فهرست مطالب

  • سال سی و سوم شماره 3 (شهریور 1398)
  • تاریخ انتشار: 1398/08/12
  • تعداد عناوین: 10
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  • رضا مزارعی، عبدعلی ناصری، امیر سلطانی صفحات 379-389

    یکی از مهم‌ترین پارامترها در طراحی یک سیستم آبیاری، تعیین پارامتر نفوذ است که می‌تواند منجر به افزایش عملکرد یک سیستم آبیاری شود. در این تحقیق، پارامترهای نفوذ معادله کوستیاکف-لوئیس با دو دسته از روش‌های مختلف از جمله روش مستقیم (روش‌های دونقطه‌ای الیوت-واکر و ورودی- خروجی) و مدل‌های کامپیوتری (مدل کامپیوتری SIPAR_ID و IPARM) تعیین گردید و با نتایج به‌دست‌آمده از آزمایش‌های مزرعه‌ای مورد مقایسه قرار گرفت. مطالعات مزرعه‌ای به‌منظور جمع‌آوری داده‌های مورد نیاز، در مزارع تحت کشت نیشکر سلمان فارسی در تابستان و پائیز سال 1396 در نه جویچه به طول 100 و عرض 1/83 متر و شیب 0/04 درصد تحت سه دبی اسمی 1، 1/5 و 2 لیتر بر ثانیه در سه نوبت آبیاری صورت گرفت. در این تحقیق به‌منظور ارزیابی دقت تخمین پارامترهای نفوذ از سه شاخص حجم آب نفوذ یافته به منطقه ریشه، زمان پیشروی و حجم رواناب استفاده گردید. جهت شبیه‌سازی شاخص‌های ارزیابی در هر روش، از نرم‌افزار WinSRFR استفاده گردید. مطابق نتایج این تحقیق، روش مستقیم دونقطه‌ای الیوت-واکر در تخمین زمان پیشروی با میانگین RMSE، MAE و RE به ترتیب 52/10، 14/91و 10/1 درصد، حجم آب نفوذ یافته به ترتیب با میانگین 9/6، 7/36 و 7/8 درصد، حجم رواناب خروجی به ترتیب با میانگین 8/8، 8/7 و 1/2 درصد، از عملکرد بسیار قابل قبولی برخوردار بود. همچنین دیگر روش مستقیم (روش ورودی-خروجی) به ترتیب با میانگین 11/4 و 6/8درصد برای حجم آب نفوذ یافته و 1/6 و 0/3 درصد برای حجم رواناب مقدار شاخص‌های آماری RMSE و RE را تخمین زد که نشان از دقت بالای این روش در تخمین این دو شاخص عملکرد بود، هرچند که این روش با میانگین 11/25 و 2/27 درصد توانایی شبیه‌سازی زمان پیشروی را با دقت مناسب نداشت. از سوی دیگر نتایج مدل‌های کامپیوتری نشان داد که مدل IPARM با میانگین MAE و RE برابر با 23/38، 15/5 درصد زمان پیشروی، 20/02 و 26/7 درصد حجم آب نفوذ یافته و 11/81 و 1/8 درصد حجم رواناب را تخمین زد، که در مقایسه مدل SIPAR_ID از عملکرد بهتری برخوردار بود. در حالت کلی هرچند که مدل‌های کامپیوتری در تخمین پارامترهای نفوذ از عملکرد قابل قبولی برخوردار بودند اما روش‌های مستقیم به دلیل استفاده از داده های ورودی بیشتر و استفاده از داده های تمامی مراحل آبیاری از عملکرد بهتری برخوردار بودند.

    کلیدواژگان: پارامتر نفوذ، روش دونقطه ای، روش ورودی-خروجی، SIPAR، ID، IPARM
  • حسین دهقانی *، حمیدرضا حاجی، علی اصغر قائمی صفحات 391-404

    شناخت تغییرات جبهه رطوبتی خاک یک شاخص مهم در مدیریت و طراحی سامانه آبیاری قطره ای زیر سطحی می باشد. پژوهش حاضر با هدف بررسی تغییرات جبهه ی رطوبتی خاک برای رژیم های مختلف آبیاری در یک سامانه آبیاری قطره ای زیرسطحی در باغ پسته، در یک خاک لوم شنی در منطقه‌ ی صفائیه، از توابع شهرستان سرخه در استان سمنان انجام شد. تیمارهای پژوهش شامل سه رژیم آبیاری منطبق بر مدیریت زارع (I1)، نیاز آبی (I2) و نیاز آبی و آبشویی (I3) بود و تغییرات جبهه ی رطوبتی در عمق های مختلف خاک در زمان قبل و بعد از آبیاری و در مراحل مختلف رشد بررسی شد. در سامانه آبیاری مورد مطالعه افزایش سطوح رژیم آبیاری منجر به افزایش میزان رطوبت در محیط ریشه شد و بیشترین مقدار برابر با 6/16 درصد در رژیم آبیاری I3 و در زمان بعد از آبیاری مشاهده شد. در رژیم آبیاری I1 میزان آب آبیاری به اندازه ای بود که حرکت رطوبت به سمت بالای قطره‌چکان ها در قبل و بعد از آبیاری اختلاف معنی داری نداشت. نتایج نشان داد که رطوبت در عمق 75 سانتی متری خاک نسبت به عمق 25 و 50 سانتی متر دارای افزایش معنی داری بود که به تجمع بیشتر ریشه های مصرف کننده آب در عمق 50-0 سانتی متری نسبت داده شد. رژیم آبیاری I3 و عمق 75 سانتی متری با مقدار 19/3درصد بیشترین مقدار رطوبت را دارا بود که موجبات نفوذ عمقی را نیز فراهم می کند. بالاترین مقدار رطوبت (22/5درصد) در رژیم آبیاری I3 و در عمق 75 سانتی متر و بعد از آبیاری و کم ترین مقدار رطوبت (10/5درصد) در رژیم آبیاری I1 در عمق 25 سانتی متر و قبل از آبیاری نشان داده شد.

    کلیدواژگان: جبهه رطوبتی، زمان آبیاری، عمق خاک، قطره ای زیر سطحی، نیاز آبشویی
  • رسول زمانی *، احسان فتحی، سمیرا بیاتی، پونه قربانی صفحات 405-417

    رودخانه یک اکوسیستم پویا است که علاوه بر اهمیتی که در صنعت، کشاورزی و شرب دارد، تحت تاثیر فعالیت‌های مختلف قرار می‌گیرد. هدف از این مطالعه ارزیابی کیفیت آب رودخانه بهشت‌آباد واقع در استان چهارمحال و بختیاری با استفاده از شاخص آلودگی Liou و انتخاب مهم‌ترین پارامترها بر اساس تجزیه و تحلیل مولفه اصلی می‌باشد. در این مطالعه 7 پارامتر کیفی آب شامل دما، اکسیژن محلول، اکسیژن خواهی بیولوژیکی، نیتروژن آمونیاکی، هدایت الکتریکی، کل مواد جامد معلق و پتانسیل هیدروژن در طول رودخانه در 7 ایستگاه انتخابی به مدت شش ماه از فروردین‌ تا شهریور سال 1395 با استفاده از روش های استاندارد سنجش آب و فاضلاب مورد اندازه‌گیری قرار گرفتند. یافته های حاصل از مطالعه حاضر نشان داد که کیفیت آب طی مدت پژوهش در ایستگاه‌های نمونه‌برداری و در تمامی ماه‌ها طبق شاخص آلودگی Liou در طبقه کیفیت خوب بوده ‌است. همچنین طبق تکنیک آماری تحلیل مولفه اصلی دو مولفه به‌عنوان مولفه اصلی معرفی شدند. نتایج تحقیق نشان داد که پارامترهای اکسیژن خواهی بیولوژیکی، هدایت الکتریکی، کل مواد جامد معلق در بعضی از ایستگاه‌ها در محدوده استاندارد و در برخی دیگر بیش از حد استاندارد بودند. علاوه بر این نتایج مطالعه نشان داد که کیفیت آب رودخانه بهشت‌آباد در طی ماه‌های مختلف تغییرات چندانی نداشت و کیفیت آب خوب بود. این پژوهش، سودمندی و کارایی تکنیک آماری چند متغیره تحلیل مولفه اصلی و استفاده از شاخص ها را به منظور مدیریت موثر کیفیت آب سطحی نشان می‌دهد.

