فهرست مطالب

  • سال سی و سوم شماره 6 (بهمن و اسفند 1398)
  • تاریخ انتشار: 1398/12/20
  • تعداد عناوین: 12
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  • مونا احمدیان، مجید منتصری* صفحات 795-809

    سیستم مخازن ذخیره برای کنترل و تنظیم رژیم جریان رودخانه ها جهت تامین تقاضا برای مصارف مختلف شرب، کشاورزی و . . . طراحی و احداث می‏گردند. در این مطالعه سد مخزنی لار به‏ عنوان یکی از منابع اصلی تامین آب شرب تهران با استفاده از روش شبیه ‏سازی مونت‏کارلو مورد تجزیه و تحلیل قرار گرفته ‏است. بدین منظور با به‏کارگیری مدل استوکاستیک AR(1)، داده ‏های جریان سالیانه تولید و سپس مقادیر جریان سالیانه با استفاده از مدل توزیعی والنسیا-شاکی در ماه ‏های مختلف سال پخش یا توزیع شده ‏است. در مرحله بعد، داده‏های ماهیانه تولیدی به‏عنوان جریانات ورودی به مخزن ذخیره برای شبیه ‏سازی رفتار سد مخزنی لار با استفاده از روش 3Modified-SPA و با اعمال شاخص ‏های عملکرد سیستم مخازن به‏ کار گرفته شد. نتایج مطالعه نشان می‏دهد که حجم ذخیره علاوه بر تقاضا، تابعی از تلفات ناشی از تبخیر و ضرایب اعتماد زمانی و آسیب‏ پذیری بوده و از یک رابطه نمایی به‏ازای تقاضا تبعیت می‏کند. علاوه بر این در هر سه گونه‏ (version) SPAهای اصلاح شده (SPA-I, SPA-II, and SPA-III) دو شاخص عملکرد مخزن، یعنی؛ اعتمادپذیری زمانی و آسیب ‏پذیری قابل کنترل در تحلیل بوده و تحلیل سیستم ذخیره برای مقادیر معلوم یا مشخص شاخص ‏های مذکور انجام می‏ پذیرد. همچنین در روش‏های SPA-II و  SPA-III امکان استفاده از رابطه غیرخطی یا رابطه واقعی سطح-حجم در برآورد حجم تلفات ناشی از تبخیر در سیستم ذخیره است. کنترل دو شاخص عملکرد مخزن و به‏ کارگیری رابطه واقعی یا غیرخطی سطح-حجم مخزن در تحلیل سیستم مخازن ذخیره به ‏همراه جواب یکتا به‏ عنوان مزیت‏های اساسی و بسیار مهم روش‏ های مذکور نسبت به روش آنالیز رفتاری (فرض خطی بودن رابطه سطح-حجم مخزن و کنترل تنها شاخص اعتمادپذیری در محاسبات) است.

    کلیدواژگان: تولید داده، روش SPA، سد مخزنی لار، شبیه سازی مخزن، مدل استوکاستیک
  • رقیه نجفی پور، هادی رمضانی اعتدالی*، بیژن نظری صفحات 811-822

    کشت های گلخانه ای نقش ویژه ای در تولید محصولات کشاورزی دارند. آگاهی از میزان دقیق نیاز آبی در برنامه ریزی توسعه گلخانه ها از اهمیت زیادی برخوردار است. هدف از این پژوهش ارزیابی و ارایه مدلی برای برآورد تبخیر و تعرق خیار در شرایط گلخانه ای با استفاده از داده های هواشناسی و مطالعه بهره وری آب در تولید این محصول در قزوین است. در طی تحقیق، تغییرات دما، رطوبت، تشعشع، ارتفاع گیاه و رطوبت خاک اندازه گیری شد. با بررسی مدل های ریاضی مختلف، یک مدل توانی با پارامترهای دما، رطوبت نسبی و ارتفاع گیاه و با ضریب همبستگی 86/0 به عنوان بهترین مدل برای برآورد تبخیر و تعرق خیار گلخانه ای انتخاب شد. همچنین مقایسه تبخیر و تعرق اندازه گیری شده با روابط متداول تعیین تبخیر و تعرق نشان داد که در سطح اطمینان 99 درصد بین تبخیر و تعرق اندازه گیری شده و تبخیر و تعرق برآورد شده با روش فائو پنمن مانتیث همبستگی وجود دارد. روش فائو پن من مانتیث با ضریب تبیین 42/0 از دقت بیشتری نسبت به سایر روش ها برخوردار بوده و روش بلانی کریدل اصلاح شده با ضریب تبیین 24/0 کمترین دقت را دارد. همچنین بهره وری آب در گلخانه های کشت خیار فعال در استان قزوین مورد بررسی قرار گرفت. نتایج نشان داده بهره وری آب خیار در گلخانه ها از 23/9 تا 44/22 کیلوگرم بر متر مکعب متغیر است. این دامنه تغییرات مساله اهمیت مدیریت و بهره برداری در ارتقای بهره وری آب در گلخانه ها را خاطر نشان می سازد. طبق برآوردهای انجام شده در این تحقیق اگر میزان تولید فعلی خیار در استان در فضای آزاد در گلخانه ها کشت شود، به 117 هکتار گلخانه نیاز خواهد داشت و با این عمل نزدیک به 15 میلیون متر مکعب آب صرفه جویی خواهد شد. با بررسی سایر جوانب اقتصادی و اجتماعی توسعه گلخانه ها می تواند در تسکین مشکلات کم آبی در استان کمک ساز باشد.

    کلیدواژگان: تبخیر و تعرق، فائو-پن من-مانتیث، کم آبیاری
  • تهمینه رئیسی نژاد، نجمه یزدان پناه* صفحات 823-832

    با اعمال مدیریت صحیح آب در مزرعه می توان از منابع آب، خاک و کود استفاده بهینه نمود و تولید محصولاتی با کمیت و کیفیت بالا را امکان پذیر ساخت. در این راستا و به منظور مدیریت آبیاری گیاه آفتابگردان با استفاده از تنظیم پتانسیل آب خاک، سه سطح مکش (40=1I، 55=2I و 70=3I سانتی بار جهت شروع آبیاری) و دو سیستم آبیاری قطره ای (سطحی =1S و زیرسطحی =2S) به ترتیب به عنوان عوامل اصلی و فرعی مورد بررسی قرار گرفتند. این آزمایش در قالب طرح کرت های نواری یک بار خرد شده بر پایه طرح بلوک های کامل تصادفی، با سه تکرار در مزرعه تحقیقاتی شهرستان جیرفت در سال زراعی 1396 اجرا شد. نتایج پژوهش نشان داد که صرفه جویی 6/153 میلی متری آب (5/21 درصد) بین نقاط مکش 55 و 40 سانتی بار، باعث کاهش 5/12 درصد عملکرد دانه، 8/12 درصد تعداد دانه در طبق و 11 درصد ارتفاع بوته شد که افزایش 3/10 درصد در بهره وری آب را درپی داشت. این در حالی بود که اعمال سطح مکش 70 سانتی بار در مقایسه با سطح مکش 55 سانتی بار باعث کاهش 4/33 درصد عملکرد دانه، 9/22 درصد تعداد دانه در طبق و 5/22 درصد ارتفاع بوته شد و تنها افزایش 7/4 درصدی بهره وری آب را به دنبال داشت. از طرف دیگر، عملکرد دانه در آبیاری زیرسطحی به مقدار 499 کیلوگرم در هکتار بیشتر از آبیاری سطحی بود. این در حالی بود که با وجود صرفه جویی 10 درصدی مصرف آب در آبیاری زیرسطحی نسبت به آبیاری سطحی، بهره وری آب در این سیستم 5/21 درصد بیشتر بود. صفات ارتفاع بوته و تعداد دانه در طبق در آبیاری قطره ای زیرسطحی به ترتیب 2/8 و 7/8 درصد نسبت به آبیاری سطحی بیشتر بود. لذا انجام آبیاری قطره ای زیرسطحی در سطح مکش 55 سانتی بار برای کشت گیاه آفتابگردان در شهرستان جیرفت می تواند راهکاری مناسب برای صرفه جویی در مصرف و افزایش بهره وری آب در دوره های خشکسالی باشد.

    کلیدواژگان: آلودگی آب، سپیولیت، فلز سنگین، مدل باکس
  • مرضیه پیری، ابراهیم سپهر*، عباس صمدی، خلیل فرهادی، محمد علیزاده خالد آباد صفحات 833-844

    فرآیند جذب و استفاده از جاذب های ارزان قیمت برای حذف فلزات سنگین یکی از روش هایی است که در سال های اخیر توجهات زیادی را به خود جلب کرده است. در این تحقیق به منظور مدلسازی و بررسی اثر فاکتورهای pH، غلظت و قدرت یونی بر جذب فلزات سنگین سرب و کادمیم از محلول های آبی توسط رس سپیولیت، از روش سطح پاسخ بر مبنای مدل باکس بنکن استفاده شد. برای این منظور آزمایشات ناپیوسته جذب، با در نظر گرفتن دامنه های متفاوتی از این سه متغیر شامل pH (6-3)، قدرت یونی محلول (mol L-1 06/0-01/0) و غلظت فلز (mg L-1 200-0) اجرا گردیدند. نتایج نشان داد میزان جذب سرب و کادمیم با افزایش غلظت اولیه فلز و pH، افزایش و با افزایش قدرت یونی محلول کاهش یافت. آنالیز واریانس یک طرفه (0001/0>p) نشان داد مدل درجه دو بهترین مدل برای تعیین برهمکنش متغیرهای مورد مطالعه می باشد، این مدل حاکی از آن است که غلظت موثرترین عامل در حذف کادمیم و سرب به وسیله سپیولیت است. با توجه به مقادیر ضریب تعیین (99/0=R2) وR2 متعادل شده (98/0=R2adj) می توان گفت مدل بدست آمده برای تحلیل داده ها مناسب می باشد. شرایط بهینه برای جذب حداکثر سرب و کادمیم از محلول های آبی در pH=6، غلظت فلز (mg L-1) 200 و قدرت یونی محلول (mol L-1) 02/0 است. مقادیر پیش بینی شده جذب برای شرایط بهینه ذکر شده برای جذب سرب و کادمیم نیز به ترتیب 4/44 و (mg g-1) 28/34 بدست آمد. بطور کلی می توان گفت سپیولیت می تواند به عنوان یک جاذب ارزان قیمت و قابل دسترس برای جذب کادمیم و سرب از آب های آلوده استفاده شود.

