فهرست مطالب

مهندسی زراعی - سال چهل و دوم شماره 1 (بهار 1398)
  • سال چهل و دوم شماره 1 (بهار 1398)
  • تاریخ انتشار: 1398/03/13
  • تعداد عناوین: 10
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  • سحر اخوان، سهیلا ابراهیمی*، مریم نوابیان، محمود شعبان پور، سید علی رضا موحدی نائینی، علی مجتهدی صفحات 1-12

    ماکروپورهای خاک مهم ترین عامل انتقال پساب کودها و میکروارگانیسم ها از جمله باکتری های شاخص مدفوعی به خاک های عمیق تر و حتی به آب های زیرزمینی می باشند. در این راستا، پژوهش حاضر با هدف مطالعه ترابری ترجیحی و نگهداشت باکتری اشرشیاکولای به عنوان یک باکتری شاخص و متداول در کودهای حیوانی در شرایط استفاده از آب شور تعریف گردید. مطالعات آزمایشگاهی در سیستم جریان ترجیحی با ماکروپورهای مصنوعی با قطرهای مختلف (1 و 2 سانتی متر) و تیمار شوری مختلف آب (1، 2 و 4 دسی زیمنس بر متر) تحت جریان اشباع در سال 1395 انجام شد. طرح آماری مورد استفاده، فاکتوریل دو فاکتوره در قالب طرح کاملا تصادفی بود. نتایج نشان داد که اثر متقابل شوری و قطر ماکروپور بر میانگین غلظت خروجی(Cav)، ضریب پالایش باکتری (fλ)، شاخص نسبی جذب باکتری (SR) و عمق بیشینه پیش بینی شده انتقال باکتری (Zmax) در سطح آماری پنج درصد معنی دار بود. تیمار شوری 4 دسی زیمنس بر متر و بدون قطر ماکروپور بیشترین مقدار پالایش (01/0 کلنی بر میلی لیتر) را نشان دادند، به طوری که با افزایش قدرت یونی به میزان 2 برابر، از میزان پالایش 30 درصد کاسته شد. به طور کلی نتایج نشان داد که عامل اصلی انتقال باکتری وجود جریان ترجیحی در اثر پیوستگی ماکروپور است، اما شوری به عنوان یک عامل بازدارنده با افزایش قدرت یونی محلول خاک، میزان پالایش باکتری را کاهش داد.

    کلیدواژگان: پالایش باکتری، جریان ترجیحی شاخص جذب باکتری، ماتریکس، ماکروپور، شوری
  • نرجس سوسرائی، مجتبی بارانی مطلق*، فرهاد خرمالی، اسماعیل دردی پور صفحات 13-31

    زغال زیستی، مواد آلی مقاوم به تجزیه بوده و حاصل حرارت دهی زیست توده های گیاهی و بقایای کشاورزی در شرایط عدم وجود اکسیژن یا اکسیژن محدود می باشد. به منظور بررسی تاثیر زغال زیستی حاصل از بقایای کشاورزی (برنج، پنبه و کلزا) بر ویژگی های رشد رویشی و شاخص سبزینگی و انواع کلروفیل گیاه ذرت، آزمایشی به صورت فاکتوریل در قالب طرح کاملا تصادفی در 4 تکرار به اجرا درآمد که تیمارها شامل شاهد و 3 نوع زغال زیستی تهیه شده از بقایای برنج، پنبه و کلزا در دماهای 350 و 700 درجه سلسیوس هرکدام با مقادیر 2 و 5% وزنی بودند. نتایج نشان داد که در اثر تبدیل بقایای کشاورزی به زغال زیستی مقادیر pH، قابلیت هدایت الکتریکی و محتوی خاکستر افزایش و مقادیر کربن آلی و بازده زغال زیستی کاهش یافت. همچنین افزایش دمای تولید زغال زیستی از 350 به 700 درجه سلسیوس منجر به تولید زغال های زیستی با pH و قابلیت هدایت الکتریکی بالاتر شد. نتایج نشان داد که اثر زغال های زیستی و سطح کاربرد بر تمامی ویژگی های رشد رویشی معنی دار شد لیکن اثر دمای تهیه زغال تنها بر ویژگی های وزن تر و خشک برگ و وزن تر ساقه معنی دار بود. دمای تولید زغال زیستی بر انواع کلروفیل (a، b و کل) و شاخص کلروفیل (SPAD) برگ میانی ذرت اثر معنی داری داشت. به گونه ای که مقادیر کلروفیل a، کلروفیل b و کلروفیل کل در تیمارهای زغال های زیستی تولید شده در دمای 700 درجه سلسیوس نسبت به زغال های زیستی تولید شده در دمای 350 درجه سلسیوس 6 درصد افزایش یافتند.

    کلیدواژگان: بقایای کشاورزی، ویژگی های رشد رویشی، زغال زیستی، شاخص کلروفیل، دما
  • محمدرضا بختیاری*، قاسم اسدیان صفحات 33-46

    عملیات بوجاری از جمله فرآیندهای مهم برای افزایش درجه خلوص دانه هاست. تمیز کردن، اساسی ترین کار در یک ماشین بوجاری می باشد، که در آن ناخالصی ها از دانه های سالم جدا می شوند. در این پژوهش سه نوع سیستم بوجاری مختلف مورد بررسی قرار گرفت تا عملکرد آن ها بر روی بازده تمیزسازی بذر گندم آبی مورد مطالعه قرار گیرد. سیستم های بوجاری مورد نظر عبارت بودند از: 1- ماشین بوجاری به همراه ماشین پیش بوجاری آر ماشین (R-Machine) مدل ARS5000 ساخت ایران، 2- ماشین بوجاری به همراه ماشین پیش بوجاری رام صنعت (Ram-Sanat) مدل RAM200 ساخت ایران 3-ماشین بوجاری به همراه ماشین پیش بوجاری گلدسات (Gold-Saat) مدل GS100S ساخت آلمان. در این پژوهش اثر سیستم های مختلف بوجاری بر فاکتورهای مهمی از قبیل: توانایی هر سیستم در میزان تمیزسازی بذر گندم و درصد تلفات دانه سالم در تمامی خروجی های مختلف هر سیستم (شامل ماشین های پیش بوجاری و بوجاری)، بررسی شد. به منظور تحلیل نتایج از طرح پایه کاملا تصادفی استفاده شده و میانگین ها با آزمون دانکن مقایسه شدند. نتایج تحلیل آماری داده ها نشان داد که بین میانگین های درصد خلوص نهایی (بازده) هر یک از سیستم های بوجاری اختلاف معنی داری مشاهده نگردید و درصد خلوص نهایی همه آن ها بیش تر از 98 درصد بود. نتایج نشان داد که میزان تلفات از خروجی استوانه مشبک ماشین پیش بوجاری صفر بود ولی میزان تلفات گندم سالم برای سایر خروجی های هر سیستم (ماشین پیش بوجاری و ماشین بوجاری) در سطح احتمال 1 درصد معنی دار بود. به علاوه کمترین میزان تلفات گندم به سیستم بوجاری رام صنعت تعلق داشت.

    کلیدواژگان: بذر گندم، تلفات، ماشین بوجاری، درصد خلوص
  • اعظم رضوی نسب*، امیر فتوت، علی رضا آستارایی، احمد تاج آبادی پور صفحات 47-59

    استفاده از مواد بهساز آلی و شیمیایی ارزان قیمت در باغ های پسته می‎تواند منجر به افزایش تولید این محصول استراتژیک گردد. به همین منظور آزمایشی به صورت کرت‎های دوبار خرد شده در قالب طرح بلوک‎های کامل تصادفی در سه تکرار، جهت بررسی تاثیر مواد آلی (کمپوست زباله شهری و کود گاوی) به میزان 15 تن در هکتار، مواد شیمیایی (گچ و گوگرد) به میزان 10 تن در هکتار در مزرعه ایزدیاران در 30 کیلومتری جنوب سیرجان اجرا شد. مواد بهساز در اسفند 1390 همزمان با کاشت نهال پسته یک ساله (رقم بادامی سیرجان)، در گودال کاشت (400 گرم مواد آلی و 270 گرم مواد شیمیایی) ریخته و در مرداد سال بعد نمونه برداری از برگ‎ها و در اسفند سال بعد نمونه برداری از سه عمق خاک (20-0، 40-20 و 60-40 سانتیمتری) جهت اندازه گیری غلظت عناصر صورت گرفت. نتایج (با احتمال 5% معنی‎دار) نشان داد بیشترین پتاسیم قابل جذب خاک از همراهی کمپوست و گوگرد در عمق 60-40 سانتیمتری بدست آمده درحالی‎که بر غلظت پتاسیم برگ معنی‎دار نبود. کاربرد گوگرد باعث افزایش کلسیم محلول خاک و کود گاوی باعث افزایش غلظت کلسیم برگ گردید. بیشترین میزان منیزیم محلول خاک از کاربرد کمپوست به همراه گچ در عمق 40-20 سانتیمتری بدست آمد و بیشترین نیتروژن برگ از تلفیق کود گاوی و گوگرد حاصل شد. بیشترین غلظت فسفر قابل جذب از کاربرد کودگاوی در عمق 40-20 سانتیمتری بدست آمد که باعث افزایش معنی‎دار غلظت فسفر برگ نیز گردید. درواقع می‎توان از تلفیق مواد آلی و شیمیایی دردسترس کشاورز، باعث بهبود تغذیه گیاه گردید.