    کلیدواژگان: استان چهارمحال و بختیاری، پارامترهای فیزیکوشیمیایی آب، شاخص آلودگی رودخانه، منابع آب
  • محمدرضا دلالیان*، فاطمه ذبیحی، انورالسادات پاک نژاد، مینا خوش خوان صفحات 417-430

    یکی از راهکارهای اصلی بهبود شرایط فیزیکی خاک های تحت کشت، اضافه کردن اصلاح کننده های آلی و معدنی به خاک می باشد. این تحقیق با هدف بررسی تاثیر سه نوع ماده اصلاحی شامل هومات پتاسیم، پرمرغ و ورمی کمپوست با درصدهای وزنی متفاوت بر روی خصوصیات فیزیکی خاک و در سطوح مختلف رطوبتی در شرایط مزرعه (تحت کشت گندم) اجراء گردید. طرح به صورت فاکتوریل در قالب طرح پایه بلوک های کامل تصادفی در سه تکرار انجام شد. مواد اصلاح کننده به طور یکنواخت تا عمق 10 سانتی متری با خاک مخلوط و تیمارهای رطوبتی اعمال شد. قبل و بعد از آزمایش از کرت ها نمونه برداری به عمل آمد. پارامترهای فیزیکی شامل: جرم مخصوص ظاهری (Bd)، رطوبت های ظرفیت مزرعه ای (FC) و نقطه پژمردگی دائم (PWP)، پایداری خاکدانه های مرطوب (WAS)، هدایت هیدرولیکی اشباع (KS)، مقاومت فروروی (PR)، شیب منحنی رطوبتی در نقطه عطف (Si)، میانگین وزنی قطر خاکدانه ها (MWD) و بعد فراکتالی جرمی خاکدانه ها (Dm) محاسبه گردید. نتایج نشان داد مصرف مواد آلی موجب کاهش Bd (89%) و افزایش FC ،PWP (87% و 91%) Ks و WAS (3/7 و 2/5 برابر) می گردد. با افزایش سطوح رطوبتی و مقدار ماده آلی بخصوص هومات پتاسیم، میزان Si کاهش یافت (101%). PR با افزایش سطوح رطوبتی کاهش یافت. بر خلاف انتظار با افزایش میزان ماده آلی،Dm و MWD کاهش یافت. مواد آلی در زمان های طولانی تر و در رطوبت های بالا موجب بهبود پایداری خاکدانه ها می گردد. با توجه به تاثیر مثبت مواد آلی بر بسیاری از پارامترهای فیزیکی خاک، این مواد بخصوص پرمرغ بعلت ارزان‌تر و دردسترس بودن، برای اصلاح خاک ها پیشنهاد می گردد.

    کلیدواژگان: پایداری خاکدانه ها، رطوبت خاک، ساختمان خاک، کودهای آلی، مواد اصلاح کننده
  • سمیرا سالاری، پژمان طهماسبی، فرزانه نیکوخواه، مهدی پژوهش* صفحات 431-443

    اگرچه مطالعات زیادی در خصوص اثر رهاسازی اراضی کشاورزی انجام گرفته است ولی اطلاعات بسیار کمی در خصوص تاثیر شرایط آب و هوایی بر احیاء زمین‌های کشاورزی بعد از رهاسازی آن‌ها وجود دارد. به همین منظور در این مطالعه اثر متقابل رهاسازی اراضی کشاورزی و شرایط اقلیمی بر ذخایر ماده آلی ذرات اولیه خاک مورد بررسی قرار گرفت. نمونه‌های مرکب خاک از عمق 30-0 سانتی‌متری در سه تکرار از دو منطقه با شرایط بارندگی متفاوت شامل مناطق حفاظت‌شده شیدا و خرگوش در استان چهارمحال و بختیاری از چهار کاربری مرتع، اراضی کشاورزی و اراضی رها شده زراعی در توالی زمانی 15-10 و 40-15 سال، تهیه و میزان توزیع کربن و نیتروژن در اجزای مختلف ذرات اولیه خاک تعیین گردید. نتایج نشان داد که کشت و کار در اراضی بکر بسته به موقعیت اقلیمی می‌تواند اثرات مثبت و منفی بر اکوسیستم‌های طبیعی داشته باشد. به تبع در منطقه شیدا با وجود میزان بارندگی و وضعیت خوب پوشش طبیعی مراتع کشت و کار در اراضی بکر اثرات منفی در جهت کاهش ماده آلی داشته است. در حالی که در منطقه خرگوش با وجود میزان بارندگی اندک و کیفیت پایین مراتع، کشت و کار اثرات سوء ای نداشته است. در کلیه کاربری‌های مدیریتی مقدار کربن و نیتروژن به ترتیب در ذرات رس، سیلت و شن بیشتر بود. رهاسازی اراضی کشاورزی و مراتع در منطقه خرگوش تاثیری بر غلظت کربن و نیتروژن سه جزء شن، سیلت و رس نداشت اما در منطقه شیدا افزایش زمان رهاسازی کربن اجزای شن و سیلت را افزایش داد ولی تاثیری بر کربن جزء رس نداشت. نتایج نشان داد رهاسازی اراضی کشاورزی بسته به شرایط آب‌و‌هوایی هر منطقه جهت استقرار مجدد پوشش گیاهی و افزایش ترسیب کربن خاک می‌تواند اثرات متفاوت و بالقوه‌ای بر احیای کربن مراتع داشته باشد.

    کلیدواژگان: ذرات اولیه خاک، رهاسازی اراضی کشاورزی، کربن آلی و نیتروژن کل، مراتع بدون کشت و کار
  • اکبر کریمی، مصطفی چرم، عبدالامیر معزی*، نعیمه عنایتی صفحات 445-461

    هدف از این پژوهش بررسی تاثیر کاربرد زغال های زیستی تهیه شده از باگاس نیشکر در دماهای مختلف بر تغییرات شکل های شیمیایی روی در یک خاک آهکی بود. به این منظور زغال های زیستی تهیه شده در دماهای 200 (B200)، 350 (B350) و 500 (B500) درجه سلسیوس در سطوح 1 و 2 درصد وزنی با نمونه خاک ترکیب شدند. نمونه ها به مدت سه ماه در شرایط انکوباسیون و در دمای ثابت نگهداری شدند. در پایان آزمایش از خاک های تیمار شده نمونه برداری شد و برخی ویژگی های شیمیایی خاک و شکل های شیمیایی روی در خاک اندازه گیری شدند. نتایج نشان داد کاربرد هر سه نوع زغال زیستی سبب افزایش ظرفیت تبادل کاتیونی و کربن آلی خاک شد. pH خاک در تیمارهای B200 کاهش یافت، اما در تیمارهای B350 و B500 افزایش یافت. غلظت شکل تبادلی روی در خاک تیمار شده با زغال های زیستی B350، B500 به ترتیب 5/2 و 14/2درصد کاهش یافت، اما در تیمار B200، 17/0درصد افزایش یافت. کاربرد هر یک از زغال های زیستی B200، B350 و B500 سبب افزایش شکل های کربناتی (به ترتیب 4/5، 13/2و 23/3درصد) و آلی (به ترتیب 83/3، 6/3 و 9/2 درصد) روی در خاک شد. کم ترین غلظت شکل باقی مانده روی مربوط به خاک تیمار شده با زغال زیستی B200 بود. نتایج همچنین نشان داد که بیش ترین تغییرات شکل های شیمیایی روی در خاک مربوط به سطح کاربرد 2 درصد زغال های زیستی بود. به طور کلی می توان نتیجه گیری کرد کاربرد زغال زیستی تهیه شده از باگاس نیشکر در دمای گرماکافت 200 درجه سلسیوس (به ویژه در سطح 2 درصد وزنی) می تواند با کاهش شکل باقی مانده روی و افزایش شکل های با فراهمی نسبتا بیش تر از جمله شکل تبادلی، در بهبود فراهمی روی در خاک های آهکی موثر باشد.