    کلیدواژگان: آلودگی آب، سپیولیت، فلز سنگین، مدل باکس بنکن
  • محمدعلی محمودی*، سیده پریا نقشبندی صفحات 845-856

    فرسایش خاک یک تهدید زیست محیطی جدی است. یکی از مدل های تجربی پرکاربرد برای تخمین فرسایش خاک معادله جهانی فرسایش خاک بازنگری شده موسوم به مدل RUSLE می باشد. هدف از انجام این پژوهش تلفیق داده های بدست آمده از پیمایش صحرایی با داده های سنجش از دور جهت برآورد میزان فرسایش خاک با استفاده از مدل RUSLE در حوزه آبخیز سد گاوشان در استان کردستان بود. مقدار عامل فرسایندگی سالیانه باران با استفاده از داده های بارش ماهانه 11 ساله در 7 ایستگاه در اطراف حوضه محاسبه شد. سپس تغییرات مکانی آن با استفاده از کریجینگ معمولی برآورد شد. شاخص فرسایش پذیری خاک از نقشه خاک، که خود با استفاده از پیمایش صحرایی و داده های سنجش از دور تهیه شد، بدست آمد. عامل توپوگرافی از مدل رقومی ارتفاع با قدرت تفکیک مکانی 30 متر استخراج شد. عامل پوشش گیاهی سالیانه نیز از داده های سنجش از دور برآورد شد. از آنجایی که در حوضه مورد مطالعه عملیات حفاظت خاک ناچیز است، مقدار عامل حفاظت خاک در سرتاسر حوضه 1 در نظر گرفته شد. نتایج بدست آمده نشان داد که متوسط مقدار فرسایش سالیانه خاک در این حوضه 35/2 تن در هکتار است. با اینحال در نیمی از مناطق حوضه مقدار فرسایش سالیانه از 92/0 تن در هکتار کمتر است. نواحی با فرسایش خیلی زیاد در حدود 4 درصد از حوضه را در بر می گیرند که عمدتا در شیب های زیاد در قسمت های جنوب غربی حوضه واقع شده اند. بر اساس نتایج بدست آمده درجه شیب مهمترین عامل کنترل کننده شدت فرسایش خاک در این حوضه است.

    کلیدواژگان: حوضه آبخیز سد گاوشان، سنجش از دور، فرسایش خاک، مدل RUSLE
  • اژدر عنابی میلانی*، محمد زرین بال صفحات 857-871

    درخت بادام تحمل خوبی به کم آبی دارد و مناسب کاشت در مناطق خشک و نیمه خشک نظیر ایران است اما حساسیت آن به شوری، مدیریت آبیاری آن را با چالش هایی مواجه کرده است. این مطالعه با هدف بررسی تااثیر تنش هم زمان خشکی و شوری بر جذب آب، رشد رویشی و پتانسیل آب برگ درخت بادام در قالب طرح بلوک های کامل تصادفی با سه تیمار شوری آب، شامل آب چاه با شوری dS/m2 (T1)، و آب های شور شده با نمک هایی با همان ترکیب آب چاه dS/m4 (T2) و dS/m5 (T3) در سه تکرار در خاکی با بافت شن لومی اجرا شد. در طول فصل رشد، دما و رطوبت نسبی هوا، پتانسیل آب برگ (LWP) و رطوبت خاک (SWC) تا عمق 70 سانتی متر اندازه گیری گردید. نتایج نشان داد که شوری تاثیر معنی داری (P<0.01) بر LWP، رشد رویشی و مقدار آب باقیمانده خاک دارد. متوسط فصلی رشد طولی سرشاخه و رشد قطری تنه در درخت بدون تنش به ترتیب 104 سانتی متر و 53 درصد بود که در تیمار تنش هم زمان خشکی و شوری (T3) به ترتیب به 62 سانتی متر و 18 درصد کاهش یافت. متوسط فصلی LWP برای تیمارهای T1 تا T3 به ترتیب 78/1-، 93/1- و 16/2- مگاپاسکال بدست آمد. ارتباط معنی داری بین LWP با کمبود فشار بخار هوا و SWC حاصل شد. حد آستانه ای LWP برای شروع تنش، 78/1- مگاپاسکال بدست آمد. براساس پتانسیل آب برگ آستانه ای تنش، کمینه رطوبت حجمی خاک برای تیمارهای T1 تا T3 برای اجتناب از تنش به ترتیب 1/10، 8/11 و 5/13 درصد تعیین شد.

    کلیدواژگان: پتانسیل آب ساقه، رطوبت خاک، قطر تنه، کمبود فشار بخار
  • آمنه جهاندیده، مجتبی بارانی مطلق*، اسماعیل دردی پور، رضا قربانی نصرآبادی صفحات 873-884

    فسفر در مقایسه با دیگر مواد مغذی ضروری، دارای تحرک و قابلیت دسترسی کمتر برای گیاهان است. اگر چه فسفر به اشکال آلی و غیر آلی در خاک ها فراوان است، اما اغلب عامل مهم یا حتی محدود کننده اصلی برای رشد گیاه است. در این پژوهش اثرات مصرف هم زمان اسید هیومیک و کود فسفر و روش های کاربرد آن بر صفات فیزیولوژیک و فراهمی فسفر در گیاه کلزا (رقم هایولا 50) مورد بررسی قرار گرفت، بدین منظور آزمایشی به صورت فاکتوریل در قالب طرح کاملا تصادفی در 3 تکرار به صورت گلدانی به اجرا درآمد. تیمارهای شامل فسفر در سه سطح (0، 50 و 100 میلی گرم کود سوپرفسفات تریپل بر کیلوگرم خاک)، اسید هیومیک در سه سطح (0، 5/0 و 1 گرم بر کیلوگرم خاک) و روش های کاربرد همزمان اسید هیومیک و فسفر بود. اثرات متقابل اسید هیومیک و فسفر و روش های کاربرد آن بر تمام صفات اندازه گیری شده در سطح یک درصد معنی دار شد. نتایج اثرات متقابل سه جانبه سطوح اسید هیومیک، سطوح فسفر و روش های کاربرد نشان داد که بیشترین مقادیر در انواع کلروفیل (a، b و ab) و کارتنوئید در تیمار کودی 100 میلی گرم بر کیلوگرم فسفر و سطح 1 گرم بر کیلوگرم مصرف همراه با آب آبیاری اسید هیومیک به دست آمد. بیشترین مقدار غلظت فسفر اندام هوایی با میانگین 30/0 درصد در تیمار یک گرم بر کیلوگرم اسید هیومیک همراه با آب آبیاری با سطح 100 میلی گرم بر کیلوگرم فسفر مشاهده شد هر چند با تیمار 5/0 گرم بر کیلوگرم اسید هیومیک همراه با آب آبیاری از لحاظ آماری اختلاف نداشت. بیشترین مقدار فسفر عصاره گیری شده به روش اولسن با میانگین 16/41 میلی گرم بر کیلوگرم و روش سلطان پور و شواب با میانگین 24/5 میلی گرم بر کیلوگرم مربوط به تیمار 100 میلی گرم برکیلوگرم فسفر و مصرف خاکی یک گرم بر کیلوگرم اسید هیومیک بود. همچنین همبستگی بالا و معنی داری بین فسفر عصاره گیری شده به روش اولسن و سلطان پور و شواب با صفات مورد مطالعه مشاهده شد. به نظر می رسد که استفاده از فسفر همراه با اسید هیومیک، بیشتر از کاربرد فسفر به تنهایی، می تواند باعث افزایش فسفر قابل دسترس در خاک و نیز غلظت فسفر در گیاه کلزا (هایولا 50) شود.

    کلیدواژگان: اندام هوایی، کلروفیل، کارتنوئید، وزن تر و خشک
  • لیلی قربانی مینائی، مهدی ذاکری نیا*، عباس رضایی اصل، حمیدرضا میرکریمی صفحات 885-896

    با توجه به محدودیت منابع آب در کشور، استفاده از شیوه های نوین آبیاری برنج با مصرف کمتر آب امری بدیهی خواهد بود. یکی از راه های افزایش بهره وری آب، استفاده از روش آبیاری زیرزمینی است. همچنین برای مقابله با بحران آب می توان از آب های نامتعارف و به عبارت دیگر آب های با کیفیت نامطلوب استفاده نمود. به منظور بهبود کیفیت آب مصرفی در کشاورزی روش های مختلفی وجود دارد که یکی از آن ها استفاده از میدان های مغناطیسی است. در پژوهش حاضر اثر مغناطیسی شدن پساب تصفیه خانه شهری گرگان و آب معمولی به روش آبیاری زیرزمینی در پردیس کشاورزی دانشگاه علوم کشاورزی و منابع طبیعی گرگان بر صفاتی همچون عملکرد شلتوک، عملکرد بیولوژیک، شاخص برداشت، کارایی مصرف آب، بهره وری فیزیکی آب و بهره وری اقتصادی آب مورد بررسی قرار گرفت. آزمایش به صورت فاکتوریل در قالب طرح بلوک های کامل تصادفی در 3 بلوک، از اردیبهشت تا شهریور ماه سال 1397 انجام شد. تیمارهای آزمایش شامل  فاکتور نوع آب آبیاری در دو سطح شامل آب معمولی (C) و پساب تصفیه شده شهری گرگان (W) و فاکتور دوم شامل روش اصلاح آب در دو سطح شامل مغناطیس (M) و عدم مغناطیس (O) بود. نتایج مقایسه میانگین فاکتور نوع آب نشان داد که بین تیمار پساب و آب معمولی در پارامترهای اندازه گیری تفاوت معنی داری مشاهده نشد. فاکتور روش اصلاح آب نشان داد که تیمار غیرمغناطیس در پارامترهای عملکرد شلتوک، کارایی مصرف آب، بهره وری فیزیکی آب و بهره وری اقتصادی آب نسبت به تیمار مغناطیس معنی دار بود اما در پارامترهای عملکرد بیولوژیک و شاخص برداشت اثر معنی دار مشاهده نشد. همچنین مقایسه میانگین اثرات متقابل نوع آب و روش اصلاح بر همه پارامترهای اندازه گیری شده حاکی از برتری پساب غیرمغناطیس نسبت به بقیه تیمارها درسطح 5 درصد بود. براساس نتایج این تحقیق می توان گفت که کشت برنج از نظر آبیاری نیازی به ایجاد یک لایه ایستابی در سطح خاک ندارد و همچنین استفاده از پساب تصفیه خانه شهری گرگان به عنوان آب آبیاری، علاوه بر امکان کاهش برداشت از منابع آبی با کیفیت بالا، هزینه های مصرف کود (شیمیایی و آلی) در تولید محصول را نیز کاهش داد.

