تاثیر بیوچار و نیتروژن بر ماده خشک و جذب عناصر غذایی پرمصرف در گیاه کلزا در شرایط کم‌آبی در کشت گلدانی

این تحقیق با هدف بررسی تاثیر مصرف بیوچار حاصل از کاه‌ گندم (پیرولیز شده در دمای 300 درجه سلسیوس)  و نیتروژن بر جذب عناصر غذایی پرمصرف به‌وسیله گیاه کلزا (brassica napus l.‌) رقم هایولا 308 در شرایط تنش کم‌آبی در یک خاک آهکی لوم شنی و در کشت گلخانه‌ای انجام شد. آزمایش به‌صورت فاکتوریل و در قالب طرح کاملاً تصادفی با سه تکرار انجام شد. فاکتورهای آزمایش شامل ماده آلی در پنج سطح (بیوچار و کاه‌ گندم هر یک در 3 سطح صفر، 75/0 و 5/1 درصد)، کود نیتروژن در دو سطح (150 و 300 میلی‌گرم نیتروژن بر کیلوگرم خاک از منبع اوره) و رطوبت خاک در دو سطح (85 تا 100 درصد ظرفیت مزرعه‌ای به عنوان بدون تنش و 50 تا60 درصد ظرفیت مزرعه‌ای به عنوان تیمار تنش کم‌آبی) بودند. بعد از برداشت گیاه ماده خشک شاخساره و غلظت نیتروژن، فسفر، پتاسیم، کلسیم و منیزیم در شاخساره گیاه کلزا اندازه‌گیری شدند. نتایج نشان داد که با مصرف بیوچار و نیتروژن، ماده خشک شاخساره به‌طور معنادار نسبت به شاهد افزایش یافت. با این حال، بیشترین ماده خشک شاخساره در تیمار 75/0 درصد کاه گندم با مصرف 300 میلی‌گرم نیتروژن بر کیلوگرم خاک و رطوبت 85 تا 100 درصد  ظرفیت مزرعه به‌دست آمد. مصرف بیوچار سبب افزایش غلظت پتاسیم و فسفر شاخساره نسبت به تیمار بدون ماده آلی شد ولی غلظت کلسیم و منیزیم در تیمار حاوی بیوچار با تیمار بدون ماده آلی تفاوت معنادار نداشت. اعمال تنش کم‌آبی به‌دلیل کاهش ماده خشک گیاه و وقوع پدیده «اثر تغلیظ» سبب افزایش غلظت همه عناصر غذایی مورد مطالعه به‌جز کلسیم شد. با توجه به نتایج به‌دست آمده از این تحقیق گلخانه‌ای استفاده از بیوچار حاصل از کاه ‌گندم، جذب عناصر ضروری پرمصرف و رشد گیاه کلزا را افزایش داد و نقش مهمی در بهبود تحمل تنش کم‌آبی گیاه داشت. در رطوبت 85 تا 100 درصد ظرفیت مزرعه‌ای، 300 میلی‌گرم نیتروژن و در رطوبت 50 تا 65 درصد ظرفیت مزرعه‌ای، 150 میلی‌گرم نیتروژن بر کیلوگرم خاک در شرایط مشابه می‌تواند توصیه شود.

effects of biochar and nitrogen on rapeseed dry matter and macronutrients uptake under water deficit conditions in a pot culture