    کلیدواژگان: پسته، کمپوست زباله شهری، کود گاوی، گچ، گوگرد
  • وفا بوعذار، نفیسه رنگ زن*، حبیب الله نادیان قمشه صفحات 61-80

    استفاده از فاضلاب‏ و پساب‏ شهری و صنعتی (به عنوان آب‏های با کیفیت کمتر برای کشاورزی) می تواند منجر به تجمع تدریجی برخی از عناصر سنگین در خاک شود که با ورود به زنجیره غذایی می‏توانند سلامت موجودات زنده را تهدید کنند. با توجه به هزینه های گزاف پاکسازی های فیزیکی، استفاده از روش‏هایی که باعث کاهش اثرات آلودگی‏های موجود در محیط می‏شوند، منطقی‏تر به نظر می‏رسد. به همین منظور آزمایشی گلدانی در قالب فاکتوریل در طرح پایه کاملا تصادفی با 3 تیمار دوده ی‏کربن و ضایعات مو (هر کدام در دو سطح صفر و سه درصد وزنی به عنوان جاذب) و آب آبیاری (در دو سطح آلوده و غیرآلوده) با استفاده از گیاه کاهو و اسفناج در 3 تکرار (در مجموع 36 نمونه) اجرا گردید. نتایج نشان داد استفاده از آب آلوده باعث کاهش معنی‏دار شاخص‏های رشدی هر دو گیاه گردید که این میزان کاهش با کاربرد جاذب‏ها محدود می شود. استفاده از دوده ی کربن و ضایعات مو باعث کاهش غلظت سرب گیاه اسفناج به ترتیب به میزان 58 و 25 درصد گردید که در مورد گیاه کاهو کاهش 54 درصدی در میزان سرب با بکارگیری دوده ی کربن مشاهده گردید. مقایسه تاثیر جاذب‏ها نشان داد در مورد گیاه اسفناج، دوده ی کربن غلظت کادمیوم گیاه را 76 درصد کاهش داد که این مقدار در مورد گیاه کاهو 69 درصد می باشد. اثر ضایعات مو  بر مقدار کادمیوم در هردو گیاه غیرمعنی دار بود. بنابراین دوده ی‏کربن بیشترین مقدار جذب سطحی فلزات را داشته و لذا موثرتر از ضایعات مو در کاهش اثرات منفی آنها عمل کرده است.

    کلیدواژگان: فلزات سنگین، دوده ی‏کربن، ضایعات مو، اسفناج، کاهو
  • مرضیه مزرعه، رویا زلقی*، نعیمه عنایتی ضمیر صفحات 81-93

    به منظور بررسی تاثیر باکتری های محرک رشد بر برخی ویژگی های شیمیایی و بیولوژیکی خاک تحت کشت ذرت و گندم، آزمایشی در قالب طرح کاملا تصادفی شامل دو گیاه ذرت و گندم و سه سطح مایه زنی شامل بدون باکتری، Pseudomonas sp. strain Rhizo_9 و Enterobacter cloacae strain Rhizo_33 در 3 تکرار در گلدان های تقسیم شده (ریزوباکس) و در شرایط گلخانه اجرا گردید. در پایان دوره کشت، گیاه برداشت و خاک های ریزوسفری1 (چسبیده به ریشه)، ریزوسفری2 (چسبیده به مش) وغیرریزوسفری (دور از مش) جدا و برخی ویژگی های خاک اندازه گیری شدند. نتایج نشان داد میزان هر یک از اجزاء کربن و همچنین تنفس پایه و برانگیخته در تیمارهای دارای باکتری بیشتر از شاهد و در خاک تحت کشت ذرت بیشتر ازخاک تحت کشت گندم بود. بیشترین میزان تنفس پایه میکروبی (31/0 میلی گرم CO2 بر گرم بر روز)، تنفس برانگیخته (65/1 میلی گرم CO2 بر گرم بر روز)، کربن قابل اکسید با پرمنگنات (1/213 میلی گرم بر کیلوگرم) و کربن زیتوده میکروبی (53/17 میلی گرم بر صد گرم) درخاک ریزوسفری1 در کشت ذرت مایه زنی شده با باکتری سودوموناس و بیشترین مقدار کربن آلی (82/0 درصد)، کربن محلول در آب سرد (1727 میلی گرم بر کیلوگرم) و کربن محلول در آب داغ (955 میلی گرم بر کیلوگرم) درخاک ریزوسفری1 در کشت ذرت مایه زنی شده با باکتری انتروباکتر به دست آمد که نشان دهنده تاثیر متفاوت دو باکتری بر افزایش اجزاء گوناگون کربن خاک می باشد. همچنین کاربرد هر دو باکتری موجب افزایش وزن خشک ریشه و اندام هوایی هر دو گیاه شد که در این میان تاثیر انتروباکتر بیشتر از سودوموناس بود.

    کلیدواژگان: اجزاء کربن خاک. انتروباکتر کلوآسه، ریزوسفر گیاه، سودوموناس، ویژگی های بیولوژیک خاک
  • مصطفی پارسایی، مصطفی کیانی ده کیانی*، ذبیع الله مهدوی فر صفحات 95-108

    یکی از راکتورهای که امروزه برای تولید بیوگاز استفاده می شود، راکتور  SGBR می باشد. در این پژوهش پارامترهای اساسی در طراحی یک راکتور SGBR  آزمایشگاهی به حجم کل 6/5 لیتر با 25 درصد محیط گرانولی برای هضم ویناس نیشکر محاسبه گردید. این راکتور برای تولید بیوگاز می بایست حداقل دارای تحمل فشار 48/4 بار باشد.  همچنین به منظور تامین دمای راکتور با استفاده از حمام آب، حداقل به المنت 261 وات نیاز می باشد. همچنین عملکرد این راکتور در در سه زمان ماند هیدرولیکی 2، 3 و4 روز و دمای ترموفیل 55 درجه سلسیوس مورد بررسی قرار گرفت.  نتایج نشان داد که میزان روزانه گاز متان تولید شده در سه زمان ماند هیدرولیکی 2، 3 و4 روز به ترتیب  پس از گذشت 13،  12 و 10 روز به مقدار ثابت 4600، 4800 و 4900 میلی لیتر در روز رسید. همچنین مقدار  متوسط گاز متان تولیدی به ازای مواد جامد فرار ویناس در سه HRT 2، 3 و 4 روز به ترتیب 379 ، 380 و 433  CH4(L)/VS(kg)  بدست آمد. بیشترین میزان گاز متان تولید شده m3/kgCOD 582/0 بوده که در HRT 2 روز بدست آمد و بیشترین میزان درصد کاهش COD در این پژوهش 39 درصد بوده که در HRT 4 روز بدست آمد. به طور کلی نتایج بدست آمده، نشان می دهد که این راکتور برای تولید بیوگاز از ویناس نسبت به دیگر راکتورها عملکرد بهتری دارد، اما از نظر کاهش آلایندگی مناسب نمی باشد.