    کلیدواژگان: اصلاح کننده های آلی، دمای گرماکافت، عصاره گیری دنباله ای، فراهمی روی
  • حمید زارع، فرزانه حیدری، غلام رضا حیدری، مهدی جوزی* صفحات 463-476

    در این پژوهش گلدانی، اثر سه سطح صفر (A0)، سه (A1) و پنج گرم (A2) سوپرجاذب اکوازورب در هر کیلوگرم خاک، سه سطح 70 (W1)، 85 (W2) و 100 (W3) درصد نیاز آبیاری و دو سطح 75 (F1) و 100 (F2) درصد نیاز کود نیتروژنی بر برخی صفات گیاه فلفل دلمه بررسی شد. آزمایش به‌صورت فاکتوریل در قالب طرح بلوک‌های کامل تصادفی در 18 تیمار و سه تکرار انجام یافت. نتایج بیان‌گر معنی‌داری اثر تیمارهای سوپرجاذب و آبیاری بر تمامی مولفه‌ها به‌جز قطر ساقه بود. در بین تیمارهای سوپرجاذب، بیشترین مقادیر عملکرد میوه با 666/2گرم و بهره‌وری آب 12/36کیلوگرم بر مترمکعب در تیمار A2 به‌دست آمد. در بین تیمارهای آبیاری نیز بیشترین مقادیر عملکردهای ذکر شده به‌ترتیب با 81/621 گرم در تیمار W3 و 10/57کیلوگرم بر مترمکعب در تیمار W1 به‌دست آمد. اثر تیمارهای کودی نیز بر وزن اندام هوایی، ریشه و عملکرد میوه معنی‌دار شد. بیشترین عملکرد میوه به مقدار 638/70گرم در تیمار F2 به‌دست آمد. اثر متقابل دو متغیر آب با سوپرجاذب نیز با تاثیر بر مولفه‌های وزن تر و خشک اندام هوایی و زیرزمینی و بر عملکرد و بهره‌وری آب، سبب حصول بیشترین مقادیر عملکرد میوه (916/65گرم) و بهره‌وری (14/55کیلوگرم بر مترمکعب) در تیمار A2W3 شد. اثرات متقابل سوپرجاذب و کود نشان دادکه بیشترین مقدار عملکرد و بهره‌وری آب معادل 670/51گرم و 12/44کیلوگرم بر مترمکعب در تیمار A2F2 به‌دست آمد. اثرات متقابل آب و کود نیز نشان دادکه بیشترین مقدار عملکرد و بهره‌وری آب معادل 625/59گرم در تیمار W3F2 و 12/32کیلوگرم بر مترمکعب در تیمار W1F2 به‌دست آمد. اثر متقابل سه متغیر سوپرجاذب، آب و کود بر کلیه صفات مورد بررسی غیرمعنی‌دار شد.

    کلیدواژگان: اندام هوایی، ریشه، عملکرد میوه، گلخانه
  • مهدی رحمتی، ایرج اسکندری، مهدی کوسه لو*، ولی فیضی صفحات 477-478

    به‌منظور مطالعه اثرات خاک‌ورزی سنتی و حفاظتی بر خصوصیات فیزیکی خاک در اراضی کشاورزی دیم، تحقیقی به مدت 5 سال زراعی در موسسه تحقیقات دیم کشور در قالب طرح بلوک‌های کامل تصادفی با 5 تیمار خاک‌ورزی شامل: کاشت مستقیم در ته ساقه‌ها (NT1)، کاشت مستقیم در کلیه بقایا (NT2)، شخم قلمی + دیسک (CH)، کم خاک‌ورزی (MT) و شخم مرسوم (CT) در 4 تکرار به اجرا در آمد. نمونه‌برداری‌های خاک در انتهای سال پنجم برداشته شدند که این نمونه جهت آنالیز پارامترهای فیزیکی ازجمله پایداری خاکدانه‌ها (WAS)، میانگین وزنی و هندسی قطر خاکدانه ها به روش الک تر (GMDwet و MWDwet) و الک خشک (GMDdry و MWDdry)، بعد فرکتال جرمی خاکدانه‌ها (Dm)، کربن آلی کل (TOC)، کربن آلی محلول (DOC) و جرم مخصوص ظاهری خاک استفاده شدند. نتایج نشان داد که اثر تیمارهای خاک‌ورزی بر پارامترهای MWDdry و GMDdry معنی‌دار بود. اثر متقابل روش‌های مختلف خاک‌ورزی و مکان بر روی DOC و اثر متقابل عمق و مکان بر روی جرم مخصوص ظاهری معنی‌دار بود. میزان کربن آلی محلول در تیمار خاک‌ورزی سنتی با مقدار mg g-1 74/3 در مکان اول به‌طور معنی‌داری بیشتر از سایر تیمارها (با مقادیر کمتر از mg g-1 3/20) بود. همچنین در تیمار NT1 و NT2 میانگین وزنی (به ترتیب با 1/25 و 1/17 میلی متر) و هندسی (1/04 میلی متر برای هر دو) قطر خاکدانه ها اختلاف معنی‌داری با سایر تیمارها داشت. بر اساس نتایج به‌دست‌آمده توصیه می‌شود، به‌جای استفاده مداوم از خاک‌ورزی سنتی از خاک‌ورزی حفاظتی استفاده شود.

    کلیدواژگان: بعد فرکتال، پایداری خاکدانه ها، جرم مخصوص ظاهری، کربن آلی محلول
  • ابراهیم سپهر، عباس صمدی، محسن برین، بهنام دولتی، میرحسن رسولی، رحمت الله رنجبر* صفحات 489-500

    برخی از ریزجانداران خاک توانایی انحلال کانی‌های حاوی پتاسیم و آزادسازی پتاسیم آن را دارند. این مطالعه به منظور جداسازی باکتری‌های حل‌کننده کانی‌های پتاسیم‌دار (KSBs) از خاک ریزوسفر توتون و بررسی تاثیر آنها بر آزادسازی پتاسیم از خاک‌ انجام شد. نمونه‌‌های خاک از ریزوسفر توتون رقم بارلی21 در مرحله گلدهی بوته برداشت شد. با استفاده از محیط‌کشت جامد الکساندروف، 9 جدایه‌ KSB جداسازی و خالص‌سازی شدند. سپس ارزیابی‌های کیفی (شاخص حلالیت) و کمی (آزادسازی پتاسیم از کانی‌های پتاسیم‌دار) به ترتیب در محیط‌کشت جامد و مایع الکساندروف و بررسی تاثیر جدایه‌های KSBs بر مقدار پتاسیم قابل استفاده خاک در قالب 3 طرح کاملا تصادفی با 3 تکرار صورت گرفت. بیشترین شاخص حلالیت در اثر فعالیت جدایه‌های باکتری KSB22، KSB42 و KSB10 در محیط‌کشت جامد الکساندروف به ترتیب 82، 2/7 و 2/5 به دست آمد و بیشترین میزان پتاسیم محیط‌کشت مایع الکساندروف با مقدار 9/40 میلی‌گرم بر لیتر مربوط به تلقیح جدایه‌های باکتری KSB42 و KSB10 بود که میزان آن نسبت به شاهد (محیط‌کشت بدون تلقیح)، سه برابر افزایش یافت. جدایه‌های KSB42 و KSB10 در آزادسازی پتاسیم از کانی‌های پتاسیم‌دار و خاک کاراتر بودند به طوری که میزان پتاسیم قابل استفاده خاک در تلقیح با این جدایه‌ها در مقایسه با شاهد، حدود 29 درصد افزایش یافت. این تحقیق نشان داد که از برخی باکتری‌های ریزوسفر توتون می‌توان در متحرک نمودن منابع نامحلول پتاسیم خاک استفاده کرده و بخشی از نیاز گیاه توتون را که یک گیاه پرنیاز نسبت به پتاسیم است، تامین نمود.