    کلیدواژگان: آبیاری زیرزمینی، پساب تصفیه شده شهری، پساب مغناطیس، زهکشی کنترل شده، عملکرد برنج
  • لادن حیدری، حسین بیات*، جواد حمزه ئی، تهمینه قیطاسی رنجبر، سمیه بهرامیان راغب، فاطمه مدینه خرمی صفحات 897-911

    علی رغم تاثیر قابل توجه قار چ ها و باکتری ها بر پایداری ساختمان خاک، تاثیر قارچ مایکوریزا گونه گلوموس موسه آ و باکتری ریزوبیوم بر ساختمان خاک، به ندرت مورد بررسی قرار گرفته است. آزمایش در قالب طرح بلوک های کامل تصادفی با سه تکرار در دو مرحله گلخانه ای و مزرعه ای با کشت نخود اجرا شد. در شرایط مزرعه تیمارهای آزمایشی شامل قارچ مایکوریزا گونه گلوموس موسه آ، باکتری ریزوبیوم، ترکیب تیمار اول و دوم (مایکوریزا-باکتری ریزوبیوم) و شاهد (بدون تلقیح) و در شرایط گلخانه علاوه بر چهار تیمار فوق تیمار ماده زمینه سترون شده قارچ مایکوریزا و تیمار بدون گیاه، تیمارهای آزمایشی بودند. مقدار کربن آلی و پایداری خاکدانه ها در حالت تر مورد بررسی قرار گرفت. نتایج گلخانه ای نشان داد که تیمار مایکوریزا نسبت به تیمار شاهد و شاهد بدون گیاه باعث افزایش معنی دار میانگین وزنی قطر خاکدانه ها (به ترتیب 6/51 و 1/189 درصد) شد. در شرایط گلخانه مقدار کربن آلی دارای همبستگی بالا با میانگین وزنی قطر خاکدانه ها (53/0R2=) بود و تیمار حاوی مایکوریزا باعث افزایش کربن آلی از 73/0 درصد در شاهد بدون گیاه به 02/1 درصد شد. در شرایط گلخانه تیمارمایکوریزا باعث افزایش خاکدانه های درشت و کاهش خاکدانه های ریز شد. همچنین استفاده همزمان باکتری و قارچ تاثیر کمتری بر پایداری خاکدانه ها نسبت به اثرات جداگانه آن ها داشت، زیرا استفاده همزمان، تاثیری بر رشد گیاه نداشت. در شرایط مزرعه تیمارها تاثیر معنی داری بر سایر کلاس اندازه خاکدانه ها نداشتند. نتایج نشان داد که همزیستی میکوریزی و باکتری ریزوبیوم به عنوان یک روش بیولوژیک و پایدار باعث ارتقای کیفیت ساختمان خاک شد.

    کلیدواژگان: کود بیولوژیک، کربن آلی، میانگین وزنی قطر خاکدانه ها
  • الهام یزدانی، وحید حسینی*، کیومرث محمدی سمانی صفحات 913-922

    آتش می تواند طیف گسترده ای از خصوصیات فیزیکی، شیمیایی، کانی شناسی و زیستی خاک را بسته به شدت خود تغییر دهد. هدف از انجام این پژوهش، بررسی و مقایسه اثر آتش بر ویژگی های شیمیایی خاک جنگلی در موقعیت های متفاوت در زیر گونه درخت بلوط ایرانی (برودار) (.Quercus brantii Lindl) در شهرستان مریوان بود. برای انجام این تحقیق، دامنه ای که در مرداد ماه سال 1396 آتش سوزی رخ داده بود، انتخاب شد. سپس ترانسکتی بر روی خطوط تراز به طول 250 متر پیاده شد و در فواصل 30 متری نزدیک ترین درخت برودار انتخاب شد و در نهایت دو نمونه خاک در عمق 5-0 سانتی متری و در دو فاصله نزدیک تنه (50 سانتی متری) و مرز تاج برداشت شد. در مجاورت این دامنه؛ منطقه شاهد انتخاب و به همین ترتیب عمل شد. در نهایت 32 نمونه خاک سوخته و نسوخته، برداشت و پس از انتقال به آزمایشگاه برخی ویژگی های شیمیایی شامل کربن، نیتروژن، فسفر، کلسیم، منیزیم، پتاسیم تبادلی، pH و EC اندازه گیری شد. نتایج نشان داد که با افزایش فاصله از تنه درخت، مقدار کربن و نیتروژن خاک افزایش یافت. فسفر، کلسیم، منیزیم و پتاسیم با حرکت به سمت مرز تاج درختان کاهش معنی داری داشتند. pH و هدایت الکتریکی نیز با افزایش فاصله از تنه درختان کاهش معنی داری داشتند. به طور کلی می توان گفت با حرکت از موقعیت نزدیک تنه به طرف مرز تاج خصوصیات خاک سوخته متفاوت بوده است که به دلیل تفاوت در مقدار مواد قابل اشتعال تجمع یافته، احتمالا شدت آتش کمتر شده و در نتیجه اثرات متفاوتی بر خاک گذاشته است.

    کلیدواژگان: تاج درخت، جنگل بلوط زاگرس شمالی، خاک جنگل، شدت آتش
  • طیبه شجاعی، غلامعباس فلاح قالهری*، عبدالرضا کاشکی صفحات 923-942

    با توجه به کمبود منابع آبی در کشور و دگرگونی اقلیمی، شناخت نواحی مستعد کشت درختان میوه براساس شرایط اقلیمی به منظور استفاده بهینه حائز اهمیت است. مطالعه حاضر با هدف توان سنجی شرایط اقلیمی ایران برای کشت درخت انگور کشمشی براساس تکنیک های چند معیاره و سامانه اطلاعات جغرافیایی بررسی شده است. در این راستا از آمار 200 ایستگاه هواشناسی عمده در سطح کشور در مقیاس های زمانی ساعتی، روزانه و ماهانه برای تعیین لایه های اطلاعاتی زیر معیارهای اقلیمی استفاده شد. آستانه های رشد و نمو درخت انگور براساس مطالعات کتابخانه ای مشخص شد. برای تعیین انباشت سرمایی مناطق مختلف کشور از مدل ساعات سرمایی CH استفاده شد. در ادامه با استفاده از فرآیند تحلیل سلسله مراتبی، معیارها و زیرمعیارهای اقلیمی لازم تعیین گردید. نتایج نشان داد که انباشت سرمایی دوره رکود که نیاز سرمایی را برطرف می کند، مهم ترین زیر معیار اقلیمی برای سنجش قابلیت های کشت درخت انگور محسوب می شود. همچنین در ایران 42195637.8 هکتار دارای قابلیت نامناسب و 42721336.2 دارای قابلیت ضعیف و 75492510 هکتار از قابلیت مناسب برای کشت انگور در گستره ایران برخوردار می باشد. مناطق مناسب کشت درخت انگور منطبق بر دامنه های مناطق کوهستانی و نسبتا مرتفع در نیمه غربی، شمال غرب، شمال شرق و مناطق پراکنده مرکز، شرق و جنوب شرق قرار دارد. محدوده مناسب کشت درختان انگور 42 درصد از سطح مساحت کشور را شامل می شود. نتایج و دستاوردهای مطالعه حاضر به عنوان الگویی برای کشت درختان خزان کننده سردسیر بر مبنای توان اقلیمی و جغرافیایی در جهت استفاده بهینه از منابع طبیعی حائز اهمیت می باشد.