    کلیدواژگان: راکتور، SGBR، طراحی، بیوگاز، ویناس
  • حامد غفارزاده زارع، علی ملکی*، محسن ایرانی رهقی، مجید لشگری صفحات 109-125

    در این تحقیق پارامترهایمودالکوبنده کمبایندرشرایطکاری واقعی تحت بار محیطی با استفاده از آنالیز مودال عملیاتی به شیوه غیر پارامتریک و به روش تجزیه فرکانس تخمین زده شد. کمباینبهوسیلهموتوروارتعاشاتناشیاز قسمت هایکاریمختلفتحریکشد و سیگنال های شتاب با استفاده از سنسور شتاب سنج در شش سرعت مختلف کوبنده جمع آوری شد. با بررسی پارامترهای سیگنال شامل میانگین، فاکتور ضربه، جذر میانگین مربعات، انرژی و انتروپی در دورهای مختلف کوبنده مشخص شد این پارامترها در دورrpm 1000 نسبت به دیگر دورها بطور معناداری مقادیر بالاتری  دارند. که وجود اغتشاش در این دور را تایید می کرد. بنابراین  به بررسی پارامترهایمودالسازهبه روش تجزیه فرکانس در دورrpm 1000 پرداخته شد و مدل اجزای محدود از کوبنده طراحی و با اطلاعات به دست آمده از آنالیز مودال تطبیق داده شد. بابررسیمحدودهفرکانس هایطبیعیوفرکانس هایتحریکواحدکوبنده یکفرکانسرزونانسبرایموداولسازه موردنظریافتشد کهعمده ترینعاملایجادارتعاشدرواحدکوبنده تشخیص داده شد. فراینداصلاحسازهبا اضافه کردن دو میله با قطر یک سانتی متر بین دو فلنچ میانی کوبنده انجام گرفت و مشاهده شد موقعیتفرکانسطبیعی مود اول به 08/32 هرتز تغییر یافت. با فاصله گرفتن از فرکانس طبیعی از فرکانس تحریک،شرایطایجاد پدیده رزونانسودر نتیجهارتعاشات کوبندهکاهش یافت.

    کلیدواژگان: اصلاح سازه، آنالیز مودال عملیاتی، کوبنده کمباین
  • یاسر عظیم زاده، نصرت اله نجفی*، عادل ریحانی تبار، شاهین اوستان، علی رضا ختائی صفحات 127-146

    بیوچار و هیدروچار مواد جامد کربنی هستند که از کربونیزه شدن زیست توده های آلی تولید می شوند. بیوچار با گرماکافت زیست توده های خشک اما هیدروچار با کربونیزه شدن گرمآبی زیست توده های خشک و یا مرطوب تولید می شود. در این پژوهش، بعد از تولید بیوچار و هیدروچار از چوب سیب، با ترسیب ذرات هیدروکسید دوگانه لایه ای (LDH) بر روی سطوح بیوچار و هیدروچار، به ترتیب ترکیب های LDH-بیوچار و LDH-هیدروچار ساخته شد و هر گرم از این ترکیب ها به ترتیب با 51 و 47 (میلی گرم فسفر بارگذاری شد (LDH-P-بیوچار و LDH-P-هیدروچار). سپس با استفاده از یک آزمایش گلخانه ای به صورت فاکتوریل در قالب طرح پایه کاملا تصادفی با 3 تکرار، اثر بیوچار، هیدروچار، LDH، LDH-بیوچار، LDH-هیدروچار، LDH-P-بیوچار و LDH-P-هیدروچار در حضور و عدم حضور کود مونوکلسیم فسفات بر وزن شاخساره و ریشه خشک، غلظت نیتروژن، فسفر و پتاسیم شاخساره و غلظت فسفر و پتاسیم ریشه ذرت بررسی شد. نتایج نشان داد که بیوچار نسبت به هیدروچار دارای درصد عملکرد و خاکستر، pH و EC بیشتری بود و غلظت عناصر مورد بررسی به جز نیتروژن در بیوچار بیشتر از هیدروچار بود. با مصرف کود فسفر در خاک، وزن شاخساره و ریشه خشک در تمام سطوح اصلاحگر به جز LDH-P-بیوچار و LDH-P-هیدروچار نسبت به تیمار بدون اصلاحگر افزایش یافت. بیشترین وزن شاخساره و ریشه خشک گیاه در تیمارهای LDH-P-بیوچار و LDH-P-هیدروچار و کم ترین وزن شاخساره و ریشه خشک در حضور LDH به دست آمد. مصرف کود فسفر در حضور LDH-بیوچار و LDH-هیدروچار باعث افزایش معنادار غلظت فسفر شاخساره و ریشه ذرت شد اما بر غلظت نیتروژن و پتاسیم شاخساره اثر معنادار نداشت و غلظت پتاسیم ریشه را در حضور بیوچار و LDH-بیوچار و در شاهد کاهش داد. بیشترین غلظت فسفر شاخساره و ریشه و بیشترین غلظت نیتروژن شاخساره در دو تیمار LDH-P-بیوچار و LDH-P-هیدروچار مشاهده شد. کود فسفر با بیوچار، هیدروچار، LDH-بیوچار و LDH-هیدروچار در افزایش وزن شاخساره و ریشه خشک و غلظت فسفر شاخساره و ریشه گیاه برهم کنش هم افزایی ولی با LDH، LDH-P-بیوچار و LDH-P-هیدروچار برهم کنش ناهمسازی داشت. بنابراین، مصرف بیوچار، هیدروچار، LDH-بیوچار و LDH-هیدروچار به همراه کود فسفر و ترکیب های LDH-P-بیوچار و LDH-P-هیدروچار بدون مصرف کود فسفر برای کشت ذرت در شرایط مشابه می تواند پیشنهاد شود.

    کلیدواژگان: بیوچار، ذرت فسفر، کربنیزه شدن، هیدروچار، هیدروکسید دوگانه لایه ای
  • سمانه تاجیک، شمس اله ایوبی*، محمدمهدی درویشی، حسین خادمی صفحات 147-160

    حلزون های خاکزی، بخش مهمی از اکوسیستم جنگل را شامل می شوند و نقش مهمی در تجزیه لاش برگ و غلظت کلسیم خاک دارند. این مطالعه با هدف بررسی ویژگی های خاک و پارامترهای توپوگرافی موثر بر فراوانی حلزون های خاکزی و هم چنین پیش بینی پراکنش فراوانی آن ها دربخشی از اراضی جنگلی استان گلستان آن جام گردید. تعداد 153 نمونه خاک از عمق 0-10 سانتی متر جمع آوری شد؛  سپس حلزون های خاکزی جمع آوری و تاسطح رده شناسایی و طبقه بندی شدند. ویژگی های خاک از طریق آنالیزهای آزمایشگاهی و پارامترهای توپوگرافی، با استفاده از نقشه رقومی ارتفاع منطقه و تصاویر ماهواره ای به دست آمدند. بر طبق نتایج حاصل مدل غیر خطی جنگل تصادفی دارای ضریب تبیین 49/0 و خطا 82/1 است و دقت بالاتری نسبت به مدل رگرسیون خطی با ضریب تبیین 28/0 و خطا 13/2 در پیش بینی فراوانی حلزون ها دارد. نتایج به دست آمده از آنالیز مولفه های اصلی و آنالیز حساسیت نشان دادند که کربنات کلسیم معادل، pH، EC و کربن آلی، از جمله مهم ترین ویژگی های خاکی موثر بر فراوانی حلزون ها هستند. پارامترهای توپوگرافی دارای روابط خطی با فراوانی حلزون های خاکزی نداشته اند اما در مدل غیر خطی به خوبی نقش آن ها نشان داده شده است. جهت شیب، ارتفاع و دمای سطح زمین از جمله مهم ترین پارامترهای تاثیرگذار بر فراوانی حلزون ها بوده اند که احتمالا تاثیر آن ها به دلیل تاثیر بر ویژگی های خاک مانند کربنات کلسیم و رطوبت خاک بوده است.

    کلیدواژگان: ویژگی های خاک، توپوگرافی، مدل سازی، رگرسیون، جنگل تصادفی
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  • Sahar Akhavan, Soheila Ebrahimi *, Maryam Navabian, Mahmoud Shabanpour, Alireza Movahedi, Ali Mojtahedi Pages 1-12
    Introduction

    Soil macropores are the prominent factor in the transfer of wastewater, fertilizers, and microorganisms, including fecal bacteria to deeper soils and even underground waters. On the other hand, a vast majority of land in Iran is located in arid and semi-arid regions. Therefore, the use of salty and unconventional waters has recently gained considerable importance. The aim of this study is to investigate the preferential transportation and storage of Escherichia coli (as an important bacterium in commonly used fertilizers) under the condition of saline water application.