    کلیدواژگان: شاخص حلالیت، کانی پتاسیم دار، محیط کشت
  • سیدعلی چاوشیان، پری سیما کتیرایی * صفحات 501-520

    هدف این مقاله معرفی، ارزیابی و کاربرد انواع مجموعه داده‌های بارش دیدبانی زمینی و ماهواره‌ای معتبر است که بر روی ایران داده مستمر و به روز دارند. تولید و کاربرد مجموعه‌های بارش بر اساس داده‌های ماهواره‌ای به دلیل تفکیک مکانی و زمانی بالا و همچنین پوشش مکانی تقریبا کامل جهانی در سال‌های اخیر به سرعت رو به گسترش است. در این مقاله توزیع مکانی هفت مجموعه بارش جهانی دیدبانی بر روی ایران با داده‌های باران‌سنجی در 228 پیکسل 0/25 درجه طول و عرض جغرافیایی که حداقل شامل سه باران‌سنج هستند مقایسه و بررسی شده است. مقایسه این نتایج نشان می‌دهند که مجموعه‌ها اختلاف زیادی در مقدار بارش سالانه بر روی پهنه ایران نشان می‌دهد (mm 180-260). این اختلاف در کرانه دریای خزر بالغ بر80 درصد میانگین بارش سالانه (حدود 300 میلی‌متر در سال) می‌رسد. داده‌های ماهواره‌ای روی منطقه سواحل دریای خزر و مناطق پر ارتفاع کوه‌های زاگرس واقع در جنوب غرب ایران بارش را با دقت کمتری نسبت به سایر نقاط برآورد می‌کنند. مجموعه‌های بارش زمینی بیشترین سهم از بارش سالانه را برای فصل بهار و سایر مجموعه‌ها بیشترین سهم را برای بارش زمستانی نشان می‌دهند. مقایسه بارش ماهانه، فصلی و سالانه مجموعه‌ها با داده های باران‌سنچی نشان می‌دهد مجموعه‌های ماهواره‌ای که با داده‌های باران‌سنجی تصحیح شده‌اند نتایج بهتری حتی نسبت به مجموعه‌های بارش زمینی دارند. مجموعه‌های ماهواره‌ای حال حاضر نیز بیش از سایرین بارش را کم برآورد می‌کنند.

    کلیدواژگان: ارزیابی بارش، بارش ماهوار ه ای، سنجش از دور، مجموعه های بارش
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  • Reza Mazarei*, AbdAli Naseri, amir soltani Pages 379-389
    Introduction

    Surface irrigation systems are the oldest and common irrigation method. Surface irrigation is of low cost and energy requirements compared to sprinkler and drip irrigation systems. In general, a main large number of fields' data is needed to show the farm average condition. Infiltration parameters are one of the most important parameters in surface irrigation systems and it has led to increase the irrigation systems efficiency, especially since the characteristics of infiltration vary with time and place. The modified kostiakov-lewis equation is one of the most useful infiltration equations in surface irrigation. In the current study, the infiltration parameters of the modified kostiakov-lewis equation were determined with two sets of usual methods including direct methods such as two-point Elliot and Walker and Input-Output, computer models such as SIPAR_ID and IPARM. Finally, the results were compared with the results of field experiments.

    Materials and Methods

    The current field was irrigated three times from 14 September to 31 October 2016 at the R 5-22 farm located in Salman Farsi Agro-Industry sugarcane fields with age of Raton 2. To collect the required data, the fields experiments were conducted on nine furrows of 250 m in length, 1.83m in space and 0.04% in slope, which all furrows were irrigated under three events and three inflow (1, 1.5 and 2 l/s), and fields’ data were obtained from experimental measurements during summer and autumn2016 at sugarcane fields of Salman Farsi Agro-Industry %. In the current study, the inflow rate and runoff were measured by W.S.C type 1 and 2 and all furrows divided into 10 stations. The advane time and infiltrated depth were measured at each stations. In this study 18 furrows were considered, nine furrows were used for testing and the other furrows had buffer roles. The furrows were irrigated by closed-end method. In this study, three indicators of infiltrated volume in the root zone, advance time and runoff volume were used to evaluate the accuracy of estimation of infiltration parameters. Surface irrigation model: WinSRFR 4.1.3 was used to simulate irrigation phases and infiltration value in each method. In this study, zero inertia model was used for simulation.

    Results and Discussion

    Results of this study showed that using the direct methods to estimate the infiltration parameters in WinSRFR 4.1.3 software improves the simulation process significantly. The results of the Two- Point and Input-Output method were showed a little difference with the results of the WinSRFR 4.1.3 software in simulation of the closed-end furrow irrigation process with sugarcane cultivated in furrows. The direct methods for infiltration parameters in furrow irrigation showed more accuracy than computer models in advance time , runoff and infiltrated water volumes. According to the results of this study, the Two-Point method in estimation of advance time with mean of RMSE, MAE and RE of 10.52, 14.91 and 10.1%, infiltrated water volume with mean of RMSE, MAE and RE of 9.6, 7.36 and 7.8 and runoff volume with mean of RMSE, MAE and RE of 8.8%, 8.7% and 1.2%, had a very acceptable performance. Also, the RMSE and RE values of other direct method (input-output method) were 11.4% and 6.8% for infiltrated water volume, respectively, and 1.6 and 0.3% for runoff volume, respectively, shows that this method has high accuracy in estimating these two performance indicators although this method with an average of 25.11% and 27.2% was not able to accurately simulate advance time. On the other hand, the results of computer models showed that the IPARM model with the average mean absolute error and relative error was 23.33, 15.5% of the advance time, 20.02 and 26.7% of the infiltrated volume and 11.81% and 1.8% estimated runoff volume, which was better than the SIPAR_ID model. Although computer models had acceptable performance in estimating infiltration parameters, direct methods performed better due to the use of more input data and data from all stages of irrigation. In general results of this study were showed that, if the direct methods for infiltration equations used Instead of the computers models in the designing, simulation and evaluation of the furrow irrigation systems, increased the accuracy of results to significantly and will improve and increase irrigation performance indicators

    Keywords: Infiltration parameter, Inflow-outflow method, IPARM, SIPAR, ID, Two-point method
  • AliAsghar Ghaemi, Hamidreza Haji, H. Dehghani* Pages 391-404
    Introduction

    Creating a uniform and adequate moisture in the root zone is one of the most challenging issues in irrigated lands. Use of irrigation systems with high water efficiency, such as sub-surface drip irrigation is recommended as a solution to reduce water losses. Information on soil moisture variation is an important factor for managing and designing a subsurface drip irrigation system. This study was conducted to evaluate the soil moisture variation for different irrigation regimes in a pistachio orchards equipped by a subsurface drip irrigation system (SDI).

    Materials and Methods

    This study was carried out in a two-hectare of 10 years old pistachio orchard located in Semnan province, Iran ( located at 35°28ˊ N, 53°12ˊE and elevation of 1160 m above sea level) during the 2012-2013 growing season. The climate of the studied area is hot desert having an average annual precipitation of approximately 110 mm. Daily meteorological data such as the temperature, relative humidity, wind speed, rainfall, and solar radiation were collected from a meteorology station in farm. The soil was sandy loam textured with average field capacity and permanent wilting point of 12.23 and 5.01%, respectively. Subsurface drip irrigation system was equipped by EuroDrip Company emitters (PC2), inline, to a distance of 80 cm and with a discharge of 26.2 Lit/ hr installed at a depth of 40 cm. In this study, a factorial experiment in split plot design was used with three replications. Three irrigation treatments i.e. control (I1), Irrigation based on irrigation requirement (I2) and I2 plus leaching requirement (I3), and changes in the moisture front were investigated by weight sampling between two drip lines, between the trees rows, on the drip line and out of the drip line of each row, before and after irrigation and in development, middle and late season.

    Results and Discussion

    For the evaluated irrigation systems, increased levels of irrigation regime resulted in increased moisture content in the root zone. The higher average soil moisture (16.6 %) was measured after irrigation under I3. The I1 irrigation regime did not significantly change the soil moisture content in upper part of emitters before and after irrigation event. Average soil moisture content at different depths showed that the soil moisture content in 75 soil depth was significantly higher than that in 25 and 50 cm soil depth, which can be attributed to higher root water uptake by root in 0-50 cm soil depth. Bilateral impact of irrigation regimes and soil depth showed higher soil moisture content (19.3%) under I3 and 75 cm soil depth which may lead to deep percolation. Bilateral impact of irrigation regimes, soil depth, and time before and after irrigation event also resulted in higher soil moisture content (22.5 %) in 75 cm soil depth after irrigation under I3. The lowest soil water content (10.5 %) was measured in 25 soil depth before irrigation under I1.