    کلیدواژگان: ایران، توان سنجی، درخت انگور، شرایط اقلیمی
  • غزاله کواکبی، محمد موسوی بایگی*، امین علیزاده، ابوالفضل مساعدی، مهدی جباری نوغابی صفحات 943-958

    خشکسالی به عنوان پیچیده ترین، اما کمتر شناخته شده ترین خطر در میان تمام خطرات طبیعی است که نسبت به هر خطر طبیعی دیگر، درصد بیشتری از مردم را تحت تاثیر قرار می دهد. خشکسالی یکی از پدیده های طبیعی و مکرر اقلیمی است؛ تجزیه و تحلیل ریسک خشکسالی ترکیبی از تجزیه و تحلیل خطر خشکسالی و تجزیه و تحلیل آسیب پذیری خشکسالی است. در این مطالعه سعی شده است چشم انداری از تغییرات ریسک خشکسالی هواشناسی در آینده نشان داده شود. مطالعه به صورت موردی برای زیرحوضه افین (واقع در استان خراسان جنوبی) انجام شده است. دوره آماری استفاده شده برای دوره پایه 33 سال (2015-1983) می باشد. داده های آینده براساس سه مدل از پروژه CORDEX بدست آمده است. دوره آتی، به سه دوره 27 ساله شامل، آینده نزدیک (2046-2020)، آینده میانی (2073-2047) و آینده دور (2100-2074) تقسیم شده است. به منظور محاسبه ریسک خشکسالی، مخاطره خشکسالی براساس سه شاخص خشکسالی SPI، SPEI  و eRDI برای دوره پایه و دوره های آتی و پس از آن آسیب پذیری تعیین شد. افزایش شدت خشکسالی ها در دوره های آتی از دیگر نتایج حاصل از این مطالعه است. خروجی های ریسک بدست آمده از روش مستقیم محاسبه ریسک که با داده های CORDEX و نیز روش استفاده از مدل پیش بینی ریسک که در این مطالعه بدست آمد، نشان از افزایش تعداد وقایع خشکسالی و بدنبال آن افزایش وقایع ریسک خشکسالی در منطقه دارد. همچنین، مشاهده شد شدت ریسک خشکسالی ها براساس سناریوی انتشار RCP8.5 بیشتر از RCP4.5 می باشد

    کلیدواژگان: آسیب پذیری خشکسالی، ریسک خشکسالی، مخاطره خشکسالی، ARIMA، CORDEX
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  • m ahmadian, M. Montaseri Pages 795-809
    Introduction

    In recent decades, with increasing the world population and demand for fresh water for various applications (drinking, agriculture and industry), planning, management and optimal utilization of surface water reservoirs, especially in arid and semi-arid regions, have become the most serious challenges faced by researchers and water industry professionals in many parts of the world. In surface water reservoirs, uncontrolled flow is stored in wet periods for use in low flow periods. Therefore, surface water storage dams are created to control and regulate the flow of rivers in order to meet demand for different uses at a certain level of performance indices. During the process of storing water in the reservoirs, the uncontrolled flows of the input into the reservoir are in three ways: yield or output adjusted to meet demand for various uses, infiltration loss and evaporation from the surface of the lake and spill of excess water in a reservoir that is part of an uncontrollable flow. The proposed methods of storage-yield-performance of the storage system are classified into two main groups, simulation and optimization methods, which are widely used to analyze the reservoirs system for storing surface water. Among two final methods of simulation i.e. the behavior analysis method and the modified Sequent Peak Algorithm (SPA) method, all the actual conditions governing the system of storage reservoirs, including control of indices of reliability and vulnerability in the storage-yield-performance, are required to apply SPA. The basic SPA simulation method has been proposed as a computational method for the mass curve, and major improvements have been made to increase its functionality and efficiency at the late 20th century. The first amendments to apply the effects of evaporation losses and performance indices; time-based reliability and vulnerability, were carried out by Lele (1987). Then, Montaseri (1999) developed the SPA method for the system of multiple storage reservoirs and used non-linear or real area-volume relationship for applying losses caused by evaporation.

    Materials and Methods

    Stochastic models provide the possibility of generating successive hydrological time series (such as rainfall and flow) that are likely to occur in the future. On the other hand, the analysis of long-term behavior of various water resources systems, especially the storage system, depends on the availability of expected river flow time series in the years to come. Therefore, the use of stochastic models and the production of artificial data are absolutely necessary for the accurate evaluation of the design, operation and optimal management of the storage system and the elaboration of their long-term behavior. For this purpose, using a single distributed stochastic model, 1000 series of annual and monthly flows of input into the storage reservoir were generated and then the series of monthly flows generated to simulate the storage reservoir system using the SPA-I method and the reservoir performance indices (time reliability, resiliency and vulnerability) were also used for single reservoir system.

    Results and Discussion

    The results show that combining two stochastic AR(1) and Valencia-Schaake models had very good performance in preserving statistical data of historical data at two monthly and annual levels. This is the advantage and necessity of using the stochastic distributions model relative to other stochastic models such as Thomas-Fiering and ARMA in analyzing the storage reservoirs systems. The behavior of the reservoir system or the critical period in addition to demand, depends on system performance indices and decreases the critical period by decreasing time-based reliability or increasing the vulnerability factor. The results also indicate nonlinear (exponential) changes in the critical period and demand at a certain level of performance indices. Moreover, evaporation loss changes for demand and a certain level of performance indices have a concave shape, with a reversing point consistent with the largest within-year storage system. With a decrease/ an increase demand and volume of storage, the amount of evaporation losses increased exponentially and accounted for a considerable percentage of the reservoir's storage capacity.

    Conclusion

    The results revealed that volume of storage in addition to demand is a function of evapotranspiration losses and time-based reliability and vulnerability indices and follows an exponential relation for demand. In addition, in all three variants of the modified SPAs (SPA-I, SPA-II, and SPA-III), two performance indices of the reservoir, namely time-based reliability and vulnerability, are controllable in analysis, and the storage system analysis is performed for specified values or mentioned indices. Also, in the SPA-II and SPA-III methods, it is possible to use a nonlinear or a real are-volume relationship to estimate the loss of evapotranspiration in the storage system. Control of two performance indices of the reservoir and the application of real or nonlinear area-volume relationship in the analysis of reservoir system reservoir are important advantages of the above methods to the behavior analysis method.

    Keywords: Data generation, Lar reservoir dam, Reservoir simulation, SPA method, Stochastic model
  • Roghaieh Najafipour, Hadi Ramezani Etedali, Bijan Nazari Pages 811-822
    Introduction

    Greenhouses have a key role in agriculture productions. Given the ability of controlling production factors, there is the possibility of out-of-season cultivation in greenhouses, which is important in terms of food security, economics, and agricultural marketing. Estimation of water requirement for planning the development of greenhouses and their operation is very important. Awareness of the exact amount of water requirement is important both in terms of production and growth. Many studies have shown the usefulness of greenhouses in improving yield, physical and economical productivity. So far, comprehensive studies have not been carried out on the productivity of greenhouse cucumber cultivation and its effects on water resources in Qazvin province. Therefore, the goal of this study was to determine the greenhouse cucumber water requirement and provide a model for estimating evapotranspiration of cucumber under greenhouse condition. Also, determining greenhouse cucumber productivity in Qazvin province and evaluating the effect of this improvement on water resources were other objectives.

    Materials and Methods

    This research was carried out in a greenhouse near Qazvin city. The height of the greenhouse from the ground was 4 meters, and its plastic cover was made of polyethylene. Experiments were carried out in greenhouse with greenhouse seedling on 20-3-2015 in two rows of pot. The greenhouse was equipped with the necessary tools to measure temperature, maximum and minimum temperature, relative humidity, and solar radiation. Soil texture in this research was clay loam with 30, 32 and 38 percent of sand, silt and clay, respectively. The water content was, , 31% and 16 percent at field capacity (FC) and permanent wiling point (PWP) respectively. An irrigation interval of two days (a favorable condition) was considered. In this experiment, the seeds of the Royal cucumber were used to coincide with the planting time and harvesting length. The plastic pots with a diameter of 18 cm and a height of 23 cm were utilized. The pots were filled with equal quantities of fine and fine gravel (for drainage) and then with the agricultural soil prepared for cucumber cultivation. In order to provide conditions similar to the actual cucumber planting in the flower bed, the pots were placed close to the greenhouse. The irrigation of the plants was carried out manually for 83 days. The relative humidity, temperature and radiation were measured hourly. Further, the effects of irrigation on different characteristics of the test plants were observed and recorded. The moisture content was measured by weight and soil moisture reduction in full irrigation was compensated for the FC moisture content in each irrigation interval. Until 30 days after planting (Stages 4-6), the pots were irrigated with equal amounts. In order to evaluate the effects of deficit irrigation, four treatments were considered. These treatment were as follows: first treatment (FI): irrigation depth equal to 100% of the plant evapotranspiration with five replications, treatment (DI20): irrigation depth equal to 80% of the plant evapotranspiration with five replicates, treatment 3: (DI40) irrigation depth equal to 60% of the plant evapotranspiration with five replicates and the fourth treatment (DI60): irrigation depth equal to 40% of the plant evapotranspiration with five replications.

    Results and Discussion

    The maximum and minimum evapotranspiration was 8.7 and 1.06 mm/day in 61 and 13 days after transplanting, respectively. By investigation different mathematical models, the best models for estimation of cucumber evapotranspiration in greenhouse was the power model based temperature, humidity and height of crop with R2 of 0.86. The FAO-Penman-Monteith and Blaney-Criddle models exhibited the best and worst performance  with R2 of 0.42 and 0.24, respectively. The cucumber water productivities in greenhouses ranged from 9.23 to 22.44 Kilograms per cubic meter. This wide water productivity range shows the importance of management and operation in water productivity improvement in greenhouses.

    Conclusion

    Estimation of greenhouses cucumber water requirement and water productivity are very important. The best model for estimating cucumber evapotranspiration in greenhouse was the power model based on temperature, humidity and height of crop with R2 of 0.86. In this study, cucumber water productivity was estimated in Qazvin greenhouses. The results showed that cucumber water productivities ranged from 9.23 to 22.44 Kilograms per cubic meter. Consequently, 117 ha greenhouse is required for producing the present value of cucumber in the province. This option would save 15 millions of cubic meter water in this area. Development of greenhouses with regarding to various economic and social aspects can help decision-makers in solving water shortage problems.