    Materials and methods

    The laboratory studies were conducted in a preferential flow system with artificial macropores with different diameters (1 and 2 cm) and varying salinity treatments (1, 2 and 4 dsm-1) under a saturated flow condition. The leaching test was performed at 20°C within several phases. Microbial transfer tests were carried out in two phases with boundary conditions and flow velocities similar to the zero-phase condition. In order to evaluate the bacteria in the soil profile, after the end of the bacterial transfer test, the soil column was divided and cut into 3 layers. Two samples were collected from 3 depths and at macropore and matrix zones. The experiment was conducted in a factorial format and completely randomized design with three replications. The results showed that the mutual effect of salinity and macropore diameter was significant (at 5%) on mean output concentration (Cav), soil filtration coefficient (fλ), relative absorption index (SR), and maximal predicted depth of bacteria transfer (Zmax).

    Results

    The results indicated that the bacteria were affected by the treatments during the transfer, so that with increasing the salinity and reducing the diameter of macropores, the average bacterial concentration output decreased. The presence of macropores and the integrity of pores in a column with a diameter of 2 cm accelerated the bacterial movement and increased the pollutant outflow index due to high porosity; therefore, more bacteria passed (compared to the control column without macropores). The salinity treatment, however, served as an inhibitor and hindered further transmission of bacteria. Moreover, The macropore-free column with a salinity of 4 dsm-1 exhibited a higher refining coefficient (0.85 cfuml-1) compared to other treatments. A salinity treatment involving a 1 dsm-1 salinity and a pore diameter of 2 cm showed the least filtration coefficient (0.82 cfuml-1), so by doubling the ionic strength, 30% reduction can be seen in the bacterial filtration coefficient. Increasing the salinity up to 2 dsm-1 and decreasing the macropores diameter increased the relative absorption index. The macropore-free treatment with a 2 dsm-1 salinity showed the highest relative sorption index (0.92). Although the bacterial growth and mortality are unknown during the bacterial transfer process, according to the results, it is expected that the bacterial mortality rate increases by the salinity enhancement from 2 to 4 dsm-1 and the relative adsorption index reduction which may result in lower surface sorption. The significant treatment for the maximum predicted depth of bacterial transfer was the mutual effect of salinity and diameter at a probability level of 5%, which confirmed the significant impact of salinity on the bacterial filtration and transfer. The maximum depth of predicted bacterial transfer was obtained in the macropore-free treatment with the salinity of 1 dsm-1 (16.81 cm). The role of the underlying layers in the bacterial refinery seems to be more profound compared to the surface layer.

    Conclusion

    Overall, the results showed that the main source of transmission of bacteria is the preferential flow due to the macropore continuity. However, the salinity reduced the amount of bacterial refining by increasing the ionic strength of the soil solution. The salinity had a significant effect on the average output bacterial concentration, bacterial refining coefficient, relative sorption index, and maximum predicted bacterial transmission depth. The results of this study revealed that increased ionic strength of soil solution can enhance the bacterial refining and the further elimination of bacteria which can be effective in controlling the pollution of underground water by saline irrigation management. Regarding the quantitatively and qualitatively critical water status in the country, conditions can be provided for the use of unconventional water sources, without threatening the environment and contaminating the underground water.

    Keywords: Bacterial filtration, Preferential flow, Bacteria absorption index, Matrix, Macrospore, Salinity
  • Narges Sousaraes, Mojtaba Baranimotlagh *, Farhad Khormali, Esmaeil Dordipour Pages 13-31
    Introduction

    Biochar is a charcoal, pyrolyzed from a wide range of carbon-rich biomass materials, such as crop and wood residues, animal manures and a range of industrial wastes and once added into soil, it can store the soil carbon for a long period, improve the soil structure and increase the crop yield. However, the physical and chemical characteristics of biochars are influenced by the properties of the feedstock and pyrolysis conditions, such as highest temperature treatment and furnace residence time. Considering the large variation in biochar properties, it is not surprising that crop yields vary with different biochars. We investigated the effects of biochars on corn growth in the greenhouse. The specific objectives were (a) to assess whether feedstock properties or pyrolysis temperature are important in preparing of biochar and (b) to quantify the effects of varying biochar characteristics on corn growth and chlorophyll index in a calcareous soil under greenhouse condition.

    Materials and Methods

    Biochar was produced from crop residues including rice, cotton and canola. Feedstock was oven-dried before pyrolysis. The pyrolysis process was conducted for 1 h at 10°C min‒1 heating rate to produce biochars at different temperatures of 350 and 700 oC under oxygen-limited conditions. All biochars were ground and passed through a 2-mm sieve before experimentation. Ash content and char yield was calculated and biochar pH and electrical conductivity (EC) were measured using 1:20 solid: solution ratio. The soil used in this experiment was taken from the Research Farm of Gorgan University of Agricultural Sciences and Natural Resources. The soil was air-dried and ground to pass through a 2-mm sieve then analyzed for various soil physico-chemical properties using standard methods. A greenhouse experiment was set up using pots with 5 kg prepared soil. Various treatments comprising of 3 biochars type produced at different pyrolysis temperatures (350 and 700°C) from three crop residues (rice, cotton and canola) at three application rates (0, 2 and 5% w/w). A completely randomized design was used in factorial arrangement and treatments were replicated four times. After the soil had been prepared and biochar added, six seeds of maize were planted approximately 20 mm deep in the center of the pots and thinning to seedlings of four plants pot‒1 was done at plant establishment. Distilled water was used to maintain moisture contents of the soil in all the pots during the experimental period. Plant stem and leaves were harvested 96 days after planting. Washed with distilled water then dried with tissue paper. The leaf and stem samples were air-dried and then oven dried at 65˚C to a constant weight in a forced air driven oven. The studied traits included leaf and stem fresh and dry weight, plant height, number of leaves, time to first flowering, chlorophyll index (SPAD), concentration of chlorophyll a, chlorophyll b and total chlorophyll. The analysis of variance (ANOVA) with the factors biochar type, application rate and pyrolysis temperature were performed using a completely randomized design. Significantly different treatment means were separated using least significant difference (LSD) test at P

    Results and Discussion

    The results showed that pyrolysis temperature significantly influenced the measured chemical properties of biochars. EC values were tended to increase with pyrolysis temperature. The pH of the biochars was also influenced by temperature. Biochars pH ranged from 6.8 to 9.6. The pH of the biochars was increased with increasing temperature and highest pH (9.6) was observed at 700°C of rice residues. These increases in pH values are mainly due to separating of alkali salts from organic materials by increased pyrolysis temperature. The results showed that the yield of biochars was reduced by increasing pyrolysis temperature and ranged from 19.4% to 40.1%. This decline in yield content is mainly due to the destruction of some compounds such as cellulose and hemicellulose as well as combustion of organic materials with increased pyrolysis temperature. By contrast to biochar yield, the biochar ash content increased with increasing pyrolysis temperature. The lowest values of leaf and stem fresh and dry weight was observed at 700°C of canola residues. These results suggest that biochar produced at high pyrolysis temperature (especially at 700°C), when applied to the soil, may increase soil salinity and subsequently provide undesirable impacts on the plant growth. It has been reported that the negative impacts of high salinity on the plant growth could be due to the following reasons:

    (1) the low osmotic potential of the soil solution, resulting in water stress,

    (2) specific ion effects, resulting in salt stress, and

    (3) nutrient imbalances. Addition of each three types of biochars caused a significant increase in chlorophyll concentration compared to control.

    Conclusion

    The type of feedstock material is an important factor that determines the final application of the biochar and its effect on plant growth papameters. Therefore, there is further need for research focusing on the effects of biochar addition on soil properties and plant growth in order to assess biochar as a valuable resource for agriculture.

    Keywords: Agricultural residues, Biochar, Chlorophyll index, Temperature, Vegetative gowth parameters
  • Mohammad Reza Bakhtiari *, Ghasem Asadian Pages 33-46
    Introduction

    The cleaning operation is an important process to increase the seeds’ purity degree. Cleaning is the most fundamental task in a cleaning machine, which separates the impurities of the healthy seeds. In a research that was conducted by Chenari et al. (2013), The efficiency of three types of wheat cleaning machines, R-Machine, Cimbria, and Gold-Saat, was investigated. The results of the statistical analysis showed the Cimbia machine had the greatest cleaning efficiency (86.72%). The R-Machine and Gold-Saat had 80.64% and 81.59% total efficiency, respectively. In this study, the effects of three different cleaning machines were evaluated on the seed losses percentage and seed cleaning percentage of all outputs in various pre-cleaning and cleaning machines for cleaning wheat seeds.

