综合农艺管理对夏玉米氮效率和土壤硝态氮的影响

通过对播种方式、播种时间、施肥时期及用量和收获时间等农艺措施的优化组合，设置综合农艺管理和施氮量试验，研究了对夏玉米氮效率和土壤硝态氮积累的影响。结果表明，随着施氮量的增加，氮肥偏生产力显著提高，氮肥农学利用效率显著下降，氮素利用效率和氮收获指数先增加后降低，施氮184.5 kg hm^-2时达到最高；施氮显著提高了花前氮素积累量和0~30 cm土层硝态氮累积量；0~30 cm土层硝态氮累积量随施氮量的增加逐渐提高，即单一氮肥运筹下，氮效率不能持续提高，且土壤硝态氮积累量却因增施氮肥而逐渐升高。综合农艺管理的再高产高效处理(Opt-2)的氮肥偏生产力、氮肥农学利用效率、氮素利用效率和氮收获指数均最高；花前氮素积累量较低，收获后植株氮素积累总量高于农民习惯处理且低于超高产处理；玉米收获后，0~30 cm、30~60 cm和60~90 cm土层硝态氮累积量均低于农民习惯处理，即通过优化的综合农艺管理，夏玉米氮效率显著提高，生育期内氮素积累趋势合理，玉米收获后土壤硝态氮积累量较低。

Effects of Integrated Agronomic Practices on Nitrogen Efficiency and Soil Nitrate Nitrogen of Summer Maize

A field study with an integrated management experiment and a nitrogen (N) application rate test was conducted to explore the effects of integrated agronomic practices such as sowing methods, sowing time, fertilizers amount and applied date and harvest time on N efficiency and nitrate N of summer maize,. Results showed that, with increasing N application amount partial factor productivity of applied N increased and N fertilizer agricultural utilization efficiency decreased significantly; N use efficiency and N harvest index increased first and then decreased gradually, and both of them reached the maximum at a N application of 184.5 kg ha^-1; the N accumulation before tasseling stage and nitrate N accumulation in 0–30 cm soil increased. That means that it is difficult to realize high N efficiency and lower soil N accumulation persistently. Under integrated management of further high yield and high efficiency treatment (Opt-2), the partial factor productivity of applied N, N fertilizer agricultural utilization efficiency, N use efficiency and N harvest index all increased significantly; the N accumulation before tasseling stage was low, but the N accumulation of plants was higher than that under farmers’ traditional cultivation and lower than that under high yield treatment at harvest time; after harvesting, the nitrate N accumulation in 0–30, 30–60, and 60–90 cm soils was lower than that under farmers’ practices. Therefore the N efficiency of summer maize was increased significantly and the N accumulation trend was reasonable in growing season and the soil nitrate N accumulation was lower after harvesting when the integrating agronomic practices are performed.