    Keywords: Deficit irrigation, Evapotranspiration, Penman-Monteith
  • T. Raeisinejad, N. Yazdanpanah Pages 823-832
    Introduction

    Water has been known as an important limiting factor for plant growth and agricultural yields in arid and semi-arid regions. It is a significant input to agricultural production and also an essential requirement for domestic, industrial and municipal activities. Increasing population and standards of living are contributing to a steep rise in demand for fresh water. By using proper irrigation management practices in farmlands, it is possible to utilize water, soil and fertilizer to produce high yield and quality products. Drip irrigation is considered as one of the most efficient irrigation methods. One of its major advantages is the ability to apply water to the soil as often as desired and in smaller quantity than the other irrigation methods. Two systems of drip irrigation including surface and subsurface drip irrigation methods have been widely used in arid and semiarid regions to reduce the water deficiency impact. Subsurface drip irrigation has been used for many years because of its effectiveness in reducing soil surface evaporation. It has been widely used in horticultural crops under both greenhouse and outdoor field conditions. However, the surface drip irrigation system can be used easier than the subsurface drip irrigation system. In addition, deficit irrigation is one of the strategies for efficient use of water and increasing water use efficiency in agricultural district. Deficit irrigation is a suitable solution to gain acceptable and economic performance by using minimum amount of water. The aim of this study was to evaluate the yield and yield components of sunflower affected by different levels of soil matric potential in combination with two contrasting drip irrigation method i.e. surface and subsurface. In addition, water use efficiency as an important criterion of yield was used to achieve the best and more suitable irrigation method under water scarcity conditions.

    Materials and Methods

    In order to investigate the irrigation management of sunflower, a field experiment was carried out during 2016 growing season at an experimental farm in Jiroft city. The treatments were laid out in split strip plots based on randomized complete block design with three replications. The treatments were comprised of three soil matric potentials of 40, 55, and 70 centibar for initiation of irrigation in the main plot and sub plots consisted of two drip irrigation systems (surface and subsurface). In  the surface systems, drip lines were placed on the soil surface at a distance of 15 cm from the plant and in the subsurface systems, drip lines were placed at a depth of 30 cm. The irrigation time was determined based on the readings of metal tensiometers. These tensiometers were installed in three depths of 15, 30 and 50 cm of soil and at a distance of 20 cm from the plant. In this regard, in both irrigation systems, the mounted tensiometer at a depth of 15 cm of soil was used in the early growth and development, and mounted Tensiometers at depths of 30 and 50 cm soil were used in the middle and final stages of growth. In order to carry out irrigation at the potential point of view, the tensiometers were fully controlled and when the calibrated tensiometer screen showed the desired potential point, irrigation was carried out and the irrigation process continued until the soil moisture reached the crop capacity level. Yield, yield components such as number of seeds per head, along with water use efficiency were measured. Data were statistically analyzed using SAS Statistical software. Treatment means were compared using LSD test.

    Results and Discussion

    The results showed that the water usage parsimony of 153.6 mm (21.5 percent) between the 40 and 55 c-bar tensions caused that the yield, number of seeds per head and height of plant decreased by 12.5%, 12.8% and 11%, respectively, but water use efficiency increased 10.3%. Compared with 55 c-bar tention, 70 c-bar also decreased the yield, number of seeds per head and height of plant by 33.4%, 22.9% and 22.5%, respectively but increased water use efficiency by 4.7%. Moreover, the yield in subsurface drip irrigation increased by 499 kg/ha compared with surface irrigation. In addition, parsimony of water usage was 10% and water use efficiency increased by 21.5%. Number of seeds per head and the height of plant increased by 8.2% and 8.7%, respectively in subsurface drip irrigation.

    Conclusion

    According to the results of this study conducted on sunflower in Jirot area, it was concluded that the application of soil matric potential of 55 centibar in subsurface drip irrigation system is the best approach to increase water use efficiency during periods of drought.

    Keywords: Drought Stress, Drip Irrigation, Soil matric potential, Water use efficiency
  • marziyeh piri, Ebrahim Sepehr, A. samadi, Mohammad Alizadeh khaled abad Pages 833-844
    Introduction

    Some of the heavy metals such as cadmium (Cd) and lead (Pb) are toxic and represent hazardous pollutants due to their persistence in the environment. These metals have adverse effects on human health, which include growth retardation, cancer, damage to the nervous and heart system. Heavy metals can cause malfunctioning of the cellular processes via the displacement of essential metals from their respective sites. Mainly heavy metals discharge into the environment from industrial and urban sewage. There are different methods to reduce water pollution and the removal of heavy metals from water that one of them is sorption by using organic and inorganic adsorbents such as sepiolite. The low cost of sepiolite along with the high specific surface area, chemical and mechanical stability, and layered structure have made these clay minerals as excellent adsorbent materials for the removal of heavy metals from wastewaters. This study aims to investigate the sorption of Cd and Pb by sepiolite as an inorganic absorbent and optimize process variables (initial concentration, pH and ionic strength) using Response Surface Methodology (RSM) and Box–Behnken design (BBD).
     

    Materials and Methods

    Response Surface Methodology (RSM) is a statistical method that uses quantitative data from appropriate experiments to determine regression model equations and operating conditions. RSM is a collection of mathematical and statistical techniques for modeling and analysis of problems in which a response of interest is influenced by several variables. A standard RSM design called Box-Behnken Design (BBD) was applied in this work to study the variables for sorption of Cd and Pb by sepiolite from aqueous solution using a batch process. BBD for three variables (initial Cd and Pb concentrations, pH and ionic strength), each with two levels (the minimum and maximum), was used as an experimental design model. Sepiolite sample used in this study was taken from a mine in Fariman region, northeastern Iran. In the experimental design model, initial concentration (0-200 mg L-1), pH (3-6) and ionic strength (0.01-0.06 mol L-1) were taken as input variables. Design-Expert program was used for regression and graphical analysis of the data obtained. The optimum values of the selected variables were obtained by solving the regression equation and by analyzing the response surface contour plots. The variability independent variables were explained by the multiple coefficients of determination, R 2 and the model equation was used to predict the optimum value and subsequently to elucidate the interaction between the factors within the specified range.

    Results

    The results showed that the sorption of Cd and Pb intensified by increasing initial concentration and pH but ionic strength had an inverse effect. The sorption of Pb and Cd ions onto the sepiolite minerals were lowest at pH =3 and IS=0.06 but increased with an increase in pH and initial concentration of the solution. High value for R2 (0.99) and adjusted R2 (0.99) showed that the removal of Cd and Pb can be described by the response surface method. One-way ANOVA showed (p< 0.0001) that the quadratic model is the best model for determining the interaction variables. According to optimization results, the sorption of Cd and Pb are maximized when pH: 6, concentration: 200 mg.L-1 and ionic strength: 0.02 mol.L-1. The predicted adsorption at these settings for Pb and Cd are 44.4 and 34.28 mg.g-1, respectively. It was found that the initial concentration is the most effective parameter in the sorption of Cd and Pb by sepiolite. Sepiolite adsorbed more lead ions than cadmium ions from aqueous solution.

    Conclusion

    Response surface methodology using BBD, proved a very effective and time-saving model for studying the influence of process parameters (pH, initial concentration and ionic strength) on response factor (sorb). This model significantly reduces the number of experiments and hence facilitating the optimum conditions. The experimental values and the predicted values are in perfect match with an R2 value of 0.99. The high correlation coefficient between the model and experimental data (R2=0.99) showed that the model was able to predict the removal of Cd and Pb from aqueous solution by using sepiolite. The model revealed that concentration, metal type and pH were the most effective parameters on the response yield (adsorption by sepiolite), respectively. According to the results, sepiolite showed a greater efficiency for sorption of Cd and Pb from aqueous solution, also usage of sepiolite as an inorganic absorbent due to its low cost and abundance can be economically justified.

    Keywords: Box-Behnken design (BBD), Heavy metals, Sepiolite, Water pollution
  • Mohammad Ali Mahmoodi, Seyedeh Parya Naghshbandi Pages 845-856
    Introduction

    Soil erosion is a serious environmental threat leading to loss of nutrient from surface soil, increased runoff, lake and reservoir sedimentation, and water pollution. Thus, estimation of soil loss and identification of critical area for implementation of best management practice is central to success of soil conservation programs. Soil erosion modeling is an efficient method to simulate soil erosion, to identify sediment source areas, and to evaluate soil conservation measures. One of the most widely applied empirical models for assessing the sheet and rill erosion is the Universal Soil Loss Equation (USLE). Originally, USLE was developed mainly for soil erosion estimation in croplands or gently sloping topography. The RUSLE is an extension of the original USLE with improvements in determining the factors controlling erosion. It is an empirical model commonly used to estimate soil loss potential by water from hillslopes across large areas of land. RUSLE is a linear equation that estimates the annual soil loss as the product of environmental factors include rainfall, soil erodibility, slope length, slope steepness, cover management and conservation practices as inputs. To implement RUSLE over large areas, detailed sets of spatially explicit data are needed for precipitation, soil type, topographic slope, land cover and land use type. Conventionally, the collection of all these data from field studies is time-consuming and expensive. The integration of field data and data provided by remote sensing technologies through the use of geographic information systems (GIS) offers potential to estimate spatially input data for RUSLE over large and relatively sparsely sampled areas. Keeping in view of the above aspects, the objectives of the present study were 1) to integrate the field data and data provided by Landsat Enhanced Thematic Mapper (ETM) imagery with RUSLE through the use of GIS to estimate spatial distribution of soil erosion at Gawshan dam basin in west of Iran and 2) to delineate soil erosion probability zones by reclassifying of the prepared soil erosion map.

    Materials and Methods

    The annual rainfall erosivity factor (R) was determined from monthly rainfall data of 11 years (2005-2015) for 7 rain gauge stations in the the study area. Spatial distribution of R was estimated using ordinary kriging method of interpolation. The soil erodibility factor (K) was estimated on the basis of soil map prepared from land survey and Landsat ETM remote sensing data. The physical and chemical parameters required to calculate K were measured in the different soil units, and its spatial distribution was coincident with the soil unit boundaries. The topographic factor (LS) was derived from digital elevation model (DEM) of 30 m resolution. The annual crop management factor (C) was calculated from normalized difference vegetation index (NDVI) derived from Landsat ETM imagery for different seasons. Since there is a lack of field data regarding the conservation practices that have been taken place in the study area, the conservation support practice factor (P) value was taken as 1. Finally, average annual soil loss was estimated as the product of the mentioned factors, and categorized into four classes viz., low, moderate, high and very high erosion.