    Materials and Methods

    In this study, three types of various cleaning systems were investigated to study their performances on wheat cleaning rate in Hamedan Province. Generally, a cleaning system is constructed of 5 parts: (1) pre-cleaning machine, (2) cleaning machine, (3) Trieurs, (4) weighting system, (5). packaging system. In this study, the term  cleaning system refers to only the first and the second part of the cleaning system. The cleaning systems in the study were (Table 1): (1) R-Machine with pre-cleaning machine model ARS2000, made in Iran, (2) Ram-Sanat with pre-cleaning machine model RAM200, made in Iran, and (3) Gold-Saat with pre-cleaning machine model GS100S, made in Germany. Table 1 shows the characteristics of three different cleaning systems, containing cleaning and pre-cleaning machines. Fig. 1 shows a schematic of the inputs and outputs of the wheat cleaning system (containing pre-cleaning and cleaning machines with Trieurs). Some factors were considered and determined as the following: (1) theoretical and practical capacity in ton/ha: based on the factory’s manual, the theoretical capacity for pre-cleaning machine and cleaning machine were 20 and 5 tons/ha, respectively; whereas, the practical capacity was calculated 2.2 tons/ha for total system (pre-cleaning machine and cleaning machine); (2) purity percentage of wheat input: this factor was determined for the pre-cleaning machine as follows: purity percentage of healthy seeds input = (weight of healthy seeds / total weight) × 100; (3) loss percentage of all outputs in the pre-cleaning machine, loss percentage of all outputs in the cleaning machine, and the total loss percentage of the system, as below: Loss percentage of each of output on the cleaning system = (weight of lost seeds / total weight) × 100. A completely randomized design was used in the research and Duncan’s test was used to compare the means results.

    Results and Discussion

    Table 2 shows the means of different parts of cleaning systems (containing pre-cleaning and cleaning machines) by Duncan’s method. Thus:

    Pre-Cleaning Machine

    Wheat input impurity or purity percentage: Table 2 indicates non-significant differences between wheat input impurity and purity percentage as affected by various wheat input to the cleaning system. Loss percentage in the second suction of the pre-cleaning machine: Table 2 indicates significant differences between loss percentage in the second suction of the pre-cleaning machine. The maximum loss percentage belonged to Ram-Sanat, and the Gold-Saat had the minimum amount.

    Cleaning Machine

    Loss percentage in suction: the result shows significant differences between loss percentage in primary and final suction of the cleaning system. Loss percentage in sieves of the cleaning machine: Table 2 indicates significant differences between loss percentage in the top of the upper sieve and below th downer sieve of the cleaning machine. Loss percentage in barely cleaning and semi-wheat cleaning parts: based on Table 2, a significant difference between them is observed. The maximum losses belonged to Ram-Sanat, and the R-Machine had the minimum amount.

    Cleaning System (Pre-Cleaning and Cleaning Machine Combination)

    Purity percentage of wheat output (last purity): the results of the analysis of the variance show that all cleaning machines have the seed final purity percentage greater than 98%. Total loss percentage of the system: the results show that the total loss percentage of Gold-Saat, R-Machine and Ram-Sanat are 6.04%, 2.97% and 4.4%, respectively. Also, the results show that seed loss is zero for meshed cylinder, but the wheat loss of pre-cleaning and cleaning machines for all outlets is significant (p < 1%). These results are in agreement with Safarzadeh, (1993) and Jilanchi et al., (1997).

    Conclusion

    The results show that all three cleaning machines have the final purity seed percentage greater than 98%, and also the minimum wheat loss (3.0%) belonged to Ram-Sanat cleaning machine. The R-Machine and Gold-Saat had 4.4% and 6.0% total loss.

    Keywords: Wheat seed, Losses, Cleaning machine, Purity percentage
  • Azam Razavi Nasab *, Amir Fotovat, Alireza Astaraie, Ahmad Tajabadipour Pages 47-59
    Introduction

    Pistachio is one of the most economical cash crops in Iran that is located in arid and semi-arid regions with low soil organic matter and very harmful ions. The enhancement of the organic matter in sufficient quantity and quality plays an important role in agricultural production and soil sustainable management. The application of organic matter promotes physical, chemical, and microbial soil conditions, such as soil aggregate stability, water holding capacity, productivity, and fertility which are essential, particularly in the arid and semi-arid regions of Iran. Municipal solid waste compost (MSWC) and cow manure are two cheap, available, and effective organic materials that can be used in pistachio orchards to improve soil condition and better root growth and more effective nutrient uptake. Gypsum is a chemical material that can replace Ca with Na, especially in saline and sodic soil and cause Na leaching from the soil profile. Sulfur oxidation and gypsum produce acid in the soil and lead to the reduction in pH and the amending of the soil condition. The present study investigated the effects of two organic matters (MSWC and cow manure), two chemical matters (gypsum and sulfur) on some nutrient concentrations in different soil depths (0-20, 20-40, and 40-60 cm depths) and the leaf of pistachio seedlings at the field condition. 

    Materials and Methods

    A field experiment in a randomized complete block design (split-plot) with three replications was conducted for two years in Izadyaran Company (30 km south of Sirjan, Kerman Province, Iran with hot and dry climates). Treatments were two organic wastes (MSWC and cow manure, 15 Mg ha-1 as the major factor, two chemical amendments (gypsum and sulfur, 10 Mg ha-1) as subplot factor, and soil depths (0-20, 20-40, and 40-60 cm) as the sub-subplot. The organic and chemical matter were poured into the pit of planting and mixed well with soil and a one-year-pistachio seedling was planted (February 2012). In the middle of the summer (August 2013) and at the end of winter (February 2014), plant leaves and soil sampling were done respectively and macro elements’ (Na, K, Ca, Mg, N, and P) concentrations were measured and then statically analyzed with SAS software.

    Results and Discussion

    MSWC and sulfurs cause the increase of available K in 40-60 cm depth, because of more mobility of K in comparison to other ions. MSW contains K and sulfur through the reduction in pH that leads to MSW decomposing and increases the available K. Sulfur application rises Ca of soil solution more than gypsum because of common ion effect. MSWC and gypsum also enhanced Mg of the soil solution in 20-40 cm depth. Not only MSWC contained Mg but also SO42- solved some parts of solid MgCO3 and increased Mg in soil solution. On the other hand, mineralization of cow manure increased the available P in 20-40 cm depth. None of the treatments were significant on the concentration of soil Na and N. Probably Na was leaching in primary irrigation and mineralized N was quickly absorbed by the plant. Results of this experiment showed that treatments were not significant on the concentration of Na, K, and Mg of pistachio leaves. The application of cow manure increased Ca and P, and cow manure and sulfur increased the N concentration of leaves. The enhanced concentration of elements may be attributed to the increased nutrient levels in cow manure. Sulfur because of sulfuric acid production in soil solution, declined soil pH and led to more nutrient uptake. This phenomenon continuously provides available nutrients in usable form to the plants. These results may be illustrated by the postulated slow release and contiguous storage of nutrients from organic wastes, such as MSWC and cow manure that increased soil nutrient content after a year. Gypsum, with replacing Na with Ca, decreased harmful ions, such as Na and both gypsum and sulfur and because of sulfuric acid production in soil solution, declined soil pH and then led to soil reclamation and more nutrient uptake. The interaction effect of organic and chemical matters’ treatments ,in the same way, can increase some essential nutrients in the soil and plant significantly because of the synergic effect of the organic and chemical soil reclamation. 

    Conclusion

    Results of this study illustrated that it is possible to improve the fertility of saline-sodic soils and plant nutrition with cheap and available organic and chemical materials, such as cow manure and MSWC, gypsum, and sulfur. However, due to the difference in mobility of ions, their concentrations vary in different depths, but with the proper planning, the essential elements can be reached to plants at the right time, especially for a strategic plant like pistachio.

    Keywords: Cow manure, Gypsum, MSWC, Pistachio, Sulfur
  • Vafa Bozar, Nafiseh Rang Zan *, Habibollah Nadian Qomsheh Pages 61-80
    Introduction

    Soil quality is very important because of the direct impact on agricultural production and the nutrition of living creatures. The use of urban and industrial wastewaters (as lower quality water for irrigation of plants to reduce raw water consumption) can lead to a gradual accumulation of some heavy metals in the soil, which can enter the food chain and menace the health of creatures. Due to the high costs of the physical cleaning up methods, it is sometimes more logical to use methods that reduce the effects of contaminants in the environment.

