بررسی تلفات نیتروژن، عملکرد و اجزای عملکرد ذرت تحت سطوح مختلف کود نیتروژن و مدیریت کود- آبیاری در آبیاری جویچه‌ای

پژوهش حاضر با هدف بررسی کود- آبیاری بر رشد گیاه ذرت و تلفات نیتروژن تحت مقادیر مختلف و تقسیط کود نیتروژن در موسسه تحقیقات اصلاح و تهیه نهال و بذر کرج با دو عامل مقدار کود (n1:100، n2:80 و n3:60 درصد نیتروژن خالص مورد نیاز براساس توصیه کودی) و زمان تقسیط (t1: چهار و t2: سه تقسیط مساوی) در سه تکرار و در دو سال زراعی انجام شد. سپس این تیمارها با تیمار شاهد (کوددهی عرف منطقه) مقایسه شدند. بیش‌ترین عملکرد دانه در سال نخست در تیمارهای t1n1، t1n3 و شاهد به‌دست آمد. عملکرد دانه در تیمارهای با سه تقسیط (t2) کم‌تر از چهار تقسیط (t1) بود. تقسیط نیتروژن در سه مرحله (تیمار t2) نسبت به تقسیط آن در چهار مرحله (تیمار t1) سبب کاهش نیتروژن و پروتئین دانه به‌ترتیب به‌میزان 12/8 و 13 درصد شد. تقسیط کود نیتروژن در سه مرحله سبب جذب بیش‌تر نیتروژن توسط برگ گیاه در انتهای فصل رشد شد؛ گرچه این کار اثری بر افزایش عملکرد و صفات کیفی دانه نداشت. به‌جز شاهد، تغییرات محسوسی در درصد نیتروژن خاک از سطح به عمق مشاهده نشد. بیش‌ترین درصد نیتروژن خاک در دو لایه 20-0 و 40-20 سانتی‌متر برای شاهد مشاهده شد. بیش‌ترین و کم‌ترین تلفات نیتروژن در رواناب به‌ترتیب در تیمار t1n1 (23 درصد) و شاهد (7 درصد) مشاهده شد. براساس کلیه نتایج، t1n2 به‌دلیل مطلوب‌بودن عملکرد دانه، صفات کیفی و کاهش تلفات نیتروژن به‌عنوان تیمار مناسب پیشنهاد می‌شود.

investigation of nitrogen losses, corn yield and yield components under different amounts of nitrogen fertilizer and fertigation management via furrow irrigation

the present study was conducted in the research field of seed and plant improvement research institute to investigate the effect of fertilizer amount in three levels (n1: 100, n2: 80, n3: 60 percent of fertilizer requirement) and two splitting methods (t1: four equal usage including 4-6 leaf stage, 10 leaf stage, reproduction stage and inoculation stage and t2: three equal usage including 4-6 leaf stage, 10 leaf stage and reproduction stage) on corn yield and yield components. the treatments were compared with control which is the common fertilizer usage in the region. based on the results, the highest grain yield in the first year was obtained in t1n1, t1n3 and control treatments. grain yield in t2 was less than t1. nitrogen splitting in t2 compared to t1 reduced the nitrogen content and grain protein content by 12.8% and 13%, respectively. splitting of nitrogen fertilizer in three stages caused more nitrogen uptake by crop leaves at the end of the growing season; however, this did not increase grain yield and seed quality. except for the control, no significant changes in soil nitrogen content were observed from surface to depth. the highest percentage of soil nitrogen was observed in the two layers of 0-20 and 20-40 cm in the control. the lowest content of soil nitrogen was observed in in t2n3 treatment with 24.5% (0-20 cm) and 24.5% (20-40 cm) more than control, respectively. the highest and lowest nitrogen losses in runoff were observed in t1n1 (23%) and control (7%), respectively. with the reduction of fertilizer application, runoff losses also decreased; in the t1n2 and t1n3 treatments, this reduction was 9% and 14%, respectively. overall, t1n2 is recommended as a suitable treatment due to the high grain yield, seed quality and reduction of nitrogen losses. background and objectives: although reducing the amount of nitrogen fertilizer can lessen the negative effects of its losses, but it reduces the yield and yield components of crops, including corn (1). therefore, nitrogen splitting is considered as a suitable solution to combat the reduction of nitrogen fertilizer consumption (2). corn is one of the most important grains in the world, which can be cultivated in most regions of the world. as the third most consumed grain in the world, this crop has a share of about 2.8% of grain consumption in the world. this crop is cultivated in most provinces of the country and is sensitive to nitrogen (3) consumption. increasing available nitrogen improves seed yield and growth indicators. methods: to achieve this goal, the present study was carried out in the research field of seed and plant improvement research institute on fertilizer amount in three levels (n1: 100, n2: 80, n3: 60 percent of fertilizer requirement) and two splitting methods (t1: four equal usage including 4-6 leaf stage, 10 leaf stage, reproduction stage and inoculation stage and t2: three equal usage including 4-6 leaf stage, 10 leaf stage and reproduction stage) in two years. these treatments were compared with control which was the traditional fertilizer usage in the region. the planting operation of this variety was done in may every year with a density of 80 thousand plants per hectare. irrigation was done based on the complete water requirement of the plant. to determine the amount of irrigation water, evaporation from the surface of class a pan and application of pan and plant coefficients were considered. irrigation was done in the form of furrows and according to the custom of the region, with a cycle of seven days. for this purpose, five wells were considered for each treatment. three middle furrows were considered for harvest and two side furrows were considered for the marginal effect. the distance between the stacks was 75 cm and their length were 115 meters. irrigation treatments were applied 5 days