    Results and Discussion

    The estimated R, K, LS and C range from 564 to 1311 MJ mm ha-1 h-1 y-1, 0.02 to 0.04 t h MJ-1 mm-1, 0 to 2436 and 0 to 1, respectively. The results indicate the estimated mean annual potential soil loss of about 2.35 t ha-1, however in the 50% of the basin area annual soil loss is lower than 0.92 t ha-1. Based on categorized soil erosion map about nearly 52.5% of the basin area produces low erosion of 0.43 t ha-1 annually, whereas very high probability zone covers about 4% of the basin area, located dominantly in the southwestern part of the basin. Our results showed that slope steepness factor is the most important factor that controls soil erosion rate in the basin.

    Conclusion

    This study demonstrates the integration of field data and Landsat ETM imagery data with RUSLE through the use of GIS to estimate spatial distribution of soil erosion in Gawshan dam basin. The results of this study can be helpful for identifying critical areas for implementation of conservation practice and provide options to policy makers for prioritization of different regions of the basin for treatment.

    Keywords: Gawshan dam basin, Remote sensing, RUSLE, Soil erosion
  • Ajdar Onnabi Milani, Mohammad Zarrinbal Pages 857-871
    Introduction

    Almond (Prunus dulcis) has an important role in the agricultural economy of north-west of Iran, especially Azerbaijan provinces. Due to arid and semi-arid conditions of our country, large areas of cultivated land are affected by salinity. Almond trees have good tolerance to water stress, and are suitable for such conditions. However, sensitivity of almond trees to salinity calls for special attention to the integrated effect of salinity and water stress on its water relations. This trial aimed to evaluate the combined effect of salinity and drought stress on water uptake, vegetative growth and leaf water potential (LWP) of almond trees.

    Materials and Methods

    The experiment was conducted at the Sahand Horticultural Station located in East Azerbaijan, Iran (37o 55' 43'' N, 45o 57' 29'' E) during 2014 growing season at 7 years old almond (cv Azar) trees grafted on GF677 rootstock based on randomized complete block design with three replications. Treatments comprised three irrigation salinity levels viz. 2 (T1), 4 (T2), and 5 (T3) dSm-1. The soil of the experiment site was coarse loamy mixed calcareous mesic typic xerofluvents. Undisturbed and composite disturbed soil samples were taken from three diagnostic layers. Twelve undisturbed core samples were taken from each layer. Composite disturbed soil samples were air-dried and ground to pass a 2-mm sieve.  All the appropriate soil chemical (Organic matter and Calcium carbonate content, pH and EC, Total N, Available P and K) and physical (Particle size distribution, natural bulk density) properties were measured by the routine laboratory methods. Water contents at field capacity (FC) and permanent wilting point (PWP) were determined by the pressure plate apparatus. After irrigation of all trees with 200 mm water enough for saturating of soil in rooting depth on 20th of May, the measurements began. The volumetric soil water content (SWC) was measured at three locations around each tree 30 cm apart from tree trunk at three depths (0‒20, 0‒40 and 0‒70) using a TDR probe. During the experiment (20th May till 17th October), air temperature and relative humidity were obtained from the meteorological site located in the station. The midday leaf water potential (LWP) was measured from the leaves located in north part of trees close to stem between 12 and 14 o’clock.

    Result and Discussion

    Results indicated that salinity has significant effect (p<0.01) on LWP, vegetative growth and remaining water content. The difference between T3 and other treatments was not significant in SWC more than 8%. Therefore, it is obvious that, at SWC less than 8%, reduction in soil water potential due to increased osmotic pressure of soil solution in T3 have caused that, trees unable to uptake more water. Therefore, at SWCs less than 8%, remaining water content in T3 was significantly more than other treatments. Seasonal averages of annual vegetative growth and increase in trunk diameter in unstressed tree was 104 cm and 53%, respectively and decreased to 62 cm and 18% in T3 respectively. Seasonal averages of LWP for treatment T1 to T3 were ˗1.78, ˗1.93 and ˗2.16 MPa respectively. Whereas unstressed trees had highest LWP (-1.53 MPa). Highest and lowest LWP for treatment T1 to T3 were -1.20, -1.32 and -1.35 and -2.38, -2.47 and -2.73 MPa respectively. LWP of unstressed trees was between -1.1 and -2.0 MPa. There was significant negative correlation between LWP and VPD. The slope of regression equation increased as stress severity increased. This means that, for a given VPD, leaf water potential was declined with increase in salinity of irrigation water. LWP is affected by two stresses namely evaporative demand of the atmosphere (atmospheric-induced stress) and unavailability of water due to the reduction of soil water content (soil-induced stress). In well-watered plants, LWP is affected only by atmospheric factors (VPD) and therefore the relationship between LWP and SWC should not be significant as it took place in our experiment for unstressed trees. But there was a significant relationship between LWP and SWC in stressed treatments (T1 to T3) because of soil-induced stress. Threshold value of LWP for initiating stress was obtained to be -1.78 MPa. Based on the threshold LWP, values of SWC for initiating stress for treatment T1 to T3 can be 10.1, 11.8 and 13.5%, respectively.

    Conclusion

    Based on our findings, the midday leaf water potential is a suitable criterion for determining water status of almond trees in the studied area and can be used as an indicator for tree water and salinity stresses. Irrigation water salinity had significant effect on LWP. Due to relationship between LWP and soil water content (SWC), this indicator can be used for determination of soil available water and non-limiting water range of almond trees. Besides LWP, salinity also had a significant effect on vegetative growth and extractable soil water content. At high water content, the effect of salinity on extractable water content was not significant. But with decreasing water content, the effect of salinity increased so that, at SWC less than about 8%, the remaining SWC in saline condition was significantly higher than non-saline condition (extractable water in the saline condition was less than non-saline condition). Salinity also reduced soil available water range of almond trees., LWP reached to its threshold value (-1.78 MPa) at SWC equal to 10 and 13.5% in non-saline and saline condition respectively.

    Keywords: Soil water content, Stem water potential, Trunk diameter, Vapor pressure deficit
  • Ameneh Jahandideh, Esmael Dordipour, Reza Ghorbani Nasrabadi Pages 873-884
    Introduction

    One of the most important needs in the farm planning is the evaluation of different systems of plant nutrition. By supplying the correct way of plant nutrition, one can preserve the environment and increase the efficiency of agricultural inputs. Humic acid contains many nutrients that increase soil fertility, soil organic matter content, and access to macro- and micro-nutrients by preventing the formation of insoluble salts and chelating properties. Phosphorus and humic acid stimulate vegetative growth, improve reproductive growth, and increase the quantitative and qualitative yield of plants. In this regard, the positive effects depend on the amount and how they are applied. The present study was conducted with the aim of investigating the effects of different levels of humic acid and phosphorus fertilizer on phosphorus availability and photosynthetic pigments (a, b and carotenoids) in canola (cv. Hyola 50).
    Methods and Materials: The soil used in this study was collected from 0-30 cm layer of a soil profile passed through a 2-mm sieve after air-drying. The soil chemical and physical properties were then determined. The pot experiment was conducted as factorial based on completely randomized design with three replications. Treatments include phosphorous fertilizer as super phosphate in three levels (0, 50 and 100 mg/kg) and humic acid in three levels (0. 0.5 and 1 gr/kg soil), phosphorous and humic acid application ways. Humic acid and phosphorous treatments were mixed in various forms including simultaneous mixing of humic acid and phosphorous fertilizer in the soil matrix, application of humic acid and phosphorous via irrigation water and coting of phosphorous fertilizer via solid humic acid before soil application. Then 10 canola seeds were planted in each pot at 2-cm depth which were declined to 4 plants in each pot after emerging and greening phases. At the end of the growth period (158 days), the plants were harvested. Determination of phosphorus concentrations of plant extracts by molybdenum vanadate or yellow method and chlorophyll content (a, b and ab) and carotenoids were measured precisely before harvesting using Barnes method. After harvesting the plants, the soil was immediately air-dried and passed through a 2mm sieve. Then, the amount of phosphorus was determined by sodium-DTPA and sodium bicarbonate. The statistical results of the data were analyzed using SAS software and LSD test (at 5% level) was used for comparing the mean values.

    Results and Discussion

    The interactions of humic acid and phosphorus and its application methods were significant for all measured traits at the 5% level. The results of the triple effects of humic acid levels and its application at the presence of phosphorus treatments showed that the highest chlorophyll (a, b and ab) and carotenoid content was obtained at 100 mg/kg phosphorus and 1 g/kg humic acid along with irrigation water. The highest concentration of plant shoot phosphorus with an average of 0.30% was observed in 1 g/kg humic acid with irrigation water at the level of 100 mg/kg phosphorus, although had no significant difference with 0.5 g/kg of humic acid with irrigation water. Maximum amount of P was extracted by Olsen method with the mean of 16.14 mg/kg and Soltanpour and Schwab method with the mean of 5.24 mg/kg obtained in 100 mg/kg phosphorus and 1 g/kg soil humic acid application. There was a significant correlation between the phosphorus extracted by Olsen method and Soltanpour and Schwab method (r = 0.95), which was significantly correlated with concentration of phosphorus (r = 0.84) and (r = 0.85) (P<0.05). There was also a significant correlation between fresh and dry above-ground biomass, types of chlorophyll (a, b and ab) and carotenoids with phosphorus extracted by Olsen and Soltanpour and Schwab methods at 5% significance level.

    Conclusion

    P adsorption capacity is a function of many factors. Application of phosphorous fertilizers in calcareous soils, due to the presence of calcium with high activity, results in the formation of calcium phosphates, which becomes insoluble, over time. Humic material in interaction with phosphorus in the soil can reduce phosphorus stabilization and increase plant available phosphorus. The results of this study showed that the use of phosphorus with humic acid, rather than the use of phosphorus alone, could increase the available phosphorus in the soil and also the phosphorus concentration within the plant.

