اثر روش كاشت پشته مرتفع و نيتروژن بر شاخص‌هاي كارايي نيتروژن و عملكرد گندم

Effects of Raised Bed Planting and Nitrogen on Nitrogen Efficiency Indices and Yield of Wheat

این آزمایش با هدف بررسی اثر كاشت پشته مرتفع و سطوح اوره بر شاخص‌های كارایی نیتروژن، عملكرد كمی و محتوای نیتروژن گندم در مزرعه تحقیقاتی دانشكده كشاورزی دانشگاه فردوسی مشهد به‌صورت كرت‌های خرد شده در قالب طرح پایه بلوك‌های كامل تصادفی با سه تكرار طی سال زراعی 95-1394 انجام شد. دو روش كاشت (مرسوم و پشته مرتفع) و پنج سطح صفر، 100، 200، 300 و 400 كیلوگرم اوره در هكتار به‌ترتیب به‌عنوان عامل‌های اصلی و فرعی مدنظر قرار گرفتند. صفات مورد مطالعه شامل عملكرد دانه، عملكرد بیولوژیك، محتوی نیتروژن دانه و كاه و شاخص‌های كارایی نیتروژن (جذب، تبدیل و مصرف) بودند. نتایج نشان داد كه اثر ساده و متقابل روش كاشت و كود اوره بر عملكرد دانه و بیولوژیك، محتوی نیتروژن دانه و كاه، كارایی جذب، تبدیل و مصرف نیتروژن معنی‌دار (05/0≥p) بود. بالاترین و پایین‌ترین كارایی جذب نیتروژن به‌ترتیب برای تیمار پشته مرتفع و بدون مصرف نیتروژن (45/0 كیلوگرم نیتروژن گیاه بر كیلوگرم نیتروژن خاك) و روش رایج و 400 كیلوگرم اوره در هكتار (14/0 كیلوگرم نیتروژن گیاه بر كیلوگرم نیتروژن خاك) به‌دست آمد. شاخص‌های كارایی جذب و مصرف نیتروژن در روش پشته مرتفع بالاتر از روش رایج بود. بیشترین و كمترین كارایی مصرف نیتروژن به‌ترتیب مربوط به تیمارهای پشته مرتفع و شاهد (65/36 كیلوگرم نیتروژن دانه بر كیلوگرم نیتروژن گیاه) و روش رایج و 400 كیلوگرم اوره در هكتار (63/10 كیلوگرم نیتروژن دانه بر كیلوگرم نیتروژن گیاه) بود. با افزایش مصرف اوره از صفر به 400 كیلوگرم در هكتار، كارایی مصرف نیتروژن 62 درصد كاهش یافت.

Introduction Nitrogen use efficiency (NUE) for wheat is only about 30%, but with best management practices it can be improved to higher levels. Optimal nitrogen (N) management is essential for maximum NUE, crop yield and minimum environmental impacts. Applying less N may result in lower grain yields and reduced grain quality. However, higher N application can result in reducing NUE and increasing fertilizer losses. Efficient use of applied N fertilizer improves crop yield and decreases the production cost. N application and recovery efficiencies depend on soil criterias; method and rate of fertilizer application; and planting methods. Improving NUE is one ecological approach for producing higher grain yield. In recent years, some researchers found that suitable management and adoption of appropriate practices could improve agricultural nitrogen use efficiency and crops production would be more efficient. Raised bed planting has shown to improve water distribution and efficiency, fertilizer use efficiency, reduced crop lodging and decreased seed rate without sacrificing yield. Planting methods could also affect the vertical distribution of leaf area index and radiation use efficiency of wheat. The objectives of this study were to determine the effects of raised bed planting and Urea fertilizer levels on the nitrogen efficiency indices and yield of wheat. Materials and Methods This experiment was conducted as split plot based on a randomized complete block design with three replications at the Agricultural Research Field, Ferdowsi University of Mashhad during the growing season of 2015-2016. The main and sub factors were allocated to planting methods (raised bed and conventional methods) and Urea rates such as 0, 100, 200, 300 and 400 kg Urea ha-1, respectively. Investigated traits were grain yield, biological yield, nitrogen content of grain, nitrogen content of straw, and efficiency indices of nitrogen (nitrogen uptake efficiency, nitrogen utilization efficiency and NUE). The treatments were run as an analysis of variance (ANOVA) to determine if significant differences existed among treatments means. Multiple comparison tests were conducted for significant effects using the LSD test. Results and Discussion Results showed that the simple and interaction effects of planting methods and Urea rates were significant (p≤0.05) on grain yield, biological yield, grain nitrogen content, straw nitrogen content, nitrogen uptake efficiency, nitrogen utilization efficiency and NUE of wheat. The maximum and minimum grain yield were observed with raised bed planting and 300 kg Urea ha-1 (7545 kg ha-1) and conventional planting and control (3865 kg ha-1), respectively. The maximum and the minimum amounts of nitrogen uptake efficiency were belonged to raised bed planting and control (0.45 kg N in plant per kg N in soil) conventional planting and 400 kg Urea ha-1 (0.14 kg N in plant per kg N in soil), respectively. The highest and lowest NUE were related to raised bed planting and control (36.65 kg N in grain per kg N in plant) conventional planting and 400 kg Urea ha-1 (10.63 kg N in grain per kg N in plant), respectively. Increasing in Urea rate from 0 to 400 kg ha-1 fertilizer decreased nitrogen use efficiency up to 62 percent. Conclusions Results showed a higher grain yield and biological yield from planting on raised bed compared with the conventional planting, owing to higher nitrogen uptake and nitrogen use efficiency. Biological yield was significantly influenced and higher trend was found with higher dose of nitrogen. There was a trend to improve grain yield with the increase of Urea levels. Grain yield increased in raised bed planting method compared with conventional planting mostly due to more fertile topsoil on the raised beds. Enhancing nitrogen fertilizer led to improve in grain yield and a decrease in NUE. Acknowledgement This research (37623.2) was funded by Vice Chancellor for Research of Ferdowsi University of Mashhad, which is hereby acknowledged.