°. Therefore, the particle size of ZVINs produced in this study, measured by SEM images, are less than 100 nm. Chain structure formations have been attributed to the magnetic interactions between the adjacent metal particles. Furthermore, there was an apparent separation between these ZVIN with a little aggregation. Results also showed that the DTPA-extractable Cd in three sandy, acid and calcareous spiked soils decreased with increasing of AAS-ZVIN dosages at both level of contaminations. The availability of Cd in sandy, acid and calcareous spiked soils at 15 and 45 mg kg-1 of contamination were 71 and 49.5 % and 47.52 and 49.47; and 36.05 and 61.3 percentages, respectively. Availability of Cd after four weeks application at two contamination level was also decreased significantly. The results of sequential extraction of sandy, acid and calcareous soils showed that with increasing the level of AAS-ZVIN application from 0 to 2 %, the soluble, exchangeable and carbonate-bound of Cd decreased but organic matter-bound, Fe/Mn oxides bound and residual Cd were increased. Over four weeks after application of AAS-ZVIN in three spiked soils the soluble, exchangeable and carbonate-bound were decreased but organic matter-bound, Fe/Mn oxides bound and residual Cd increased.
    Conclusions
    The results of this study show zero valent iron nanoparticles can be sustained in the future by ascorbic acid under aerobic conditions in a laboratory that is, To reduce the cadmium as a useful method, simple, fast and high performance in the decontamination of soils contaminated with lead that require further research to investigate other heavy elements. Moreover, the high resolution transmission electronmicroscopy, energy dispersive X-ray analysis, x-ray diffraction spectrophotometer measurements are potentially needed to reveal the accurate morphology, composition, crystal structure, functionality and stability of the prepared stabilized-ZVINs. Moreover, these synthesized ZVINs can also possibly applicable for remediation of soils and wastewater.
    Keywords: Extracted with DTPA, Contamination of soil, Sequential extraction
  • Mina Kiyani, Mohammadhassan Salehi, Jahangard Mohammadi, Abdolrahman Mohammadkhani Pages 1634-1645
    Introduction
    The spatial variability of soil properties and its importance in production is a matter-of-debate. Insight about the variability of soil properties as well as the yield of orchards is necessary to achieve higher productivity and better management. Orange is one of the most important export products in our country and to sustainable production of this product, it is necessary to identify the factors affecting its growth. This study was performed to examine the statistical and geo-statistical relationship of some soil properties with the quantitative, qualitative and vegetative properties of Valencia orange in Kazerun area, Fars province.
    Materials And Methods
    The study area contained 1 hectare (Valencia orange crop) of 205-hectare orchards of Rashnabad on the west of Kazerun, Fars province which is 860 meters above the sea level. 120 soil samples were collected from two depths of 0-40 cm and 40-80 cm (according to the root distribution) in order to investigate the statistical and geo-statistical relationship of some soil properties with the properties of Valencia orange. The sampling in the shade and with a minimum distance of one meter from the trunk of the tested tree was performed (It should be noted that orange trees have been planted as row planting with a distance of 5 meters from each other). In addition to the soil samples were collected for statistical studies from the depths 0-40 and 40-80 cm, the combined sampling of two trees that had less distance to the selected points was performed to measure the performance and quality of orange. It should be noted that all the Valencia trees, their age (about eight years) and management approach were similar. Soil samples were then transferred to the laboratory and air dried, the separately packed and passed through 2 mm sieve.Then, different soil and orange properties including soil texture, pH, EC, %OM, %CaCO3, solution potassium and available phosphorous, iron, zinc and manganese, branch length and branch diameter, trunk perimeter, trunk diameter and tree height, total soluble solids, acid percentage, Vitamin C, number of fruits,orange yield,average fruit weight and average fruit size were determined and the data set were analyzed using Statistica 6.0 software.Variograms of the data were drawn using variowin 2.2 and after determining the best fitted model, kriging maps of soil and fruit were prepared using Surfer9 software.