    Conclusion

    The results of this study showed that I2 and I3 irrigation regimes did not show water shortage during growth season (before and after irrigation), but the I1 irrigation regime caused water scarcity. Therefore, the formation of continuous moisture profiles with low moisture in I1 irrigation regime was caused as a result of low irrigation during this period. Accumulation of moisture at depth of 50-75 cm from the soil surface, even under low irrigation conditions I1 irrigation regime, implies that irrigation time is not suitable for irrigation regimes. In general, in order to improve the irrigation management, it is necessary to reduce the irrigation intervals and have a more appropriate distribution of moisture in the soil profile

    Keywords: leaching Requirement, Moisture Front, Soil Depth, Subsurface Drip Irrigation, Irrigation time
  • R. Zamani*Ehsan Fathi, Samira Bayati, Pone Ghorbani Pages 405-417
    Introduction

    Surface water, especially rivers, are the important sources for drinking water, agricultural and industrial uses. These reservoirs are easily affected by pollution and various activities. The vulnerability of surface water is greater than that the groundwater. Therefore, the importance of water quality evaluation, especially for drinkable water, has increased due to the reduction in its quality and quantity in recent years. Optimal use and conservation of water resources in terms of quantity and quality are the principles of sustainable development of any country. Water quality indices are among the useful tools in water quality assessment and management. The aim of this study was to evaluate the water quality of the Beheshtabad River in Chaharmahal and Bakhtiari Province, Iran by using the Liou Pollution Index and selecting the most important parameters based on Principal Component Analysis (PCA).

    Materials and Methods

    In this study, 7 water quality parameters including temperature, dissolved oxygen, biological oxygen demand, ammonia nitrogen, electrical conductivity, total suspended solids, and potential hydrogen were measured by standard methods along the river in 7 selected stations for 6 months (April to September 2016). Some of these parameters were measured at the sampling site and others in the laboratory. Then, the values of the Liou Pollution Index were calculated to evaluate the water quality of the Beheshtabad River in different stations. In this study, SPSS software was used to analyze the principal component. In the next step, the appropriateness of the statistical universe was assessed using the Kaiser-Meyer-Olkin test.

    Results and Discussion

    The results of this study showed that the water quality was good during the study period at sampling stations\, according to the Liou Pollution Index. The value of Liou Pollution Index was in the slightly polluted class in March in station 4. Then, the average of Liou Pollution Index in the Beheshtabad River was compared to different rivers. The result showed that the average of Liou Pollution Index in the studied river is higher than rivers outside Iran. In addition, according to the statistical technique of PCA, two components were introduced as the main component. The first component expressed 57.26% of the total variance and included dissolved oxygen, ammonia nitrogen, biological oxygen demand, electrical conductivity, total suspended solids and potential hydrogen parameters. The second component, temperature, expressed 21.3% of the total variance. Furthermore, the result of comparing the measured quality parameters with the standard value of surface water showed that biological oxygen demand, electrical conductivity, and total suspended solids parameters in some stations were within the standard range and in some others were higher, which indicated a negative result. The best and worst water quality in terms of biological oxygen demand was observed in May and June, respectively. The electrical conductivity in April and May in all stations was within the standard range. However, electrical conductivity was higher than the standard level in June in stations 4 and 5, higher again in July and August in stations 4 to 7, and higher as well in September in stations 2 to 7. The fish farming workshops, industrial pollution and geological survey may be the reasons. The value of potential hydrogen in all of the stations was within the standard range of 6.5 to 9.5. The value of dissolved oxygen was high because of increasing rainfall and stream flows due to the snow melting.

    Conclusion

    The results of this study showed that the water quality in the Beheshtabad River did not change during the last 6 months (April to September 2016), and water quality was good. In addition, PCA plays an important role in prioritizing the importance of each parameter in the pollution. Therefore, PCA places more important parameters in the first component and less important parameters in the subsequent, respectively. On the other hand, the measurement of physicochemical parameters is important for the study of water quality. This research demonstrates the usefulness and efficiency of the multivariate statistical technique of PCA and the use of indicators for effective management of surface water quality. Therefore, using water resources in the future is possible, and does not endanger their management based on sustainable development

    Keywords: Chaharmahal, Bakhtiari Province, Physicochemical parameters of water, River pollution index, Water resources
  • mohammadreza dalalian*, fatemeh zabihi, anvarossadat paknejad, mina khoshkhan Pages 417-430
    Introduction

    Destruction of soil structure and reduction of soil organic matter are major problems of cultivated soils which result from improper tillage operations, excessive consumption of chemical fertilizers and low consumption of organic and green fertilizers. One method for maintaining sustainable agriculture is to add organic and inorganic amenders. By producing resistant aggregates, organic matters improve soil structure and enhance soil permeability, FC moisture and water availability capacity. Furthermore, through enhancing organisms’ activities, especially earthworms, organic matters improve soil hydraulic conductivity and reduce bulk density. Organic matters may be added to soil through different way, however, the effect of each one on the soil’s physical properties is different. Chicken feather (CF) is readily available through henhouses and slaughterhouses, however, significant amounts of CF are destroyed by burning and burying them. Potassium Humate (PH) is a potassium salt from humic acid. Humic acid is extracted from various natural sources such as humus, peat, lignite and coal. Vermicompost (VC) is a compost which is produced by a non-thermal process. The impact of CF on different soil properties has not been studied yet. Accordingly, we investigated the impact of adding differing weight percentages of three types of amenders (PH, CF and VC) on the physical properties of soil under wheat cultivation at different moisture levels.

    Materials and Methods

    The experiment was conducted in factorial form based on randomized complete block design with 27 treatments in three replications. The first factor included the above-mentioned amenders; the second factor included three weight levels of these amenders (0%, 2.5% and 5%); the third factor included three moisture levels (0.5FC, 0.7FC and 0.9FC). The amenders were uniformly mixed with the soil up to the depth of 10 cm; then, wheat seeds were planted and moisture treatments were carried out during the growth period (from late April 2016 to September 2016). The soil moisture of the plots was controlled during the experiment period using the gravimetric method. For investigating the changes in the soil’s physical properties, samples (disturbed and undisturbed) were taken from the plots before and after the experiment. The following physical parameters were measured: bulk density (BD), soil moisture in field capacity (FC), permanent wilting point (PWP), wet aggregate stability (WAS), saturated hydraulic conductivity (KS), penetration resistance (PR), retention curve slope at inflection point (Si), mean weight diameter of aggregates (MWD) and mass-size fractal dimension of aggregates (Dm). Statistical analysis was done by SPSS software and means were compared via Duncan test. Tables and graphs were generated by Excel software.

    Results and Discussion

    Variance analysis and means comparison indicated that using amenders reduced bulk density for 89%. Reduced bulk density was caused by high keratin (91%) in CF, high porosity and the production of coarse pores in soil. On the other hand, VC with many pores led to increased aggregation and reduced bulk density.
    Results revealed that consuming CF increased soil moisture to field capacity (FC) (87%). CF had more significant impacts on increasing FC at high moisture levels. Thanks to its keratin structure, feather operates like a sponge which enhances soil porosity; hence, it absorbs more moisture and improves FC. Furthermore, results indicated that increasing the amounts of amenders led to increased soil moisture in PWP (91%). By increasing the amount of amenders in soil, aggregation and soil porosity increased which led to enhanced PWP.
    Large amounts of CF, PH and soil moisture (0.9FC) resulted in 3.7 times enhancement of Ks. CF led to the production of large soil pores and reduced soil density which resulted in improved soil structure and increased Ks. Thanks to its adhesion properties, PH increased Ks.
    Increasing the amount of amenders and the level of soil moisture in all three types of organic matters (especially CF) caused the 2.5 times enhancement of WAS.
    The results revealed that increasing soil moisture and amenders led to reduced Si (101%). Given all three types of amenders, PH had the highest impact on the reduction of Si. Moreover, soil penetration resistance (PR) was reduced as a function of increasing the soil moisture level.
    Contrary to the expectation, MWD was reduced as a result of increasing amenders. Furthermore, it was found that, given little soil moisture, increasing the amount of amenders resulted in increased Dm; however, given high soil moisture, increasing the amount of amenders led to decreased Dm. Thus, it should be noted that adding amenders improved the stability of aggregates over long time periods and at high soil moisture levels.