    Materials and Methods

    For this purpose, a pot experiment with lettuce and spinach was conducted to investigate the effect of carbon black and hair waste (as adsorbent) on the concentration of cadmium and lead in plants, as well as fresh and dry weight as affected by contaminated water irrigation. Carbon black with defined properties was prepared by the Iranian Carbon Black Company. After collecting the hair waste, all was washed with raw water, diluted acid, and distilled water properly. Then the waste was air dried and ground as much as possible to make it uniform and increase the specific area to cause more reaction between the waste and soil. The waste was applied to the soil at a rate of 3 percent by weight. The carbon black was applied to the soil at the same rate as the hair waste. After preparing the pots, spinach and lettuce were planted in the pots and irrigated with contaminated water and harvested 60 days after sowing. At the end of the pot experiment, some growth parameters, as well as the uptake of some elements, including micronutrients and heavy metals, was measured by standard methods. The data were analyzed by using SAS and graphs were plotted with the help of Excel program. So, this study was carried out in a completely randomized design with three treatments, including carbon black (two levels of zero and three percent by weight), hair waste (at two levels of zero and three percent by weight), and irrigation water (at two levels of contaminated water and Non-contaminated) with 3 replications.

    Results and Discussion

    The results showed that the use of heavy metal contaminated water significantly reduced the growth parameters in both plants, which was significantly limited by the use of adsorbents, which shows the effect of adsorbents in reducing the negative effects of pollutants in the environment. The analysis of data showed that the effect of carbon black, hair waste, and irrigation water on fresh weight of spinach and lettuce was statistically significant (at the level of 1 and 5%). The interaction effect of carbon black and irrigation water on fresh weight of plants showed that the use of carbon black increased the fresh weight of spinach and lettuce from 16.65 to 19.68 and 11.38 to 16.68, respectively. In the case of treatment of 1.5% carbon +1.5% hair waste, the fresh weight of plants decreased significantly as compared to treatments without hair waste, as well as the control treatment. This can be due to the negative effect of hair waste on the physical properties of soil according to the short time of the research work (2 mounts). More or less, the effect of carbon black and irrigation water on iron, zinc, copper, cadmium, and lead content in both experimented plants was statistically significant. In the case of hair waste effect on iron and lead for spinach, iron and copper for lettuce were statistically significant. The irrigation with contaminated water decreased the amount of iron, zinc, and copper in the aboveground part of plants which is indicating the negative effect of heavy metals in irrigation water on root development and nutrient uptake, as well as competing through antagonistic relationships with micronutrients which are necessary for the plant growth. In the treatments containing 3% carbon black, the number of micronutrients in plants increased significantly due to surface absorption of heavy metal on carbon black and the reduction in the negative effect of heavy metals in soil. In the case of cadmium and lead, the reverse trend was observed. In spinach application of 3% carbon black decreased cadmium and lead content at the rate of 76% and 58%. In the case of hair waste, the effect on lead content at the rate of 25% was significant but for cadmium was not significant. In aboveground parts of lettuce, carbon black reduced cadmium and lead content at the rate of 69% and 54%, respectively. Same as spinach, the effect of hair waste on cadmium content was not significant. The results showed that carbon black had the highest amount of metal adsorption capacity and, therefore, can be more effective than hair waste.

    Conclusion

    According to the results, carbon black can be used in the agricultural system which requires more research in the case of its ability.

    Keywords: Heavy metals, Carbon black, Hair waste, Spinach, Lettuce
  • Marzieh Mazraeh, Roya Zalaghi *, Naiemeh Enayatizamir Pages 81-93
    Introduction

    Growth-stimulating bacteria are now proposed as an alternative to chemical fertilizers in order to increase soil fertility in sustainable agriculture. Biofertilizers are also expressed as microbial inoculants that are capable of removing soil nutrients from an inaccessible state through biological processes. Plant Growth Promoting Bacteria (PGPRs) refer to a broad group of susceptible bacteria, which grow alongside the plant as the host and stimulate plant growth. On the other hand, these microorganisms in the soil are able to stimulate and improve biological indicators, such as microbial carbon biomass, microbial respiration, and microbial yield, and may also affect different forms of carbon in the soil. Among the PGPRs, it is possible to refer to Enterobacter and Pseudomonas. Pseudomonas are bacteria present in all agro-soils and have different growth-promoting characteristics. Enterobacteriaceae family is a large group of bacteria that are naturally present in the water, soil, and materials that are corrupted and contaminated. To evaluate the biological changes of soil due to the activity of PGPRs, biochemical parameters (microbial respiration and microbial carbon biomass) are usually monitored in the plant's rhizosphere. The rhizobox is one of the tools used to study the changes in the rhizosphere, by limiting the roots in a certain volume of soil and facilitating the sampling of rhizosphere soil. The aim of this study was to investigate the effect of plant growth-promoting bacteria on some biological and chemical properties of the soil under Rhizobox conditions.

    Materials and Methods

    In order to study some of the chemical and biological properties of the soil cultivated with maize and wheat and inoculated with growth promoting rhizobacteria (PGPR), a completely randomized design, including two maize and wheat plants and three levels of inoculation, including non-inoculated, Pseudomonas sp. strain Rhizo_9 and Enterobacter cloacae strain Rhizo_33 in three replications in Rhizobox pots was done in greenhouse conditions. At the end of the period, the plants were harvested and the dry weight of roots and shoots was measured. Also, 3 soil samples were sampled from each rhizobox, as follows: rhizosphere 1 (soil clinging to the root), rhizosphere 2 (1 cm soil clinging to mesh), and non-rhizosphere (soil far from the mesh). Some soil characteristics, including basal respiration, substrate induced respiration, metabolic quotient, and soil carbon components (soil organic carbon, microbial carbon biomass, cold-water-soluble carbon, hot-water-soluble carbon, and permanganate oxidable carbon) were measured.

    Results and Discussion

    Results showed that the amount of each carbon component, as well as basal and substrate-induced respiration in treatments with bacteria, was higher than non-bacterial treatments and these biological properties in the soil cultivated with maize were higher than those under wheat cultivation. According to the results, the highest amounts of the basal respiration (0.31 mg CO2 g-1 day-1), the substrate-induced respiration (1.65 mg CO2 g-1 day-1), the permanganate oxidable carbon (213.1 mg kg-1), and the microbial carbon biomass (17.53 mg 100g-1) were related to rhizosphere 1 soil of maize inoculated with Pseudomonas. The highest amounts of the organic carbon (0.82%), the cold-water-soluble carbon (1727 mg kg -1), and the hot-water-soluble carbon (955 mg kg-1) were related to rhizosphere 1 soil in maize inoculated with Enterobacter. This could show the differences between two bacteria in affecting on different forms of carbon in the soil.

    Conclusion

    The results of this study showed that maize had a higher effect on carbon forms of soil that could be because of higher root biomass and probably higher root secretions of maize in comparison to wheat. Also, by increasing the distance from plant roots (from rhizosphere1 soil to bulk soil), different forms of carbon decreased that showed the impact of rhizosphere (plant roots and rhizospheric microorganisms) on physicochemical and biological characteristics.Inoculation of PGPR bacteria caused an increase in soil respiration and soil different carbon forms but the two bacteria were different in increasing various forms of soil carbon that seems to be related to different secretions or different effects of bacteria or plant-bacteria associate on soil carbon forms. Although inoculation of Pseudomonas resulted in a higher amount of microbial carbon biomass, inoculation of Enterobacter resulted in higher amounts of cold-water-soluble carbon, hot-water-soluble carbon, and soil organic carbon. Also, the application of two PGPR bacteria (Enterobacter was more effective) increased root and shoot dry weights of maize and wheat compared to non-bacterial treatments.