    Results And Discussion
    The results of correlation coefficient showed the significant and positive relationship between organic matter and available manganese of topsoil with total yield and number of fruits. According to the results of fitness of standard models to the empirical exponent change, all the properties had spatial structure. Soil properties including the percentage of clay, the percentage of organic matter, soluble potassium, phosphorous, available zinc and manganese in both depths in the eastern and south-eastern direction of the study area were higher than that of the others. These maps had the same spatial distribution pattern in terms of orange properties including the diameter and length of the current year branch, performance, number of fruits, average fruit size, acid percentage and total soluble solids.
    Conclusion
    The variability coefficient of soil and fruit properties did not show a consistent trend in the study. According to the correlation coefficients, in a few cases, a positive significance correlation was observed as an example, it can be referred to the positive significant correlation of orange yield with the organic matter and manganese in the depth of 0-40 cm. All the studied variables have spatial structure. Among the studied variables, the percentage of organic matter, clay particles percentage, soluble potassium, phosphorous, and available manganese in both depths showed the same spatial distribution pattern as that of the vegetative, qualitative and yield properties of orange including the total performance, fruit number, fruit size, the diameter and length of the current year branch. The proximity of the ranges of soil and fruit properties supports this result and is in line with the results of correlation coefficient. The results also showed that the spatial distribution and pattern of soil and crop variables may be different in a short distance with the same management. The study of the effect of NPK fertilizers on vegetative, qualitative and quantitative properties of orange in the region orchards is recommended. It is also suggested to study the effect of climatic factors on the orange qualitative properties.
    Keywords: Orange quality, Performance, Spatial distribution, Soil variability
  • Setareh Sharifi, Amir Lakzian, Alireza Astaraei, Nasrin Ghorbanzadeh Pages 1646-1661
    Introduction
    Iron cycle is one of the most important biogeochemical processes which affect the availability of iron in soils. Ferric iron oxides are the most abundant forms of iron in soils and sediments. Ferric iron is highly insoluble at circumneutral pH. Present investigations have shown that the structural ferric iron bound in clay minerals is reduced by some microorganisms. Anaerobic bacteria reduce ferric iron which bound to soil clay minerals under anaerobic conditions. They have the ability to use ferric iron as a terminal electron acceptor. Many studies presented that dissimilatory iron reducing bacteria (DIRB) mediate the transfer of electrons from small organic molecules like acetate and glucose to various humic materials (electron shuttles) which then pass electrons abiotically to ferric iron oxyhydroxide and phyllosilicate minerals. Electron shuttles like AQDS, a tricyclic quinone, increase the rate of iron reduction by iron reducing bacteria on sites of iron oxides and oxyhydroxides. By increasing the rate of bioreduction of ferric iron, the solubility and availability of iron enhanced meaningfully. Royer et al. (2002) showed that bioreduction of hematite (common iron mineral in soils) increased more than three times in the presence of AQDS and Shewanella putrefaciens comparedto control treatments. Previous works have mostly used synthetic minerals as electron acceptor in bioreduction process. Furthermore, the effect of quinones as electron acceptor for microorganisms were studied with poorly crystalline ferric iron oxides . The main objective of this study was to study the effect of AQS, humic acid and fulvic acid (as electron shuttle) and Shewanella sp. and Pseudomonas aeruginosa, on bioreduction of native ferric iron in two acidic and calcareous soils.
