华北平原氮肥周年深施对冬小麦-夏玉米轮作体系土壤氨挥发的影响

氮肥深施能有效减少土壤氨挥发，然而目前国内外关于小麦-玉米轮作体系氮肥深施缺乏周年系统性研究。本试验于2018年10月—2019年10月在中国科学院栾城农业生态系统试验站小麦-玉米轮作农田进行，利用动态箱法研究不同深施模式氨挥发损失率、氨挥发特征，旨在探讨冬小麦-夏玉米轮作体系下土壤氨排放对氮肥深施的响应，为减少农业源氨排放和优化农田施肥提供理论依据。试验设置5个处理：不施肥（CK）、常规肥料表施（T₁）、缓释肥表施（T₂）、缓释肥基追肥分层深施（T₃）、缓释肥一次性分层深施（T₄）。结果表明：氨挥发主要发生在玉米追肥季，占全年氨挥发量的84.84%；T₁、T₂、T₃和T₄处理的周年氨挥发累积量分别为22.75 kg·hm^-2、6.17 kg·hm^-2、2.25 kg·hm^-2和0.55 kg·hm^-2，分别占总施肥量的4.86%、1.32%、0.48%和0.13%。与常规肥料表施（T₁）相比，缓释肥处理（T₂、T₃和T₄）分别降低72.88%、90.11%和97.32%的氨挥发损失；一次性深施处理（T₄）能避开土壤氨高挥发期，周年氨挥发累积量与不施肥处理（0.43 kg·hm^-2）没有显著差异，且显著低于表施处理。CK、T₁、T₂、T₃和T₄全年产量分别为8.31 t·hm^-2、13.20 t·hm^-2、12.66 t·hm^-2、14.42 t·hm^-2和14.22 t·hm^-2；与常规肥料表施（T₁）相比，缓释肥深施（T₃和T₄）均可提高作物产量，分别增产9.25%和7.75%。而缓释肥表施（T₂）产量略有降低。综合考虑土壤氨排放和作物产量，缓释肥表施（T₂）可以显著降低土壤氨挥发，但是作物产量不稳定；而氮肥深施（T₃、T₄）能在保证作物高产的基础上显著降低土壤氨排放，是一种高效、简便、环境友好的施肥方式。

The effects of deep application of nitrogen fertilization on ammonia volatilization in a winter wheat/summer maize rotation system in the North China Plain

The deep application of nitrogen fertilizers can reduce soil ammonia volatilization, but no annual systematic study in a winter wheat/summer maize rotation system exists. Nitrogen fertilizer was deeply applied to soil from a winter wheat/summer maize rotation system to determine the effects on ammonia emissions and optimize farmland fertilization. Five treatments were used from October 2018 to October 2019:no fertilization (CK), conventional fertilizer surface-application (T₁), slow-release fertilizer surface-application (T₂), twice layered deep-application of slow-release fertilizer (T₃), and single layered deep-application of slow-release fertilizer (T₄). Ammonia volatilization primarily occurred in the corn top-dressing season and accounted for 84.84% of the annual ammonia volatilization. The cumulative amounts of annual ammonia volatiles were 22.75 (T₁), 6.17 (T₂), 2.25 (T₃), and 0.55 kg·hm^-2(T₄), accounting for 4.86%, 1.32%, 0.48%, and 0.16% of the total fertilizer application, respectively. The slow-release fertilizer treatments reduced the ammonia volatilization loss by 72.88% (T₂), 90.11% (T₃), and 96.30% (T₄) compared to T₁. The single deep application treatment (T₄) avoided the summertime high soil ammonia volatilization period, and the cumulative annual ammonia emissions were comparable to the unfertilized emissions (0.43 kg·hm^-2). The annual yields were 8.31 (CK), 13.20 (T₁), 12.66 (T₂), 14.42 (T₃), 14.22 (T₄) t·hm^-2; and compared with T₁, the slow-release fertilizer deep application increased the crop yield by 9.25% (T₃) and 7.75% (T₄). The surface application of slow-release fertilizer (T₂) slightly decreased the yield but significantly reduced the ammonia volatilization amount. In conclusion, the deep application of slow-release nitrogen fertilizer improved crop yield and reduced soil ammonia emissions, and was shown to be a simple, efficient, and environment-friendly fertilization method.