    Conclusion

    One major strategy for improving soil physical and chemical properties is using modifiers, especially organic matters. In this study, we investigated the impact of chicken feather on physical properties of soil and compared its effect with those of potassium humate and vermicompost under different levels of soil moisture and wheat cultivation.
    The results indicated that consuming amenders resulted in reduced Bd but increased FC, PWP, Ks and WAS.
    In other words, it improved physical properties of soil. Moreover, Si decreased as a result of increasing soil moisture and organic matters. Among the three types of amenders, potassium humate had the highest impact on reducing Si. PR was reduced as a function of increasing soil moisture. However, increasing organic matter led to decreased MWD. Furthermore, it was unexpectedly found that, given low soil moisture, Dm increased as a result of increasing the organic matters weight. Nevertheless, in high levels of soil moisture, Dm ​​decreased as a function of increasing organic matter. Thanks to positive impacts of organic matters (especially CF which is cheaper and more accessible than other amenders) on soil’s physical properties, they are highly recommended for soil improvement. Regarding future studies, investigation of the effect of these amenders on soil chemical properties under different soil textures is suggested

    Keywords: Amenders, Organic fertilizers, Soil moisture, Soil structure, Stability of aggregates
  • samira salari, Pejhman Tahmasebi, Farzaneh Nikookhah, Mehdi Pajouhesh* Pages 431-443
    Introduction

    Although many studies have been done on the effects of agricultural land abandonment, there is very little information about the impact of climate conditions on the restoration of abandoned agricultural lands. Human has changed most of rangelands to agricultural lands causing a decrease in carbon sequestration, depending on land management and tillage operations. One of the methods for rebuilding the land cover is the land abandonment, which results in enhanced organic carbon and decreased CO2 emission. Understanding the storage and dynamics of soil organic matter, especially in relation to changing land use, is fundamental to evaluate the role of soil as a carbon source or sink. After land use change from rangeland to cropland, agricultural practices decrease the C stored in soils and cause a net release of C into the atmosphere, which has strongly influenced the atmospheric CO2 levels and global C balance over the last centuries. For this purpose, this study aimed to assess the effect of interaction between agricultural land abandonment and climatic conditions on organic material reserves of primary soil particles.

    Materials and Methods

    The study area was located in semi-steppe rangelands of Sheida and Khargosh in about 60 km northwest of Shahrekord city, Chaharmahal-va-Bakhtiari province, central Iran. In this study, four treatments including rangeland, agricultural and cultivated land abandoned in the time series of 10-15 and 15-40 Year were selected. The sample plots were placed in the distance of transects, and the soil samples were collected from 0-30 cm depths with different rainfall conditions from two above-mentioned regions in three replications. For each region, the soil samples were transferred to the laboratory and then analyzed. The selected locations had same soil shape, topography, parent material, and slope. The soil samples of three plots were then combined and 24 samples were prepared. The distribution of carbon and nitrogen concentrations was determined at different soil particle components.

    Results and Discussion

    The results showed that the rangeland change to cultivated land did not have a significant effect on the amount of organic carbon, total nitrogen, and total carbon to total nitrogen ratio. However, the values of these indicators decreased significantly in the Sheida region. Under all land management, the amount of carbon and nitrogen of soil particles increased with decreasing the particle size from sand to clay. Hence, the abandoned agricultural land and rangelands did not significantly affect the amount of carbon and nitrogen concentration in sand, silt and clay particles. The amount of carbon, however, increased with the abandonment time and non-agronomic activity of carbon in sand and silt particles, although the carbon content of clay particle was not influenced. Agricultural practices may negatively or positively impact natural ecosystem depending on climatic condition and soil quality in unchanged lands. However, despite suitable climatic conditions (in terms of precipitation) and land cover in the rangelands over Sheida, the cultivation adversely influenced the soil quality and organic matter of the unchanged land. Although, the precipitation and soil quality were relatively lower in Khargosh region, the agricultural activities seem not to negatively affect the land quality. Moreover, rangelands change to cultivated lands did not have a significant effect on the amount of soil nitrogen in this region. The greatest nitrogen amount was measured in clay fractions of cultivated and abandoned lands for 40 years, and the minimum nitrogen content was detected in sand particles of lands abandoned for 15 years. The highest and lowest amount of nitrogen over all three fractions was, respectively, found for unchanged and abandoned lands in Sheida region. Therefore, the cultivated land depending on climate condition and management may considerably increase or decrease the organic carbon content in sand, silt and clay particles.

    Conclusion

    The results indicated that the agricultural land abandonment may differently affect the rangelands restoration measures such as the vegetation reclamation and soil carbon sequestration depending on climatic condition

    Keywords: Agriculture land abandonment, Organic carbon, total nitrogen, Soil particle
  • Akbar Karimi, Mostafa Chorom, Naeimeh Enayatiz, abdolamir moezzi* Pages 445-461
    Introduction

    Zinc is a key micronutrient which takes part in plant physiological functions. One of the extensively wide range abiotic stresses arises from Zn shortage in agricultural calcareous soils. Zn is one of the most prevalent disorders among various crops. Zinc deficiency is very common in most calcareous soils. Different mechanisms are involved in the deficiency of Zn In calcareous soils. The presence of calcium carbonate, lack of organic matter and high pH lead to Zn deficiency. Knowledge on the total Zn contents of in soil gives little information for their bioavailability. In order for better understanding availability of Zn to plant, knowledge about their mobility, and distribution in soil fractions is necessary. Biochar is a carbon-rich material produced by pyrolysis of biomass under oxygen-limited conditions and relatively low temperature. Biochar as a valuable soil amendment has received much attention due to its beneficial effects on carbon sequestration, soil physiochemical properties, soil microbial activity as well as soil fertility. Pyrolysis temperature has a significant influence on biochar physicochemical properties. Furthermore, biochar may alter the distribution of Zn fractions in calcareous soils. The impact of produced biochars at different pyrolysis temperature on distribution of Zn fractions in calcareous soils has been less studied. Therefore, the objective of this research was to evaluate the changes in distribution of Zn fractions in a calcareous soils treated with sugarcane bagasse derived biochars at different pyrolysis temperature.

    Materials and Methods

    An incubation experiment was carried out in laboratory condition as a factorial experiment based on a randomized complete design with two factors: (1) biochar type in four levels including control (without biochar) and biochar produced at 200 (B200), 350 (B350) and 500 ˚C (B500), (2) biochar application rate in two levels including 1 and 2% (w/w), and in three replications. Biochars were produced at 200, 350 and 500˚C pyrolysis temperatures under slow pyrolysis conditions with a heating rate of 5 °C min−1. Heating at this temperature lasted for 2 h. Then biochars were sieved to pass through 2 mm sieve and some properties were measured using the standard methods. The soil used in this study was sampled from the surface layer (0 to 20 cm depth), then, air-dried and sieved through 2 mm. Biochars produced at 200, 350 and 500˚C were mixed at 1 and 2% (w/w) with the 300 g of soil sample and incubated in ambient temperature at laboratory conditions (25 ± 2°C), for 90 days. Soil moisture content was maintained at 80% of field capacity. The samples were weighted every day and the required amounts of distilled water were added. At the end of incubation period, soil samples were air-dried and soil chemical parameters such as pH, cation exchange capacity (CEC), total organic carbon (TOC) and dissolved organic carbon (DOC) were measured.Chemical fractions of Zn in the incubated soil were determined according to the Tessier fractionation method. The Tessier sequential extraction method categorized Zn into 5 different fractions including: the exchangeable (Exch), bound to carbonate fraction (Car), bound to organic matter (OM), bound to Fe and Mn-oxides (FeMnOx) and residual fraction (Res).

    Results and Discussion

    Result indicated that application of different biochars significantly increased soil CEC and TOC. Maximum CEC and TOC were measured in B200 and B350 treatments, respectively, while their minimum values were observed in control treatment. In B200 treatments (B200, 1% and B200, 2%), pH significantly decreased compared to control, while this value significantly increased in B350, 1% , B500, 1% and B500, 2% treatments. B350 1% treatment did not have a significant effect on the soil pH. Application of 1 and 2% B200 significantly enhanced DOC (23.9 and 38%, respectively), compared to the control, but increase of DOC in B350 and B500 treatments was not significant compared to the control. Results showed that concentration of exchangeable Zn fraction decreased by 9.3, 19.5 and 9.5 % in B350, 2%, B500, 1% and B500, 2% treatments, respectively, compared to the control. However, B200 treatments (B200, 1% and B200, 2%) caused a significant increase in concentration of exchangeable Zn fractions (12.5 and 21.6%) compared to the control. The concentration of OM and Car Zn fractions increased in all biochar treatments compared to control. The highest concentration of OM and Car Zn fractions was observed after application of 2% B200 and 2% B500, respectively. Results showed that application of B350 and B500 had no significant effect on concentration of FeMnOx Zn fraction, while, this concentration significantly increased after B200 was applied. There were no significant (P ≤0.05) differences in concentration of residual Zn fraction among all the biochar treatments. The mean comparison results showed that the concentration of residual Zn in B200 treatments was significantly (P ≤0.05) lower than B350 and B500 treatments. There were no significant differences in this concentration among B500, B350 and the control treatments. Results revealed that in all treatments, different Zn fractions in the soil were distributed in the following order: Res > FeMnOx > Car > OM > Exch. The largest effect of biochars on the change in distribution of Zn fractions of soil was observed at 2% application rate.