    Materials And Methods
    An experiment was conducted in a completely randomized design with factorial arrangement and three replications in vitro condition. The soil samples collected from locations in Mashhad and Guilan cities, Iran, in 2015. The soil samples were air dried in a glasshouse and later subjected to general analysis. Some part of the soil samples were kept at 4 oC as fresh soil samples for bioreduction assay. In that part of experiment, all soil samples were treated with glucose (10 mM) as electron donor. Native ferric iron considered as electron acceptor. Then soil samples were treated with AQS, humic acid and fulvic acid (as electron shuttles) and inoculated with bacterial cells (Shewanella sp. and P. aeruginosa) and they were incubated for 30 days in an incubator at 30 and 37 oC according to the optimum temperature for bacteria in an anaerobic condition. At the end of incubation time, ferrous and acid extractable iron were determined with Ferrozine assay by spectrophotometer in 562 nm (8, 25).
    Results And Discussion
    Results showed that the AQS had a noticeable effect on ferrous iron concentrations in both acidic and calcareous soils. In these cases ferrous iron concentrations were 8 and 15.7 times higher compared to initial concentration in acidic and calcareous soils, respectively. The Shewanella sp. intensified ferrous iron concentration 7.2 and 16.3 fold in acidic and calcareous soils, respectively but P. aeruginosa increased it 5.6 and 12.1 fold compared to initial concentration of ferrous iron. In acidic soil, in the presence of Shewanella sp. and AQS, ferrous and acid extractable iron concentrations were 1.45 and 4.50 mg g-1, respectively. Results showed that 11.7 fold enhancements occur in the presence of Shewanella sp. and AQS compared to initial (0.385 mg g-1) concentration of iron in acidic soil. When P. aeruginosa was inoculated in acidic soil in the presence of AQS, soluble ferrous iron concentration was 1.27 mg g-1. The acid extractable iron in this treatment was 2.85 mg g-1. The concentration of soluble ferrous iron in calcareous soil was 0.81 mg g-1, when AQS was added to Shewanella sp. treatments. That value was 0.54 when P. aeruginosa was added. The acid extractable iron was 3.90 mg g-1 in the presence of AQS and Shewanella sp. By adding P. aeruginosa, acid extractable iron was 2.84 mg g-1 compared to control treatments.
    Conclusions
    Dissimilatory ferric iron reduction is a potentially important process in controlling contaminant fate. It has the potential for being particularly useful in the remediation of metals and radionuclides. Means for stimulating ferric iron reduction will be useful in enhancing bioremediation process. Results illustrated that the Shewanella sp. and P. aeruginosa were enhanced the bioreduction of ferric iron in the presence of AQS, humic acid and fulvic acid in soils. When soil samples were inoculated with Shewanella sp., and AQS was added to the soil samples (in acidic and calcareous soil samples) the concentration of ferrous iron increased intensively.
    Keywords: Bioreduction, Dissimilatory Iron Reducing Bacteria, Electron shuttle, Ferric iron
  • Leila Jalali, J. Bazrafshan, A.R. Tavakoli Pages 1661-1672
    Introduction
    There have been several indices for agricultural drought monitoring such as Palmer Drought Severity Index (PDSI), Crop Moisture Index (CMI) and Reconnaissance Drought Index (RDI). These indices model the general conditions of soil moisture as a function of climatic parameters such as temperature and rainfall and they are not appropriate to any specific crop. Crop- Specific Drought Index (CSDI) is among few indices which directly take into account evapotranspiration for drought monitoring. This index is defined based on the ratio of actual evapotranspiration (ETa) to potential evapotranspiration (ETp). Literature review of agricultural drought monitoring in Iran reveals that was mainly used Reconnaissance Drought Index (RDI) and in some cases Drought Severity Index Palmer (PDSI) which have less associated with the growth or performance of the specific crop or not. In this paper, a Crop Specific Drought Index (CSDI) model was evaluated for rain-fed wheat in a cold-temperate climate. Then, it’s correlation with RDI was assessed.
