[Effects of combined application of chemical fertilizer and organic manure on wheat yield and leaching of residual nitrate-N in dryland soil].

The effects of optimum nitrogen (N) fertilization rate with and without adding manure on wheat yield and leaching of residual nitrate-N in soil profile were examined in Weibei dryland, Shaanxi with a field experiment combined different N fertilization rates (0, 75, 150, 225, 300 kg N·hm-2) and organic manure (0 and 30 t·hm-2). The results showed that, compared to chemical N fertilizer, combined application of inorganic fertilizer and organic manure increased winter wheat yield by 14.7% when N fertilization rate was reduced by 27.1%. The highest yield was obtained when 150 kg·hm-2 of N rate was combined with the manure (N150+M). The combination of N fertilizer and manure promoted N uptake of wheat grain and increased N use efficiency by 20.2%. The highest N use efficiency was recorded in the N150+M treatment. In addition, the lea-ching of residual nitrate-N during the wheat growing season and the leaching of nitrate-N during summer fallow were decreased. When N application rate was lower than 115 kg·hm-2, N fertilizer combined with organic manure reduced the amount of nitrate-N leaching in summer fallow. We recommend the combined application of organic manure with about 150 kg·hm-2 of N fertilizers in Weibei dryland to guarantee high winter wheat yield, N use efficiency, and reduce excessive residue of fertilizer N in the soil.针对渭北旱塬氮肥施用不合理的问题,通过不同氮肥用量(0、75、150、225、300 kg N·hm-2)与有机肥(30 t·hm-2)配施,明确渭北旱塬麦田配施有机肥条件下合理的氮肥用量以及配施有机肥的减氮增产作用和对硝态氮残留淋失的影响.结果表明: 与单施化肥处理相比,有机无机肥配施可以在减少27.1%的氮肥用量情况下,提高14.7%的小麦籽粒产量,其中,施氮量150 kg·hm-2配施有机肥处理的产量最高;有机无机肥配施可以促进小麦籽粒氮素吸收,氮肥利用率提高20.2%,尤其当氮肥用量为150 kg·hm-2时,氮肥利用率达到最高值(42.0%);配施有机肥还能减少氮肥当季残留量和小麦生育期硝态氮向深层土壤淋溶,降低夏闲期淋失层硝态氮的淋失比例,当施氮量低于115 kg·hm-2时,配施有机肥可以降低夏闲期硝态氮淋失量.基于本研究,推荐渭北旱塬在配施有机肥30 t·hm-2的基础上,氮肥用量150 kg·hm-2左右可实现小麦高产,提高氮肥利用率,防止氮肥过量残留.