    Conclusion

    It can be concluded that biochar B200 application could be an effective amendment for improving chemical properties and conversion of Zn from less available fractions to fractions with more bioavailability in the calcareous soil. Moreover, the biochar produced at 350 and 500˚C is better suited for enhancing soil organic carbon and Zn stabilization in calcareous soil.

    Keywords: Organic amendments, Pyrolysis temperature, Sequential extraction, Zinc availability
  • Hamid Zare Abyaneh, Farzaneh Heidari, Gholam Reza Heidari, mehdi jovzi * Pages 463-476

    In this pot experiment, the effects of three levels of zero (A0), three (A1) and five gram (A2) aquasorb superabsorbent per kg of soil, three levels of 70 (W1), 85 (W2) and 100 (W3) percent of irrigation requirements and two levels of 75 (F1) and 100 (F2) percent of nitrogen fertilizer requirements were studied on some traits of bell pepper plant. The experiment was factorial based on randomized complete block design with 18 treatments and three replications. The results showed significant effect of superabsorbent and irrigation treatments on all components except stem diameter. Among the superabsorbent treatments, the highest fruit yields (666.2 gr) and water productivity (12.36 kg/m3) were obtained in A2 treatment. Among the irrigation treatments, the highest values of the mentioned functions were obtained in the W3 and W1 treatments with 621.81 g and 10.57 Kg/m3 respectively. The effect of fertilizer treatments on shoot weight, root and fruit yield was significant. The highest fruit yield was 638.70 g in F2 treatment. The interaction of two variables of water with superabsorbent with effect on fresh and dry weight of shoot and root and on yield and water productivity yielded the highest fruit yield (916.65g) and productivity (14.55kg/m3) in A2W3 treatment. The interaction effects of superabsorbent and fertilizer showed that the highest yield and water productivity were equal to 670.51 grams and 12.44 kg / m3 in A2F2 treatment. The interactions of water and fertilizer showed that the highest yield and water productivity were 625.59 g in W3F2 and 12.32 kg/m3 in W1F2 treatment. The interaction of three superabsorbent, water and fertilizer variables on all studied traits was not significant

    Keywords: Fruit yield, Greenhouse, Root, Shoot
  • Mehdi Rahmati, Iraj Eskandari, Vali Feiziasl, Mehdi Kousehlou* Pages 477-478
    Introduction

    Soil is one of the nonrenewable resources (in human being life time scale) that is important to be protected. Tillage operations are carried out in a variety of ways, which in general can be divided into two comprehensive classes of conventional and conservation tillage practices. The tillage has a very important impact on soil physical, chemical and biological properties. Different tillage systems can have conflicting effects on soil physical properties, which is thought to reflect the impact of different weather conditions. Therefore, it seems necessary to study the effects of different tillage practices on the soil attributes in different climatic conditions.

    Materials and Methods

    This experiment was conducted for five years from 2011 to 2016 in a randomized complete block design (RCBD) with repeated measurements in two different locations and four replications. The applied tillage practices included no-till in standing residue (NT1), no-till in entire residue (NT2), chisel plow plus disc harrow (CH), minimum tillage with mulch cultivator (MT) and conventional plowing with moldboard plowing (CT). The experiment was carried out at Dryland Agricultural Research Institute (DARI) in Maragheh. Soil samples were taken at the end of fifth year and then soil texture were determined by hydrometer method, weight and geometric means of aggregates diameters by wet-sieving (MWDwetو GMDwet) and dry-sieving (MWDdry GMDdry) procedures, the stability of 1 to 2 mm aggregates (WAS) by wet-sieving, total soil organic carbon (TOC) by wet oxidizing method, dissolved soil organic carbon (DOC) using carbon analyzer and mass fractal dimension aggregates using Tyler and Wheatcraft model. The soil bulk density (Db) was also measured by intact samples (from two depths of 0-15 cm and 15-30 cm) prepared from the study area using sampling cylinders with a diameter of 5 and a height of 4 cm.

    Results and Discussion

    In general, the results showed that the interaction of depth and location on Db was significant at 5% probability level. The measured Db in 15-30 cm was greater than the measured Db in a depth of 0-15 cm. Also, in spite of the significance of the main effects of location and tillage and the interaction of tillage-location on soil dissolved organic carbon (DOC), tillage treatments and their interaction effects on total organic carbon (TOC) were not significant. The results showed that conventional tillage, CT, had the highest amount of DOC. However, no-till in entre residue (NT2) and minimum tillage (MT) showed the lowest amount of DOC. Further, the main effects of tillage practices on MWDdry and GMDdry were significant at 5% probability level. No-till (NT1 and NT2) practices had the highest MWDdry with values of 1.17 and 1.25 mm. Tillage practices and location had no significant effect on WAS, Dm, and MWDwet and GMDwet.

    Conclusion

    It seems that the reason that DOC content of CT was higher than conservation tillage practices is due to the preservation of crop residues on the soil surface in conservation and no-till systems and less mixing of them with soil and consequently their less decomposition. While in conventional tillage, plant residues were mixed with soil, and the effect of biological degradation increased soil DOC. The greater MWDdry in NT1 and NT2 practices suggests that tillage, even at a minimum or reduced state, breaks down the aggregates and produces smaller particles or aggregates. It also seems that the main reason for GMDdry reduction in minimum tillage is due to the further degradation of aggregates by the tillage agent. Therefore, to better and more accurately observe the effects of different types of tillage, sampling should be done at the end of each growing season

    Keywords: Aggregates stability, Bulk density, Dissolved organic carbon, Fractal dimension
  • Ebrahim Sepehr, Abas Samadi, Mohsen Barin, behnam Dovlati, MirHasan Rasouli, R. Ranjbar* Pages 489-500
    Introduction

    Potassium (K) is one of the major essential macronutrients for plant growth. Soil has rich reserves of K, among which only 1–2% can be directly absorbed by plants. It may be more economically viable to transform the fixed slow-release K into available K that can be absorbed by plants. The ability of some microorganisms to dissolve soil K-bearing minerals, such as micas is an important feature for increasing the yield of high-K-demand crops such as tobacco. Also, these microorganisms have both economic and environmental advantage. A large number of saprophytic bacteria such as Bacillus mucilaginosus and fungal strains such as Aspergillus spp. are known for their potential in releasing insoluble native K-source in soil into a plant available nutrient pool. Tobacco (Nicotiana spp.) is one of the most important industrial crops. K plays a vital role in increasing the tobacco yield and controlling quality parameters such as leaf combustibility that is one of the key criteria taken into account by the tobacco industry for assessing quality. Thus, high ranges of K fertilizers are applied in tobacco fields based on plant K requirement to build up soil K in tobacco producing countries. Increasing cost of the fertilizers and environmental risks necessitates alternate means to fertilizers such as application of microorganisms. The use of chemical K fertilizers can be reduced by exploiting the potential of bio-inoculants which are inexpensive and eco-friendly. Information related to K-solubilizing microorganisms in tobacco rhizosphere and their suitability in increasing the available K in tobacco-cultivated soils is not well-documented. Hence, the present study was conducted to screen the KSB isolates from tobacco-cultivated soils and evaluate their potential in dissolving K bearing silicate minerals and increasing soil available potassium.