    Materials And Methods
    In this study, using 9 years of data of meteorology, soil, and crop yield and phenology, a CSDI model has been calibrated and validated for rain-fed wheat. A two-layer model of daily soil water balance was used to CSDI calculation. The first layer is the current root growth zone which its depth increases with time. The second layer is between the first layer and maximum depth of root growth which its depth decreases by root growth and the thickness of this layer becomes zero when the root growth is Maximum. Actual daily Evapotranspiration (ETa) was calculated based on two-layer model of daily soil water balance. For this, we used the moisture content of the first layer (active), potential evapotranspiration and daily rainfall values. The statistical indices of error analysis like RMSE, MAE and Index of Agreement was used for assessment of CSDI model. Then, to investigate the correlation possibility of crop specific drought severity, Reconnaissance Drought Index (RDI) was used which is based on two variables of potential evapotranspiration and precipitation. In fact, RDI considers the precipitation as a factor of moisture input and the potential evapotranspiration as a factor of moisture exhaust.
    Results
    Discussion
    At Kermanshah station high coefficient of determination (0.95), relatively high index of agreement (0.747), and low error values (RMSE =0. 098 and MAE =0. 068) was obtained. Sensitivity coefficients during vegetative and productivity stages were obtained 1.31 and -0.0542, respectively. As a result, crop yield at vegetative stage severely affected by aridity stress while at productivity stage there was no sensitivity. In fact, water demand supply is vital at vegetative stage .Range of RDI at Kermanshah station was between 1.13 to -2.59. This threshold is the condition between "moderately wet" and "extreme drought". Correlation between the two index was started from March (R2 =0. 467) and persisted to September (R2 =0. 717). But the highest coefficients of determination were related to July to august (0. 738). Although CSDI didn’t affect by drought stress during October to February, it affected by moisture of March onward. RDI incorporating precipitation and potential evapotranspiration is one of the most recent developments for the assessment of drought severity through drought indices. That is why this index is chosen to investigate the relationship with CSDI. Actually, both indices get evapotranspiration factor in the agricultural drought monitoring. Based on the results, there is a good correlation between two indices. Since the CSDI is relay on ETa to ETp ratio and RDI is based on the P/ ETp ratio, it can be concluded that there is a possible to replacement of ETa with rainfall (R) in the CSDI equation.
    Conclusion
    Many indices and indicators are available to assist in the quantitative assessment of drought severity, and these should be evaluated carefully for their application to each region or location and sector. This paper presents a CSDI model which compared with RDI. Based on the results of this analysis, CSDI model was performed well in high values of coefficients of determination and Index of Agreement, and low values of errors. Therefore, the CSDI seems to be a reliable index to assess agricultural drought. Furthermore, it is observed a reliable relation between CSDI and RDI during crop growth period. Due to good correlation of CSDI and RDI, it can be proposed to replacement of rainfall (R) instead of ETp in the CSDI equation.
    Keywords: Agricultural drought monitoring, Reconnaissance Drought Index, Evapotranspiration, Water balance model
  • Shideh Shams, Seyed Mohammad Moosavi Baigy Pages 1673-1685
    Introduction
    Air temperature as an important climatic factor can influence variability and distribution of other climatic parameters. Therefore, tracking the changes in air temperature is a popular procedure in climate change studies.. According to the national academy in the last decade, global temperature has raised 0.4 to 0.8⁰C. Instrumental records show that, with the exception of 1998, the 10 warmest year (during the last 150 years), occurred since 2000, and 2014 was the warmest year. Investigation of maximum and minimum air temperature temporal trend indicates that these two parameters behave differently over time. It has been shown that the minimum air temperature raises noticeably more than the maximum air temperature, which causes a reduction in the difference of maximum and minimum daily air temperature (daily temperature range, DTR). There are several factors that have an influence on reducing DTR such as: Urban development, farms’ irrigation and desertification. It has been shown that DTR reduction occurs mostly during winter and is less frequent during summer, which shows the season’s effect on the temperature trend. Considering the significant effects of the climatological factors on economic and agricultural management issues, the aim of this study is to investigate daily air temperature range for yearly, seasonal and monthly time scales, using available statistical methods.
