华北平原冬小麦/夏玉米轮作体系对氮素环境承受力分析

Analysis of environmental endurance of winter wheat/summer maize rotation system to nitrogen in North China Plain

通过田间试验研究了华北地区冬小麦/夏玉米轮作体系对氮素的环境承受力。结果表明,冬小麦和夏玉米达到最高产量时的施氮量分别是112和180 kg/hm2。氮肥利用率和农学利用率随施氮量的增加而降低,生理利用率表现出抛物线的趋势。在农户习惯施氮条件下,冬小麦和夏玉米的氮肥利用率分别是10%和6%,每千克氮肥分别增产2和3千克。灌水和集中降雨是引起土壤硝态氮明显下移的主要因素。氮素平衡计算的结果表明,低施氮量时,氮素盈余以残留Nmin为主,高量施氮则以表观损失为主。将收获后0—90 cm土壤中的硝态氮的量控制到150kg/hm2,可以在兼顾环境的前提下获得较高的产量;此时冬小麦季的施氮量是122 kg/hm2,产量(干物重)达到最高产量4331 kg/hm2;夏玉米季的施氮量是145 kg/hm2,产量(干物重)是7965 kg/hm2,达到最高产量的97%。

A field experiment was conducted to study the environmental endurance in winter wheat and summer maize rotation system to nitrogen under current high soil nitrogen fertility of North China Plain. Results showed that the yield of winter wheat and summer maize would reach maximum with the N application rate being 112 kg/ha and 180 kg/ha respectively. With the increment of nitrogen application rates, recovery efficiency and agronomic efficiency of nitrogen fertilizer decreased , while physiological efficiency showed a parabola trend. Under conventional nitrogen application rates, recovery efficiency of nitrogen fertilizer in winter wheat and summer maize were 10% and 6%, respectively and the yields increment per kilogram nitrogen fertilizer were 2 kilogram and 3 kilogram respectively for winter wheat and summer maize. Intensive irrigation and concentrated rainfall were the dominant factors causing soil nitrate-N moving downward obviously. Results of nitrogen balance calculation indicated that nitrogen surplus was primarily existed with Nmin at low nitrogen application rate, while was primarily apparent loss at high nitrogen application rate treatments. The amount of accumulated nitrate-N in 0-90cm soil profile after harvest below 150 kg/ha could be right amount of N to optimize crop yield while minimizing loss of N to the environment. That means the recommended nitrogen application rate for winter wheat was 122 kg/ha and for summer maize was 145 kg/ha.