    Materials and Methods

    Soil samples were randomly collected from the rhizosphere of tobacco from 25 different locations in northwest of Iran. The serial dilutions of the soil samples were made up to 10-4 and 5 µl of diluted soil suspension plated on Aleksandrov medium plates (on the agar-based culture medium). Aleksandrov medium contained 5.0 g Glucose, 0.5 g MgSO4.7H2O, 0.1g CaCO3, 0.006 g FeCl3, 2.0 g Ca3PO4, 2.0 g insoluble mica powder as potassium source and 20.0 g agar in 1 liter of deionized water. The plates were incubated at 28±2°C in incubator for 10 days. Finally, nine isolates of potassium silicate solubilizing bacteria were isolated and purified. Solid and liquid Aleksandrov media were applied for qualitative (Solubility Index = Diameter of zone of clearance/ Diameter of growth) and quantitative (K content) evaluation, respectively, based on the completely randomized design (CRD) with three replication. Liquid Aleksandrov medium containing 2 g L-1 of mica and feldspar mixture, was inoculated with bacterial isolates. Bacterial isolates creating high solubility index and releasing more K from K-bearing minerals into liquid medium, were selected as effective isolates. In order to evaluate the efficiency of the potent bacterial isolates for increasing soil available K, an experiment was conducted with three replication and eight potent bacterial isolates along with a control (non-inoculated soil). Sterilized soil samples were inoculated with bacterial isolates separately and incubated at 25°C, with 75% field capacity moisture levels for 90 days. After incubation, available K in soil samples were extracted with Ammonium Acetate 1M. Variance of solubility index, K concentration into liquid Aleksandrov medium and soil available K were analyzed using SPSS (Statistical Package for the Social Sciences). Student-Newman-Keuls (SNK) test comparisons were also used to compare available soil K using SPSS 16.0.

    Results and Discussion

    Eight KSBs isolates, including KSB20, KSB30, KSB40, KSB22, KSB42, KSB90, KSB92 and KSB10, were isolated and purified as effective isolates for dissolving mica and feldspar minerals. Most isolates were gram-positive, rod-shaped, and white in appearance. The studied isolates, except KSB22, KSB40 and KSB20, had α-amylase enzyme activity. Bacterial isolates, including KSB20, KSB30, KSB42 and KSB10, were significantly superior in sucrose and glucose hydrolysis. The isolate of KSB10 also had fluorescence properties. The highest solubility index (2.8, 2.7 and 2.5) was obtained from the activity of KSB22, KSB42 and KSB10 isolates in solid Aleksandrov medium, respectively. The highest concentration of potassium into liquid Aleksandrov medium was found for the KSB42 and KSB10 isolates (9.40 mg L-1). The KSB42 and KSB10 isolates increased medium K concentration approximately three times more than non-inoculated medium. In addition, KSB42 and KSB10 isolates were more effective in releasing potassium from soil potassium-bearing minerals. The amount of available potassium in soil incubated with KSB42 and KSB10 isolates increased by 44 and 46 mg kg-1 compared to the control, respectively.

    Conclusion

    Among bacterial isolates purified from the tobacco rhizosphere, the KSB42 and KSB10 isolates increased more significantly the solubility of potassium minerals and potassium availability in soil compared to other isolates. These bacteria isolates increased potassium concentration into Aleksandrov liquid medium by more than three times and also increased soil available potassium by about 44 to 46 mg kg-1 compared with the control. As a result, these isolates (KSB42 and KSB10) can be used as a bio-fertilizer to reduce potassium fertilizer application and increase the quality of tobacco after field experiments

    Keywords: Potassium, Potassium solubilizing bacterium, Silicates minerals, Tobacco rhizosphere
  • Ali Chavoshian, P.S. Katiraie* Pages 501-520
    Introduction

    Precipitation has an important role not only in the variety of scientific applications including climate change, climate simulations, weather modeling, and forecasting but also in decision making such as water management, hydrology, agriculture, drought, and crisis management. Different temporal resolutions and coverages of data are required for this and other applications. For example, long term meteorological data are needed for monitoring the climate variability and trends and for climate simulation assessments in local and global scales. Also, present data are used to assimilate into forecast models to improve the predictions. Historical and present precipitation data are the main requirements to monitor and predict droughts which help to early warning system and water management decisions in a country. The recent rainfall data are also the primary input of hydrological models to flood forecast in a basin. The accurate estimation of precipitation amount is vital for these applications.

    Materials and Methods

    However, rainfall is discontinuous and varies greatly both in time and space which makes it parallel with difficulties in the actual measurements. The two main sources of observational precipitation datasets are ground-based rain gauge measurements and space-based remote sensing satellite estimations each one with its own limitations and strengths. Historically, rain-gauge measurements have been considered as the “ground truth”, but they have mostly limited to land surface, the measurements are sparse or nonexistent in some regions like deserts or high topographic areas. Although rain gauges measure rainfall directly, their data are only representative for a limited spatial extent and may be subjected to some errors caused by local effects such as topography or wind-induced undercatch. An alternative approach which can provide relatively homogenous estimates with complete coverage over most of the globe is based on using satellite observations. Therefore, satellite data are capable to estimate precipitation over the oceans and over remote areas where few or no ground measurements are available. The satellite-based precipitation estimates are derived mainly from visible, infrared (IR) and passive microwave (PMW) radiances which are measured by satellites. Although the visible channels cannot be used at night, the IR data are available in fine spatial resolution (about 3-4 km) with high temporal sampling (15 min) which are provided by geosynchronous satellites. Another source of data is PMW that can be used to estimate rainfall more directly. Low-altitude polar-orbiting satellites serve to measure the PMW data. Although, the microwave sensors can penetrate into the clouds and provide more information about the cloud characteristics such as water vapor, cloud particles, and structure of hydrometeors, but at the expense of temporal sampling. In recent years, different algorithms have been developed using the combination of the IR, Visible (VIS) and PWM observations to provide more accurate rainfall estimations in high spatial and temporal resolutions. To demonstrate the similarities and differences between the spatial distribution of different satellite-based and gauge-based precipitation datasets over Iran we compared seven different datasets. For comparisons all datasets are regridded to 0.25-degree latitude longitude spatial resolutions. Then the spatial distribution of the mean and relative standard deviations of annual precipitation of these datasets have been calculated. We also used more than 2000 rain gauges to evaluate the selected datasets. To reduce error only 228 pixels, include at least 3 rain gauges are used for comparisons of spatial average of monthly, seasonal and annual precipitation of gauge and seven datasets.

    Results and Discussion

    The results showed a large amount of differences in annual precipitation between seven selected datasets. The most differences pronounce in wet areas in the north of Alborz Mountain, in the semi-arid and arid regions of the central desert and in the high mountainous areas of the southern Zagros. The reason for these differences is that not only satellite-based but gauge-based datasets have large uncertainties estimating areal precipitation in such high topographic areas. The satellite products are prone to some errors arising from not fully understood physical process, sampling error and parameter estimation. Therefore, verification of precipitation datasets is one of the most important parts of the data development and refinements. In this paper, the spatial distribution of seven different global-observational precipitation datasets over Iran are compared for the period 2003-2007. At first all datasets were regridded to 0.25° spatial resolutions using linear interpolation method. Then, the mean and relative standard deviation of annual precipitation of the datasets were calculated to analyze the spatial discrepancies between datasets. The areal average of annual precipitation and the contribution of seasonal precipitation were calculated for comparison purposes. The results showed that areal average of annual and seasonal precipitation for 228 selected pixels for PERSIANN-CDR, TRMM, and GPCP which are satellite-based and gauge adjusted datasets are more similar to the rain gauge data than other datasets. The results for the above datasets are even better than CRU and APHRODITE which are gauge-based datasets.

    Conclusion

    The results showed that the satellite estimates are not capable to show the precipitation (detection and amount) over the coast of Caspian Sea and the high areas of the Zagros Mountain as well as other parts of the country. There are some useful recommendations for data users at the end of this paper. In fact, in this paper our spatial focus is on Iran and we introduced a web address which data users can access freely from one of the most popular and widely used satellite-based products in easy-to-use format only for Iran. The results show considerable differences between the datasets. The difference is about 0.8 times of mean annual precipitation (about 300 mm in a year) for the coast of Caspian Sea. The satellite-based estimations were less accurate over the coast of Caspian Sea and high mountainous area of the southwest of Zagros comparing to other parts of the country. While spring precipitation shows maximum contributions in annul precipitation for in-situ datasets, winter precipitation shows maximum contribution in annual precipitation for other datasets. The results showed that areal average of monthly, seasonal and annual precipitation over 228 selected pixels for PERIANN-CDR, TRMM and GPCP were consistent with rain gauge data. CMORPH and PERSIANN underestimate areal average of monthly and seasonal precipitation over the pixels

    Keywords: Evaluation, Iran, Remote Sensing, Precipitation Datasets, Satellite-based Precipitation