    Materials And Methods
    Daily maximum and minimum air temperature records (from 1950 to 2010) were obtained from Mashhad Meteorological Organization. In order to control the quality of daily Tmax and Tmin data, four different types of quality controls were applied. First of all, gross errors were checked. In this step maximum and minimum air temperature data exceeding unlikely air temperature values, were eliminated from data series. Second, data tolerance was checked by searching for periods longer than a certain number of consecutive days with exactly the same temperatures. Third, a revision of internal consistence was done, verifying that daily Tmax always exceeds daily Tmin. Fourth, the temporal coherency was tested by checking if consecutive temperature records differ by more than 8 degrees. The homogeneity of the series was tested by means of the Standard Normal Homogeneity test, the Buishand range and the Pettitt tests, on yearly, seasonal and monthly time scales. Breakpoint can be detected by means of these methods. In addition, Von Neumann ratio test was used to explore the series’ randomness. Having investigated data’s randomness in this study, series’ trend was determined by the Kendal-Tau test. Furthermore, the slope of the series’ trend was calculated using the Sen’s slope method.
    Results
    Discussion
    Results indicated a decreasing trend in DTR during last 60 years (1951-2010) in Mashhad climatological station. Moreover, the results revealed that the slope of yearly DTR was decreasing (-0.029 ⁰C per year), which indicates that minimum air temperature values raise more maximum air temperature values. A breakpoint was detected during 1985. During 1951-1985, the average amount of DTR was 14.6⁰C, while this parameter reduced to 12.9⁰C for the period 1985-2010. The Kendall-Tau test was used to obtain the significance of trend during 1951-2010, 1951-1985 and 1985-2010. The results showed that during 1951-2010, DTR significantly reduced at a rate of 0.29oC per decade. However, between 1951 and 1985, DTR trend increased at a rate of 0.61oC per decade, while DTR trend between 1985 and 2010 reduced at a rate of 0.19 ⁰C per decade, which was not significant (P-value=5%). In the seasonal DTR series, the highest trend’s slope was calculated for the summer data (-0.43 ⁰C in a decade), while the lowest one accrued in spring (-0.15⁰C in a decade). From 1951 to 1985, DTR had an increasing trend, due to minimum air temperature’s downward trend. But from the late 1980 to 2010, as it was expected, downward DTR trend was observed, because during this period minimum air temperature increases more than the maximum air temperature, thus the difference between Tmax and Tmin was reduced. Monthly DTR analysis also revealed a decreasing trend from 1951 to 2010, except for March and April, which had a non-significant increasing trend. In monthly DTR series, as it was expected, similar to the yearly and seasonal time series, the breakpoints accrued around 1985 in 8 out of 12 months. During February, March, April and November no significant breakpoint was detected.
    Conclusion
    DTR decreasing trend indicated that minimum air temperature increase was greater than maximum. This can cause a significant effect on the agricultural sector, hence in an appropriate agricultural management, these points should be considered. For example, changing the sowing time is one of the decisions which a manager can make.
    Keywords: Hemogenety tests, Mashhad, Maximum temperature, Minimum temperature
  • Vesta Afzali, Masoud Reza Hessami Kermani Pages 1686-1699
    Introduction
    The phenomenon of climate change and its consequences is a familiar topic which is associated with natural disasters such as, flooding, hurricane, drought that cause water crisis and irreparable damages. Studying this phenomenon is a serious warning regarding the earth’s weather change for a long period of time.
    Materials And Methods
    In order to understand and survey the impacts of climate change on water resources, Global Circulation Models, GCMs, are used; their main role is analyzing the current climate and projecting the future climate. Climate change scenarios developing from GCMs are the initial source of information to estimate plausible future climate. For transforming coarse resolution outputs of the GCMs into finer resolutions influenced by local variables, there is a need for reliable downscaling techniques in order to analyze climate changes in a region. The classical statistical methods run the model and generate the future climate just with considering the time variable. Multi-site daily rainfall and temperature time series are the primary inputs in most hydrological analyses such as rainfall-runoff modeling. Water resource management is directly influenced by the spatial and temporal variation of rainfall and temperature. Therefore, spatial-temporal modeling of daily rainfall or temperature including climate change effects is required for sustainable planning of water resources.