    Keywords: Carotenoid, Chlorophyll, Fresh, Dry Weight, Shoots
  • L. Ghorbaniminaei, M. Zakerinia, A. Rezaeiasl, H.R. Mirkarimi Pages 885-896
    Introduction

    Due to limited water resources in the country, the use of new methods of irrigation with low water consumption seems necessary. Subsurface irrigation is one of the few methods to increase crop water productivity. Also, in order to cope with the water crisis, unconventional water can be used, in other words, poor water quality is being applied. There are several methods for improving the quality of water in the agriculture section, one of which is the use of magnetic fields. The purpose of this study was to investigate the effect of groundwater table management on reducing water consumption and to investigate the possibility of sub-irrigation (drainage controlled) with magnetized wastewater of Gorgan urban refinery on rice yield.

    Materials and Methods

    This study was conducted from May to September of 2018 in Gorgan Agricultural and Natural Resources University. The experiments were carried out in a lysimeter with a diameter of 30cm and a height of 50cm. The experiment was conducted as a factorial based on randomized complete block design with three replications. Treatments included water type factor (ordinary water (C) and sewage (W)) and water correction factor (magnetic (M) and non-magnetic (O)). To control the water level, two water tanks were used, one as a stabilizer water table and another to measure the amount of water used. Part of the ordinary water and wastewater was magnetized using a DC magnetic field generator with magnetic one tesla field intensity. Underground irrigation was then carried out on the soil columns in which the rice plant was cultivated so that the water table depth was fixed at 5 cm from the soil surface. The lysimeters were irrigated with ordinary water for one week, in the second week of treatments were applied. At the end of the growing season, traits such as rice husk yield, biological yield, harvest index, water use efficiency, physical water productivity and economic water productivity were determined. The measured data were analyzed using SPSS. Also, comparisons of means were performed by using the t-test and Duncan tests at 5% level of probability.

    Results and Discussion

    The results of the comparison mean water type factor showed that there was no significant difference between the wastewater and the normal water in the parameters of the measurements. Correction Water showed that non-magnetic water was significant in rough rice yield, water use efficiency, water physical productivity, and water economic efficiency compared to magnetite, but on biological yield and harvest index had not a meaningful effect. Also, the comparison of the mean of water type and correction water method on all measured parameters indicated that the nonmagnetic wastewater was superior to the rest of the treatments at the 5% level.

    Conclusion

    This study was conducted to investigate and further study two methods of controlled drainage management and underground irrigation for rice cultivation with the Gorgan municipal wastewater treatment plant. Based on the results of the comparison of mean interaction effects of treatment compounds, non-magnetic effluent was identified as the best treatment composition in this experiment. According to the results of this research, we can say:  Rice cultivation in terms of irrigation does not require the formation of a standing water layer on the surface of the soil. Also, by using wastewater of Gorgan urban refinery for irrigation water, in addition to reducing the harvesting of high-quality water resources, the cost of fertilizer use (chemical and organic) in the production of crops can be reduced. Overall, the results of this study showed that the magnetic factor had no effect on the improvement of rough rice yield, water use efficiency, physical productivity water and economic efficiency of water under underground irrigation conditions. However, it should be noted that the results of this research are only It is obtained by a magnetic device model. Therefore, it is possible that the use of different models of magnetic devices results in different results. It is also probable that the passage of irrigation water with different compositions (percentage of cations and various anions) from the magnetometer can lead to different results on other crops or cultivars of a crop.

    Keywords: Controlled drainage, Magnetism wastewater, Rice yield, Sub-irrigation, Urban wastewater treatment
  • Ladan Heydari, Javad Hamzei, Tahmeineh Ghytasi Ranjbar, Somayeh Bahramian Ragheb, Fatemeh Madineh Khorrami Pages 897-911
    Introduction

    Stability of soil aggregates is a result of complex physical, chemical and biological processes in the soil. In many studies, organic matter has been studied as a major factor in formation of aggregates and the effects of symbiosis between mycorrhizal fungi and bacteria largely ignored, however these microorganisms have a great effect in the formation of the aggregates. Plant roots provide a suitable habitat for the activity of many soil microorganisms. In this regard, the symbiosis of plant roots with fungi is one of the most common and long-lived symbiotic relationships that are found in most ecosystems. On the other hand, biological fertilizers can improve soil aggregation through influence the growth of root and plant. Despite the significant effect of fungi and bacteria on the stability of the soil structure, the effect of arbuscular mycorrhizal fungi species Glomus mosseae and Rhizobium species Mesorhizobiumon caesar on the soil structure has been rarely investigated. Therefore, the aim of this study was to evaluate the effect of chickpea inoculation with Rhizobium (Mesorhizobium caesar) and mycorrhizae (Glomus mosseae) on soil structural stability and aggregates size distribution under both greenhouse and field conditions.

    Materials and Methods

    The present study was conducted as a randomized complete-block design with three replications in both greenhouse and field conditions. The treatments under field condition were mycorrhizal fungus (Glomus mosseae), Rhizobium (Mesorhizobium caesar), mycorrhizae – rhizobium combined treatment and a control (no inoculation). In the greenhouse condition, sterilized mycorrhiza background material and without plant (without inoculation) treatments were also added. Chickpea was planted at both conditions. Soil sampling was carried out after harvesting. The stability of aggregates using wet sieving method and soil organic carbon content were investigated.

    Results and Discussion

    Greenhouse study results showed that mycorrhizae treatment significantly increased the mean weight diameter of the aggregates by 51.6% and 189.1%, in comparison with the control (without inoculation) and control- without plant (without inoculation), respectively. This treatment increased macro aggregates and decreased the fine aggregates. In the greenhouse condition, soil organic carbon content had a high correlation with the mean weight diameter of the aggregates (R2 = 0.53) and mycorrhizal treatment increased organic carbon content from 0.73% in the control (without plant) to 1.02%. However, the mycorrhizae – rhizobium combined treatment had less effect on the stability of the aggregates than their single effects. The mass of aggregates of 1–2 mm are more sensitive to short-term management. In the greenhouse condition all the three biofertilizer treatments significantly increased the mass of the aggregates of 1-2 mm in comparison with the control treatment without plant (without inoculation). On the other hand, the mean comparison results showed that there was no significant difference between the sterilized mycorrhizal background and the control without plant (without inoculation). This may be due to the lower organic matter content in these two treatments compared to others. In the greenhouse condition, increasing the mass of coarse aggregates of 4-8 mm in diameter indicates the suitability of soil structure. On the other hand, aggregates coarser than 0.25 mm are considered as coarse and stable aggregates. It can be concluded that the application of mycorrhiza and rhizobium increased soil structural stability through the increase of the mass of these classes of the aggregates (2-4 and 4-8 mm), probably by affecting the length and volume of the root and plant yield. Under the field condition, the treatments had no impact on the mass of the aggregates in different size classes.

    Conclusion

    Bacteria and fungi can be effective factors in improving soil structure through increasing organic carbon in soil. The results of the present study indicated that aggregate stability was affected by biological fertilizer treatments under greenhouse condition so that the treatments containing biofertilizers increased soil aggregate stability and improved the soil structure that was probably due to increasing plant yield and root. Also, the less effect of biofertilizers on the stability of the aggregates and the increase of coarse aggregates under the field condition can be due to the uncontrolled climatic conditions compared to the greenhouse and the short duration of the study. In recent decades, the physical and chemical properties of soils have changed due to the use of chemical inputs in agricultural lands.The use of biological and organic fertilizers is an appropriate solution to these problems. It is recommended further study on the efficacy of other species of mycorrhizal fungi and rhizobium bacteria in improving soil physical and chemical quality, especially at the field scale. Also, considering the implementation of this project in the field condition, it is suggested to study the physical, mechanical and chemical properties of soil in the long term.

    Keywords: Biofertilizer, Mean weight diameter, Organic carbon
  • Elham Yazadni, Vahid Hosseini, Kyumars Mohammadi Samani Pages 913-922
    Introduction

    Fires are natural processes in many ecosystems, constituting a natural, even vital, component of forests. Fire can change the soil properties depending on its severity. In semi-arid regions, the effects of fire are more vigorous in comparison with other regions. In these regions, forests restoration is much more difficult especially in the summer when temperatures reach maximum levels and cause fires that reduce soil nutrients by burning organic matters and vegetation. Since the frequency of fire events in Zagros oak forests have been increasing in recent years, therefore, in this study, the chemical properties of soil investigated immediately after fire. Most wildfires in these forests are surface fires with low-to-moderate severity due to low forest density, great distances between trees and few forest floor plants.

    Materials and Methods

    The study area is located in Kurdistan Province, western Iran, around Marivan that has been burned in July 2017. One transect was installed on the contour line with 250 m length on the burnt slope. Eight Persian oak trees were selected at 30 meters interval. Two soil samples were collected in each tree from depth of 0-5 cm. The two positions of soil samples including: the first one was 50 cm far from the base trunk and the second one was on the edge of tree crown border. In the control area, eight Persian oak were selected in the adjacent area of burned area with same topographic and plant conditions and soil samples were collected same as burned area. Finally, soil organic carbon (SOC), Total nitrogen (TN), available phosphorus, potassium, calcium, magnesium, pH, and EC were analyzed.