    Keywords: Enterobacter cloacae, Pseudomonas sp, Soil biological properties, Soil carbon forms, Soil rhizosphere
  • Mostafa Parsaee, Mostafa Kiani Deh Kiani *, Zabiollah Mahdavifar Pages 95-108
    Introduction

    Anaerobic digestion has progressed rapidly since the late 1960s. With the progress of the anaerobic fermentation process in the world, anaerobic reactors have been developed to digest different types of organic wastes in each country. So various types of reactors have been built, and that they have been in different shapes, dimensions, and operating conditions. One of these reactors is the static granular bed reactor (SGBR). SGBR with its granular bed digests a substrate in less hydraulic retention time (HRT). SGBR is a downstream reactor that consists of active anaerobic granules. The biomass contacts the granular surfaces and does not require the use of mixers, gas, solid, and a separator. The reactor startup is very short since there is no need for some operations, such as extra time to grow microorganisms in the granule. One of the most important residues in the alcohol production plant from molasses is vinesse which has become a major problem in this industry. The conversion of vinasse to biogas and using it to supply the energy of the industry is one of the basic ways to solve this problem. Several studies have been conducted in this field by using various reactors, but there is no research about SGBR. In this study, an SGBR producing biogas from vinasse has been designed and constructed. Also, the performance of the reactor was investigated at three HRTs (2, 3, and 4 days) and the thermophile temperature of 55 °C.

    Materials and Methods

    The best diameter to height ratio (reactor volume) in the SGBR is 1:7. Accordingly, the shape of the reactor is a pipe. Based on the volume of the reactor and the maximum pressure inside it, a 4-inch polyethylene tube with a height of 1 meter was selected to carry out the testes. According to the thermophile temperature (55 °C) and the accuracy of the element (0.9 °C), the maximum temperature of the reactor is 329 K. Therefore, the minimum power for obtaining this temperature is 405.316 watts. The water displacement method was used to measure the amount of biogas. An iron sponge was used for removing hydrogen sulfide gas from biogas. Sodium hydroxide solution was used to remove carbon dioxide from biogas.

    Results and Discussion

    The reactors were loaded daily with organic matter (86002, 28667, and 21500 mgCOD/L.d) for different HRTs (2, 3, and 4 days). For three HRTs, the amount of methane production was high during the first day which is due to the thermal shock caused by the microorganisms in the granule. Methane production in HRT of 2 days had fewer variations than HRT of 3 and 4 days, and after 13 days, it reached a nearly constant value of 4600 ml/day. For HRT of 3 days, the daily rate of methane production reached a constant value of 4800 ml/day after 12 days and for HRT of 4 days, it reached 4,900 ml/day after 10 days. For HRTs of 2 and 3 days, the rate of methane production per unit of volatile solids had less variation and remained constant approximately after 7 days. The average methane production per unit of volatile solids at HRT of 4 is days higher than the other HRTs. The average methane production for HRTs of 2, 3, and 4 was 379, 380, and 433 CH4 (L)/VS (kg), respectively. The maximum value of methane production was 582 m3/kgCOD, which was obtained at HRT of 2 days. In this study, 31 liters of methane were produced per one liter of vinasse at HRT of 4 days, which was more than other studies.

    Conclusion

    In this study, the required heat power and pressure inside the SGBR laboratory have been calculated. The minimum required heat is 261 watts. Also, this reactor should be able to bear at least 4.34 bar for biogas production. The average amount of methane production per unit of volatile solids was 379, 380, and 433 CH4 (L)/VS (kg) at HRTs of 2, 3, and 4 days, respectively. The maximum amount of produced methane was 582 m3/kgCOD, which was achieved at HRT of 2 days, and the maximum percentage of COD reduction was 39%, which was achieved at HRT of 4 days. In general, the results indicated that SGBR produced higher biogas from vinasse than other reactors, but it is not suitable for reducing pollutions.

    Keywords: Reactor, SGBR, Design, Biogas, Vinasse
  • Hamed Ghafarzadeh Zare, Ali Maleki *, Mohsen Irani Rahaghi, Majid Lashgari Pages 109-125
    Introduction

    An important process in grain harvesting with the combine harvester is threshing the materials using the thresher unit. An ideal thresher is one that carries out complete threshing with maximum crop input and best grain separation while saves the shape and quality of the grain and minimizes grain loss. The vibrations of this unit cause the threshing action to fail and combine harvester loss to increase; therefore, it is highly important to study the vibration produced in the threshing unit. Since measuring the vibration in all working conditions on the farm is expensive, one of the ways to achieve the mentioned objectives is to use a vibration model by the simulation methods in order to examine the effects of vibration on the machine’s and the operator’s performance. Using vibration modeling and dynamic analysis of the structure through a mathematical model, finite element, and modal analysis, the causes and effects of the vibration in different working conditions can be examined with minimum cost. The present study was aimed to carry out the dynamic analysis of combine harvester using operational modal analysis. Therefore, the nonparametric and frequency decomposition methods were used in order to extract values of natural frequencies and damping coefficients, and the information obtained from the modal analysis was utilized to design and update the finite element model of the thresher. Afterward, the vibration of the thresher was adjusted as much as possible by modifying the structure through the weight modification method.

    Materials and Methods

    To measure the vibration of the thresher in practical conditions, a piezoelectric accelerometer sensor DYTRAN/MODEL3255A2, an analyzer device, and a signal processing software MEscopeVES were employed. In order to carry out the analysis, the combine harvester was started in its normal conditions and all parts were set in operation. Due to the geometry of the structure, four points were chosen on the bearings of the threshing drum. Afterward, de-noising signals used in MATLAB were utilized to calculate the response power spectral matrix, and singular values decomposition method was applied to it. Finally, by drawing each singular value, resonance peaks of the system were determined with respect to different frequencies, and the system’s damping was estimated. In order to carry out the geometric modeling and the simulation of the thresher by finite element method, ABAQUS finite element software was employed. In order to compare the analytical and the experimental results of NFD value, the predicted and measured natural frequencies were calculated. Modifying the structure as one of the applications of the modal analysis is a technique to consider the effect of physical parameters of a structure on its dynamic properties, i.e. natural frequencies and mode shape in order to improve the structure’s dynamic behavior. In the present study, therefore, modification of the threshing unit was aimed to decrease its vibrations by changing the natural frequency. Due to its complexity, the process of modifying the structure can be carried out by changing the mass and hardness. As presented in the study, modification of the structure was conducted by changing the mass on the finite element model.

    Results and Discussion

    The purpose of this study is to determine the vibration characteristics and present a vibration model of the thresher. The vibration responses of the thresher were recorded in working conditions on the bearings of the thresher. Through investigating signal parameters, including root mean square, energy, and entropy in different speeds of the thresher, it was specified that these parameters had significantly higher values in the rotation speed of 1000 rpm compared to other speeds, which proved the disturbance in the rotation speed of 1000 rpm. By examining the range of the natural and excitation frequencies of the threshing unit and also considering the diagram obtained from decomposing the singular values of the power spectral density matrix and Campbell diagram, a resonance frequency was found for the given structure, which is the major cause of vibration in the thresher. Moreover, the speed of 1000 rpm was determined as the critical speed of the thresher. In order to reduce the level of vibrations, the thresher’s excitation frequency should be far enough from the natural frequency; therefore, the process of modifying the structure is carried out by changing the mass applied to the finite element model, and it was observed that the natural frequency of the first mode changed from 16.98 Hz to 12.4 Hz.

    Keywords: Frequency analysis Method, Structural modification, Finite element model
  • Yaser Azimzadeh, Nosratollah Najafi *, Adel Reyhanitabar, Shahin Oustan, Alireza Khataee Pages 127-146
    Introduction

    Phosphorus (P) is an essential element for living organisms. Discharging P from various sources, such as industrial wastewater and agricultural waters, into surface water causes eutrophication and undermines the balance of aquatic ecosystems and imposes many costs due to water quality degradation. In addition, mineral resources of P-fertilizers in the world are unrecoverable and are coming to an end. Therefore, it is very important to develop adsorbents to remove P from contaminated water and then be used as P-fertilizer for surmounting the eutrophication and P-fertilizer exhausting challenges. In the last few years, biochar and hydrochar have been considered as low-cost porous eco-friendly adsorbents with a high surface area and easy to produce and use. Biochar and hydrochar are carbonaceous solids that are produced from the carbonization of biomasses and could be used as adsorbents and soil amendments. However, because of their high negative charge and very low ability to absorb anions, especially phosphate, they cannot be used as phosphate adsorbents. In recent years, several methods have been introduced to change the surface of biochar and hydrochar to increase their anion adsorption capacity. In this respect, the successful results of the production and the use of engineered biochars, such as layered double hydroxides (LDHs) functionalized biochar (LDH-biochar) and LDH-hydrochar composites have been provided. Layered double hydroxides (LDHs) are brucite-like compounds with a large specific surface area, high positive charge, and exchangeable interlayer anions. LDHs functionalized biochar and hydrochar composites are environmentally friendly adsorbents for the removal of phosphate from aqueous solutions. Also, P-loaded LDH-biochar and LDH-hydrochar composites have the potential application as a P-fertilizer. These composites may increase soil available-P through the slow release of P and can improve soil properties and fertility due to the presence of the biochar and hydrochar in their structure. So, the P-loaded LDH-biochar and LDH-hydrochar may affect the availability of soil nutrients and plant growth. Nitrogen (N), P, and potassium (K) are the macronutrients that have a direct and great influence on plants growth. Therefore, the aims of this study were: (I) producing LDH-biochar and LDH- hydrochar composites and loading them with phosphate. (II) Investigating the effects of the biochar, hydrochar, LDH, LDH-biochar, LDH-hydrochar, the P-loaded LDH-biochar (LDH-biochar-P), and LDH-hydrochar (LDH-hydrochar-P) on dry matter and concentrations of P, N, and K in corn shoot and root.