    Results And Discussion
    For the first time, in this study by ASD model (Automated regression-based Statistical Downscaling tool) developed by M. Hessami et al., multi-site downscaling of temperature and precipitation was done with CGCM3.1A2 outputs and two synoptic stations (Rasht and Bandar Anzali) simultaneously by considering the correlations of multiple sites. The model can process conditionally on the occurrence of precipitation or unconditionally for temperature. Hence, the modeling of daily precipitation involves two steps: one step, precipitation occurrence and the other step precipitation amounts and the modeling of daily temperature is performed in one step. The choice of predictor variables is one of the most influential steps in the development of statistical downscaling scheme because the decision largely determines the character of the downscaling results. It is essential to remember that predictors relevant to the local predict and should be adequately reproduced by the host climate model at the spatial scales used to condition the downscaled response. To test this approach over the current period and to compare the results with observed data, temperature and precipitation, from 2 stations, model is evaluated and calibrated by using NCEP (National Center for Environmental Prediction) reanalysis data before the use of GCMs as input variables. Then climate was predicted for three periods which each period consist of thirty years in the future, 2011-2040, 2041-2070 and 2071-2100. ASD reduces the problem of predictor selection and it is capable of performing all steps of statistical downscaling automatically. In order to select dominant predictors in multi-site modeling backward stepwise regression method was used; so that some predictors like 850 hPa geopotential, 850 hPa specific humidity, 1000 hPa specific humidity, screen air temperature (2m) were the most important variables for temperature models, and 850 hPa geopotential, 1000 hPa zonal velocity, 1000 hpa specific humidity, and screen air temperature (2m) played a main role in temperature modeling. For downscaling of precipitation, the amount of explained variance (R2) is 0.336 for NCEP data and it is 0.89, 0.922 and 0.855for maximum, mean and minimum temperature, respectively. The results underlined certain limitations to downscale the precipitation regime and its strength compared to downscale the temperature regime. To evaluate the performance of the multi-site statistical downscaling approach, several climatic and statistical indices were developed. For instance, based on daily total precipitation, two precipitation indices was used including percentage of wet days, maximum number of consecutive dry days. The results showed the increase of the average temperature and precipitation decreases for future mainly. In this case study, the decrease of 0.30 mm day-1 in the average rainfall on the second period of future, 2041-2070, and the reduction of 7.25% on the 3rd period, 2071-2100, in climate index of the percentage of wet days was predicted, compared to the based period. However, the results illustrated an increase in the mean of maximum, mean, and minimum temperature, 3.17, 2.5 and 2.8 °C, for the 3rd period of future from 2071 to 2100, respectively.
    Conclusions
    The aim of applying this new method is to demonstrate the importance of multi-site models and developing a suitable context to calculate the uncertainty of climate predictions. Further works are needed to evaluate in depth the fundamental assumption of multi- site statistical downscaling, i.e. the stability of the relationships between predictors and predict and in altered climate and test their plausibility and consistency.
    Keywords: ASD model, General Circulation Models, Predictand, Predictor
  • Mohammad Ghabaei S., Hamid Zare Abyaneh, Abolfazl Mosaedi, S. Zahra Samadi Pages 1700-1717
    Introduction
    Drought is a recurrent feature of climate that caused by deficiency of precipitation over time. Due to the rise in water demand and alarming climate change, recent year’s observer much focus on drought and drought conditions. A multiple types of deficits and relevant temporal scales can be achieved through the construction of a joint indicator that draws on information from multiple sources and will therefore enable better assessment of drought characteristics including return period, persistent and severity. The Standardized Precipitation Evapotranspiration Index (SPEI) combines information from precipitation and temperature in the form of water surplus or deficit according to Standardized Precipitation Index (SPI). Rainfall over some regions of Iran during some resent year was below average while mean and maximum temperatures were very high during this period, as was evaporation. This would suggest that drought conditions were worse than in previous recent periods with similarly low rainfall. The main objective of this study is to assess the influences of humidity on the SPEI index and investigate its relation with SPI and Reconnaissance Drought Index (RDI) over six different climatic regions in Iran.