    Results and Discussion

    The results of this study showed that fire has a significant effect on soil properties, so that organic carbon reduced and amount of available phosphorus, calcium, magnesium and potassium of soil increased in burned soil. Organic carbon decreased significantly (P<0.01) in the burned soil in comparison to control treatment near tree trunk while it did not have any significant difference in the border of tree crown. The lowest Organic carbon was 6.19% in burned soil near tree trunk and the highest 9.15% in unburned soil in the border of tree crown. Total nitrogen did not show any significant difference between all treatments. Phosphorus increased significantly after the fire in the burned soil by comparison with control in the both positions. The increase of available P in soil after fire can be due to added ash as the fire partially and completely combusted plant debris in the soil. The highest phosphorus was 130.08 mg/kg in the burned soil near tree trunk and the lowest was 65.67 mg/kg in soil of control area in the border of tree crown. Cations including Ca, Mg and K were significantly higher near tree trunks in burned soil compared with control area, while only Ca and Mg of soil showed significant differences in the border crown position. The pH of burned soil was 7.62 and 7.05 near tree trunk and border of tree crown, respectively, and it was 7.15 and 6.89 near tree trunk and border of tree crown, respectively, in control area. The EC of burned soil was 1.70 mS/cm and 0.66 mS/cm near tree trunk and border of tree crown, respectively and it was 0.44 mS/cm and 0.54 mS/cm near tree trunk and border of tree crown, respectively in control area. One-way ANOVA showed that two positions of soil samples had significant effect on all soil parameters except nitrogen. In the Zagros oak forests, there are a lot of flammable materials inside stands, which can lead to low and medium intensity fire .According to the results of this study, the amount of organic carbon of burned soil near tree trunk was less than the crown border because of high accumulation of flammable materials and high fire intensity.      

    Conclusion

    In general, it can be concluded that wildfire causes significant changes in chemical properties of forest soils. Changes in the chemical properties of soil between burned soil and control area differed with movement from tree trunk to border of tree crown, so that the amounts of phosphorus, potassium, magnesium, calcium, acidity and electrical conductivity were reduced and the amount of carbon increased. Hence, it seems that properties of soil burned has diffiered by moving from the tree trunk to the border of crown trees probabley because of the differences in the amount of accumulated litter, consequently has an effect on the characteristics of the soil in different postions.

    Keywords: Forest soil, northern Zagros oak forest, tree crown, wildfire severity
  • Tayebeh Shojaee, Gholamabbas Fallah Ghalhari Pages 923-942
    Introduction

    In order to choose the best forms for each region and invest, the climatic conditions should be considered. Among the climatic elements, thermal indexes are effective factors in the production cycle, and the quality and quantity of grapes. Given the lack of water resources and the threat of climate change, there is a need for potentiometry and clustering of different regions.

    Materials and Methods

    According to the content and purpose of statistics and information, the hourly and daily climatic data of 200 climate stations were used. In order to compute the required chilling, the CH model was prepared and implemented. According to daily and monthly statistics, climate parameters were refined and investigated. We used a weighting method based on hierarchical approach for accurate decision making and identifying the relative importance of climatic criteria for grape cultivation. For the following climatic criteria, the information layer was arranged through a database of 200 meteorological stations of the Iranian Meteorological Organization. For the following geographic criteria, layers were used in the country. In order to determine the suitable areas for planting grapevine, using the Analytical Hierarchy Process (AHP) method in the Epert choice11 software environment, the criteria and sub criteria were weighted. Then, using the Geographical Information System, the layers were overlapped based on their weight and the final land suitability map for planting grapevine in Iran was obtained based on climatic conditions.

    Results and Discussion

    Pairwise comparison of criteria and sub-criteria based on hierarchical analysis showed that the criterion of climatic conditions with a weight of 0.63 was considered as the most important criterion in determining suitable areas for grapevine cultivation. Pairwise comparison of the climatic conditions criterion indicated that the sub-criteria of 451 were the highest among the sub-criteria in the grape trees. Temperature sub-criteria exhibited the greatest weight during the slump and growth period. Paired comparison and spatial distribution of the climate-chilling showed that a large part of the country does not supply winter creeps or cold storage for grapevine trees. The southern half of Iran is entirely unsuitable due to the existence of mild winters for commercial cultivation of creeping trees such as grapes. Paired comparison and spatial distribution under the climatic criterion of the slump period demonstrated that largest spatial distribution is allocated to the middle class in the margin of highlands and high latitudes regions. Paired comparison and spatial distributions under the scale of the growth period illustrated that the spatial pattern in this sub-criteria is highly dependent on the altitude and latitude. From the north to the south and from the west to the east, the suitability for growing grapevine decreases. Paired comparison and spatial distributions under the climatic criteria of absolute minimum temperature revealed that in terms of absolute minimum temperature, there is a limitation on grapevine for some regions of Iran. These areas are mainly mountainous belts of the Zagros mountain, the northwest cold region and northeastern Iran. Paired comparison and spatial distribution under the climate criteria of maximum air temperature showed that temperatures above the threshold of 40 degrees Celsius adversely influence the quality and yield of grapevine. In fact, in terms of absolute maximum temperatures, more than half of the country's surface area is unsuitable. Paired comparison and spatial distributions under the geographic scale elevation above sea level showed that suitable altitude areas are limited to the high and mountainous regions of the northwestern, northern, and northeastern Iran. Paired comparison and spatial distributions under the relative climate of relative humidity indicated that due to the relative humidity of the grape vine compared to many fruit trees, the relative humidity in Iran is high for the grapevine tree. Paired comparison and spatial distributions under the climatic criteria of sunshine hours illustrated that the distribution of sunshine hours affects the latitude factor causing an increase in sunshine hours from north to south. A wide range of  growing fruit trees in terms of sunshine days can be found in Iran. Therefore, most regions in the country provide unlimited solar radiation for grapevine growth. Paired comparison and spatial distributions under the geographic scale elevation above sea level showed that altitude plays an important role for locating vineyards. Suitable high-altitude areas are limited to the high and mountainous regions of the northwestern, northern, and northeastern Iran. Paired comparison and spatial distribution below the gradient geographic scale showed that planting fruit trees, especially grapes, is more cost-effective in steep slopes. Considering the high adaptability and physiological conditions of the grapevine, almost all regions of Iran, except very high and mountainous regions, are suitable for planting grapes. Suitable vineyard cultivars are adapted to the slopes of mountainous and relatively high mountainous regions in the mid-west, northwest, northeast, and scattered areas of the center, east and south east of the country. The range of cultivating grapevine trees is 42% of the country's surface area.   

    Conclusion

    The results revealed that the climate criterion has a pivotal role for determining land suitability for grapevine trees. The suitable vineyard cultivars are located in the mountainous and relatively hilly mountains in the northwest, northwest, northeast, and dispersed areas of the center, east and south east of Iran. These findings are important for land use planning and spatial planning with emphasis on climatic and geographic capabilities for efficient use of natural resources.

    Keywords: Climatic condition, Grapevine, Land suitability
  • Mohammad Mousavi Baygi, Amin Alizadeh, Aboalfazl Mosaedi, Mahdi Jabbari Noghabi Pages 943-958
    Introduction

    Drought is the most complex, but less well-known risk among all natural hazards, which affects more people than any other natural hazard. Meteorological and seasonal hydrological drought is a common phenomenon in tropical countries and is expected to increase further in the future. Drought is one of the natural and frequent climate phenomena; Drought risk analysis is a combination of drought risk analysis and drought vulnerability analysis. Drought risk assessment methods can be calculated either by remote sensing methods or by statistical methods or by combining both methods. Drought risk assessment shows a more Suitable and accurate view of the drought because, in addition to drought severity  is  simultaneously Includes the probability of occurrence of drought and the impact this phenomenon on the environment and the region. In this study, has been made to illustrate Visionary of Changes in future meteorological drought risk.

    Materials and methods

    The study was conducted as a case study for the Afin sub-basin The average of minimum temperature, mean of maximum temperature, average temperature at 2 meters above ground level and rainfall data in this research have been used. The statistical period used for the base period is 33 years (1983-2015). Future data is derived from three models of the cordex project. The upcoming period is divided into three 27-year periods including the near future (2020-2046), the middle term (2047-2073) and the distant future (2074-2100). In order to investigate the drought in future periods was prepared a combination model of three climatic models  using the Bayesian method. Then, the future values of the meteorological parameters were calculated. Drought risk for the upcoming periods was calculated by direct method and modeling method. Finally, a comparison was made between the two methods in order to determine the appropriateness of the predicted model.

    Results and discussion

    In the survey of the intensity of SPI and SPEI drought indices during the base time period for time scales studied, the SPEI and SPI drought indices showed that both, drought events were the same during the studied period, while the indicator SPEI drought shows more mild and moderate droughts, and the SPI index has shown intense intensity on some scales. In future periods, according to the RCP8.5 scenario, the number of  drought events  in each period does not differ from the RCP4.5 scenario, but the intensities are higher than RCP4.5. By completing the questionnaire and using exploratory and confirmatory factor analysis methods, the drought vulnerability was determinated 53%. ARIMA (0,0,0) , The appropriate time series model was used to predict the level of risk. In the drought risk prediction section, the results showed that according to the SPI drought index in the upcoming periods, the number of drought events relative to the base period is relatively higher, thus the number of drought events (including four drought conditions) will increase in the far future than the two upcoming middle and nearer periods. According to prediction models of risk, rainfall parameter  for all time scales of SPI index and for four time scales of spring, autumn, winter and annual drought index SPEI,  is an effective parameter in drought estimation and effect on drought occurrence in the study area.

    Conclusion

    The results of this study indicate an increase in temperature in future periods based on both RCP emission scenarios. Increasing the severity of droughts in future periods is another result of this study. The risk outcomes obtained from the direct risk-measurement method, which was obtained with CORDEX data as well as the method of using the risk-predictive model obtained in this study,Showed strong correlation and no significant difference in mean, which indicates the model's appropriateness for risk prediction (hazard and after that risk) in the future.Also,The risk outcomes obtained from the direct Risk calculation method, which is based on CORDEX data with the method of using the risk prediction model obtained in this study, indicates an increase in the number of drought events followed by an increase in drought risk events in the region. also, it was observed that Severity of drought risk according to the RCP8.5 release scenario is higher than RCP4.5. For more more accurate results, it is suggested that more models (more than three models) be used from the sixth report of the Intergovernmental Panel on Climate Change.

    Keywords: Drought Vulnerability, Drought Risk, Drought Risk ARIMA, ARIMA, CORDEX