    Materials and Methods

    Biochar was produced from applewood feedstock through slow pyrolysis at 600 ºC for 1 h under Argon flow conditions. Hydrochar was produced through hydrothermal carbonization of the applewood feedstock at 180 ºC and 11 bars pressure for 12 h. Then by precipitation of LDH particles on the biochar and hydrochar surfaces, LDH-biochar and LDH-hydrochar composites were prepared. The LDH particles were synthesized via a combined fast co-precipitation and hydrothermal treatment route. Each gram of LDH-biochar and LDH-hydrochar composites was loaded with 51 and 47 mg P, respectively. Then using a factorial experiment on the basis of completely randomized design with three replications, the effects of biochar, hydrochar, LDH, LDH-biochar, LDH-hydrochar, LDH-biochar-P, and LDH-hydrochar-P were studied in presence and absence of monocalcium phosphate fertilizer on corn dry matter and concentrations of N, P, and K in corn shoot and concentrations of P and K in corn root.

    Results and Discussion

    The results showed that the biochar had a higher yield and ash percentage, pH and electrical conductivity (EC) as compared with the hydrochar. The concentrations of all studied nutrients in the biochar, except for N, were greater than those of hydrochar and biomass. The P, K, Na, Fe, Mn, and Zn concentrations in biochar and hydrochar were significantly greater than the initial biomass. The application of P-fertilizer increased root and shoot dry matters in all treatments, except for LDH-biochar-P and LDH-hydrochar-P treatments. Biochar and hydrochar had no significant effects on root and shoot dry matter in non-P-fertilized treatments and had no significant effects on P and K concentrations of corn root and shoot. However, biochar and hydrochar increased shoot dry matter in P-fertilized treatments. The highest root and shoot dry matters, P concentrations of root and shoot, and N concentration of shoot were obtained in the presence of the LDH-biochar-P and LDH-hydrochar-P, and the lowest root and shoot dry matters of corn were observed in the presence of the LDH. Application of P-fertilizer increased P concentrations of corn root and shoot in the presence of the LDH-biochar and LDH-hydrochar but decreased the K concentration of root in biochar, LDH-biochar and no amendment treatments and had no significant effects on N and K concentrations in the shoot. The application of P-fertilizer decreased P translocation factor in presence of the LDH-biochar and LDH-hydrochar and had no significant effect on P translocation factor in all other treatments. Using P-fertilizer had no significant effect on K translocation factor in all treatments. Biochar, hydrochar, LDH, LDH-biochar, and LDH-hydrochar had no significant effects on P and K translocation factors. The translocation factor of P was greater than 1 in all treatments, except for the LDH-biochar-P and LDH-hydrochar-P treatments. Also, the translocation factor of K was greater than that of P in all treatments.

    Conclusion

    Due to the structural similarities between biochar and hydrochar, LDH-biochar and LDH-hydrochar, and LDH-biochar-P and LDH-hydrochar-P, the root and shoot dry matter and concentrations of the studied elements in corn root and shoot were not significantly different between the biochar and hydrochar, LDH-biochar and LDH-hydrochar, and LDH-biochar-P and LDH-hydrochar-P treatments, respectively. P-fertilizer had synergistic relationships with biochar, hydrochar, LDH-biochar, and LDH-hydrochar but antagonistic relationships with LDH, LDH-biochar-P, and LDH-hydrochar-P composites in terms of dry matter and P concentrations in corn root and shoot. So, applications of the biochar, hydrochar, LDH-biochar, and LDH-hydrochar accompanied by P-fertilizer and the use of LDH-biochar-P and LDH-hydrochar-P without the application of P-fertilizer can be proposed for corn cultivation under similar conditions.

    Keywords: Biochar, Carbonization, Corn, Hydrochar, Layered double hydroxide, phosphorus
  • Samaneh Tajik, Shamsollah Ayoubi *, Mohmmad Mehdi Darvisihi, Hossein Khademi Pages 147-160
    Introduction

    Soil snails constitute an important part of the forest ecosystem and play an essential role in litter decomposition and soil calcium concentration. Snails are known as bioindicators because of narrow distribution, short lifetime, and high sensitivity (22, 24). The abundance and distribution of soil snails are dependent on different environmental conditions, such as precipitation, pH, soil calcium, and plant cover. Also, soil properties are mainly related to topographic parameters. Because ecosystem components have complex relationships, we need powerful models to find effective factors and spatial variations of the soil fauna (23). Linear Regression and random forest are popular and applicable models in soil science. Up to the present, no study has investigated the effect of soil parameters on snail abundance using linear regression and random forest. This study was performed to investigate the effect of soil properties and topographic parameters on the abundance of soil snails and their distribution in a part of forest area located in Bahramnia forest, an experimental site in Golestan Province, in the north of Iran.

    Materials and Methods

    This study was conducted in Shast Kalate (Bahramnia) forest, an experimental forest of Gorgan University of Agricultural Sciences and Natural Resources, located at the eastern Caspian region, north of Iran (36° 43′ 27″ N latitudes, 54°24′ 57″ E longitudes). 153 soil samples were collected from 0-10 cm; then soil snails were gathered and classified into the Gastropoda taxonomic class group. Soil properties, such as Soil particle size distribution (clay, silt, and sand), soil pH, electrical conductivity (EC), calcium carbonate equivalent (CCE), soil organic carbon (OC), total nitrogen (TN), and Soil microbial respiration (Resp), were measured via laboratory analysis. Also, digital elevation model and satellite images were used to determine the topographic parameters, such as Elevation, slope, slope aspect (Aspect), land surface temperature (land temp) wetness index (WI) and normalized difference vegetation index (NDVI). We used linear regression and nonlinear random forest models for investigating linear and nonlinear relationships between soil properties, topographic parameters, and the abundance of soil snails. Likewise, sensitive analysis was done to find the importance of the input parameters.

    Results and Discussion

    The PCA analysis showed that first and second components explain 38 and 21 percent of the variation. In the first component, EC, OC, TN, pH, and silt were the most variable, and in the second component CCE, Clay, OC, sand, and EC were the most important parameters. In both components, topographic parameters had no effect. The PCA graph showed that CCE, sand, and pH had the most correlation with snail abundance and EC, Resp, OC, and TN affected their abundance. The validation results of regression and random forest models showed that random forests have more accuracy (0.49) and low error (1.82). In addition, the sensitive analysis showed that CCE, pH, EC, OC, aspects, elevation, and land temp are the most important parameters on snail abundance. Different studies reported that pH and CCE are effective parameters on snail abundance (20, 17). Also, Ondina., et al. (27) reported that EC has an important effect on soil snail abundance. We hypothesize that topographic parameters affect soil snail nonlinearly and by affecting  soil properties. Aspect is one of the topographic parameters that, via an effect on land temperature, land cover, and pH (8), has an important role in soil snails. In this way, elevation, by affecting  pH, wetness, land temperature, OC, and TN, affects soil snail abundance (13). Land temperature is the other topographic parameter that is affected by aspect and elevation and had a significant effect on snail abundance by affecting  OC and wetness (17).

    Conclusion

    Based on the results, nonlinear random forest model had more accuracy than linear regression in predicting snail abundance. Results showed that calcium carbonate equivalent, pH, EC, and organic carbon were the most effective soil priorities on snail abundance. There was no linear relation between soil properties and soil snails, but in the nonlinear model, we found their role. Aspect, elevation, and land temperature were the most effective parameters on snail abundance that probably affected soil properties, such as calcium carbonate and soil moisture.

    Keywords: Soil properties, Topography, modeling, Regression, Random forest