    Materials And Methods
    Iran has different climatic conditions which vary from desert in central part to costal wet near the Caspian Sea. In this study the selection of stations was done based on Alijani et al (2008) climatic classification. We chose 11 synoptic stations from six different climatic classes including costal wet (Rasht and Babolsar), semi mountains (Mashhad and Tabriz), mountains (Shiraz and Khoram Abad), semi-arid (Tehran and Semnan), arid (Kerman and Yazd) and costal desert (Bandar Abas). The Meteorological datasets for the aforementioned stations were obtained from the Iran Meteorological Organization (IRIMO) for the period 1960-2010. The compiled data included average monthly values of precipitation, minimum and maximum air temperature, mean relative humidity, sunshine hours) and wind speed at 2 m height. A probability-based overall water deficit assessment was achieved from multiple drought-related indices (i.e. SPEI, SPI and RDI). The humidity conditions were monitored for given stations based on each index during annual, short term (1, 3 and 6 months) and long term (9 , 12, 18 and 24 months) periods. This research further examine the Locally Weighted Scatter plot Smoothing (LOWESS) graphical method and nonparametric Man- Kendal test to evaluate the trends associated with humidity deficiency in annual and monthly time scales during 51 years period (i.e. 1960-2010).
    Results And Discussion
    Our results revealed that the maximum correlation between SPEI index with indices of SPI and RDI was achieved in the coastal wet region and with a declining trend in relative humidity condition in the rest of the regions, this correlation is down over both short- and long-term periods. A comparison between SPI and SPEI also performed that the SPI index was able to reflect prolonged drought over the costal wet region where it showed significant inconstancy in desert and semi desert regions. SPEI result suggested substantial deficiencies in relative humidity at the beginning of 1997 during long term period which indicated an increasing trend of drought statues during last decades. Overall, according to the results of SPEI index in 1month periods monthly drought assessment showed a declining trend in drought magnitude during autumn, winter and spring season months (October to June) at investigated stations excepts Tehran and Shiraz stations and with a potential deficiency in relative humidity conditions. Unlikely, annual trend showed increasing trends in drought frequency and persistent over last decade.
    Conclusion
    Our results can be summarized as below:Focusing on various types of deficits, the result of humidity based deficiencies indicated that for semi-mountains, mountains, semi-arid, arid and costal desert regions the period of 1997 to 2010 has a large total moisture shortage over all climatic regions. Most of the climate stations showed moisture deficits (decline trends) during October to June (9-month) at many stations expect Tehran and Shiraz stations which revealed a significant increasing over 51 years. We recommend using SPEI index for arid and semi-arid regions because it includes temperature variability in drought model so it reflects drought conditions better than other indices. Furthermore, three drought indices (i.e. SPEI, SPI and RDI) have similar sensitivity to water deficits over wet climatic regions; therefore, each of those indices can be used.