background and objectivesthe use of organic and slow release fertilizers is one of the methods of increasing the bioavailability and use efficiency of nitrogen in plants. biochar is a solid, carbon-rich material, obtained during thermochemical decomposition (pyrolysis) of biomass in a closed container under no or limited oxygen supply. biochar is an organic matter that improves plant growth by the water- and nutrient-holding capacity. the interest in biochar research is mostly focused on its roles in long-term carbon storage in soils, and soil fertility. strong resistance to microbial decomposition, high nutrient content such as phosphorus, potassium, calcium, and magnesium, high specific surface area, high cation exchange capacity (cec), and porosity are the outstanding properties of biochar distinguishing it from other soil amendments. nitrogen is one of the macronutrients for all plants, and its deficiency is common in arid and semi-arid calcareous soils. because most soils cannot supply sufficient amount of plant available-nitrogen, inorganic and/or organic nitrogen sources must be applied to meet plant nitrogen requirements. rapeseed (brassica napus l.) also known as rape, oilseed rape, and canola, is a bright-yellow flowering member of the family brassicaceae, cultivated mainly for its oil-rich seeds. about 90% of iran’s oil consumption is imported from abroad, and recently, the cultivation of rapeseed and attention to its nutrition have been included in the ministry of agriculture’s programs. rapeseed is known as a plant with a high nitrogen requirement. therefore, it is important to study the interaction of nitrogen with biochar in the case of rapeseed. materials and methodsthis experiment examined the interaction effects of biochar (produced by wheat straw pyrolyzed at 300 °c) and nitrogen (n) under water deficit stress on the growth and macronutrients uptake of rapeseed (brassica napus l.) cv. hyola 308 in greenhouse conditions in a calcareous sandy loam soil. a factorial experiment was done in a completely randomized design with three replicates. the applied soil was passed through a 4.76 sieve, supplied with various levels of organic matter plus inorganic nitrogen (50 mg kg-1 from ammonium sulfate source), and kept at 80-100% of field capacity (fc) moisture under greenhouse conditions for 60 days. the factors of our experiment were organic matter (biochar and wheat straw, each at three levels of 0, 0.75 and 1.5 %), nitrogen at two levels (150 and 300 mg n kg-1 as urea) and soil moisture at two levels (0.85fc-fc as without stress or optimum moisture and 0.5fc-0.6fc as water defict stress). after 90 days of plants growth, the plants were harvested and the dry matter and the concentrations of nitrogen, phosphorus, potassium, calcium, and magnesium in shoot of rapeseed plants were measured. resultsthe results showed that application of nitrogen and biochar significantly increased rapeseed shoot dry matter. in contrast, water drought stress decreased rapeseed shoot dry matter. the two-way interaction of nitrogen × moisture level was significant on the concentrations of nitrogen, calcium and magnesium in the rapeseed shoot. nitrogen and phosphorus concentrations were not significantly different between treatments containing biochar and without organic matter. biochar application increased shoot potassium concentration compared to organic-free treatments. concentrations of calcium and magnesium in the biochar containing treatments were not significantly different from those without organic matter. drought stress increased the concentration of all studied nutrients due to the concentration effect except calcium concentration in rapeseed shoot. according to the results, it can be concluded that biochar application increased studied nutrients uptake and resulted in improved rapeseed plant growth. in this greenhouse study, the highest shoot dry matter was obtained by application of wheat straw at the 0.75% level and 300 mg of nitrogen per kg of soil at the moisture level of 85 to 100% of field capacity. under 0.5fc-0.6fc and 1.5% biochar application conditions, increasing the level of nitrogen from150 mg n kg-1 to 300 mg n kg-1 soil had no significant effect on the shoot dry matter of rapeseed plant. conclusionaccording to the results of this study, the use of biochar derived from wheat straw pyrolyzed at 300 °c, increased the uptake of macronutrients by rapeseed, hyola 308 cultivar, in a sandy loam soil. biochar and wheat straw may play important roles in counteracting drought stress and improving soil fertility and canola production along with other proven benefits. under water deficit conditions, the rapeseed plant need for nitrogen fertilizer can be decreased. at moisture content of 85 to 100% of field capacity, 300 mg nitrogen and at moisture content of 50 to 65% of field capacity, 150 mg nitrogen per kilogram of soil can be recommended under similar conditions. more research is needed in this area especially under field conditions.data availability statementdata is available on reasonable request from the authors. acknowledgementsthis paper is published as a part of a m.sc thesis supported by the vice chancellor for research and technology of the university of tabriz, tabriz, iran. the authors are thankful to the university of tabriz for financial supports. conflict of interestthe authors declare no conflict of interest. ethical considerationsthe authors avoided data fabrication, falsification, plagiarism, and misconduct.