    Keywords: Drought, LOWESS Graphical Technique, Man-Kendal Test, Water Surplus or Deficit
  • Amirhosein Aghakhani Afshar, Yousef Hassanzadeh, Ali Asghar Besalatpour, Mohsen Pourreza Bilondi Pages 1718-1732
    Introduction
    Hydrology cycle of river basins and water resources availability in arid and semi-arid regions are highly affected by climate changes, so that recently the increase of temperature due to the increase of greenhouse gases have led to anomaly in the Earth’ climate system. At present, General Circulation Models (GCMs) are the most frequently used models for projection of different climatic change scenarios. Up to now, IPCC has released four different versions of GCM models, including First Assessment Report models (FAR) in 1990, Second Assessment Report models (SAR) in 1996, Third Assessment Report models (TAR) in 2001 and Fourth Assessment Report models (AR4) in 2007. In 2011, new generation of GCM, known as phase five of the Coupled Model Intercomparison Project (CMIP5) released which it has been actively participated in the preparation of Intergovernmental Panel on Climate Change (IPCC) fifth Assessment report (AR5). A set of experiments such as simulations of 20th and projections of 21st century climate under the new emission scenarios (so called Representative Concentration Pathways (RCPs)) are included in CMIP5. Iran is a country that located in arid and semi-arid climates mostly characterized by low rainfall and high temperature. Anomalies in precipitation and temperature in Iran play a significant role in this agricultural and quickly developing country. Growing population, extensive urbanization and rapid economic development shows that Iran faces intensive challenges in available water resources at present and especially in the future. The first purpose of this study is to analyze the seasonal trends of future climate components over the Kashafrood Watershed Basin (KWB) located in the northeastern part of Iran and in the Khorsan-e Razavi province using fifth report of Intergovernmental Panel on climate change (IPCC) under new emission scenarios with Mann-Kendall (MK) test. Mann-Kendall is one of the most commonly used nonparametric tests to detect climatic changes in time series and trend analysis. The second purpose of this study is to compare CMIP5 models with each other and determine the changes in rainfall and temperature in the future periods in compare with base period on seasonal scale in all parts of this basin.
    Materials And Methods
    In this research, keeping in view the importance of precipitation and temperature parameters, fourteen models obtained from the General Circulation Models (GCMs) of the newest generation in the Coupled Model Intercomparison Project Phase 5 (CMIP5) were used to forecast the future climate changes in the study area. In historical time (1992-2005), simulated data of these models were compared with observed data (34 rainfall and 12 temperature stations) using four evaluation criteria for goodness-of-fit including Nash-Sutcliffe (NS), Percent of Bias (PBIAS), coefficient of determination (R2) and the ratio of the root mean square error to the standard deviation of measured data (RSR). Furthermore, all models have a very good rating performance for all of the evaluation criteria and therefore investigation is done for precipitation data as an important component in survey of climate subject to select the optimum models in kashafrood watershed basin.
    Results And Discussion
    By comparing four evaluation criteria for fourteen models of CMIP5 during historical time, finally, four climate models, including GFDL-ESM2G, IPSL-CM5A-MR, MIROC-ESM and NorESM1-M which indicated more agreement with observed data according to the evaluation criteria were selected. Furthermore, four Representative Concentration Pathways (RCPs) of new emission scenario, namely RCP2.6, RCP4.5, RCP6.0 and RCP8.5 were extracted, interpolated and then under three future periods, including near-century (2006-2037), mid-century (2037-2070) and late-century (2070-2100) were investigated and compered.
    Conclusions
    The results of Mann-Kendall test which was applied to examine the trend, revealed that the precipitation have variable positive and negative trends which were statistically significant. In addition, mean temperature have a significant positive trend with 90, 99 and 99.9% confidence level. In seasonal scale, survey of climatic variable (rainfall and mean temperature) showed that the maximum and minimum of precipitations occur during spring and summer and mean temperature in all seasons is higher than historical baseline, respectively. Maximum and minimum of mean temperature occur in summer and winter, and the amount of seasonal precipitation in these seasons will be reduced. Finally, across all parts of kashafrood watershed basin, rainfall and mean temperature will be reduced and increased, respectively. In conclusion, models of CMIP5 can simulate the future climate change in this region and four models of CMIP5 can be used for this region.
    Keywords: Climate change, Fifth assessment report, Greenhouse gases, RCP scenario, Mann-Kendall test