半湿润地区农田夏玉米氮肥利用率及土壤硝态氮动态变化

以土垫旱耕人为土为供试土壤，通过田间试验，研究了不同施氮量下（0、45、90、135和180 kg·hm^-2）夏玉米生育期土壤剖面NO₃^--N的变化特征、氮素利用率及施氮量与土壤NO^₃--N残留的关系.结果表明：在整个生育期内，土壤NO₃^--N含量均以0～20 cm土层最高，且施氮量越高，NO₃^--N含量也越高；0～60 cm土层NO₃^--N含量变化显著，60～100 cm土层NO₃^--N含量变化不大.夏玉米整个生育期，受玉米对氮素的需求和降雨的影响, 0～100 cm土层NO₃^--N累积量呈波动式降低趋势；当施氮量小于135 kg·hm^-2时，作物氮肥利用率随施氮量的增加而显著提高，但当施氮量超过135 kg·hm^-2时呈下降趋势. 氮肥农学利用率随施氮量的增加而减小，氮肥生理利用率随施氮量的增加而递增.土壤中残留NO₃^--N与施氮量呈极显著正线性相关关系 (R²=0.957^**，n=5)；施氮处理籽粒产量显著高于不施氮处理(P<0.05）；施氮量与籽粒产量呈极显著正线性相关关系（R²=0.934^**，n=5）.在本试验条件下，夏玉米生长季适宜施氮量为135 kg·hm^-2.该施氮水平可保证效益和环境的双赢.

Utilization rate of fertilizer N and dynamic changes of soil NO3--N in summer maize field in semi-humid area of Northwest China

A field experiment on manual loessial soil was conducted to study the dynamic changes of NO3(-)-N in soil profile, utilization rate of fertilizer N, and relationships between N application rate and soil residual N accumulation during the growth period of summer maize under different N application rates (0, 45, 90, 135, and 180 kg hm(-2)). The results showed that in the whole growth period of summer maize, the NO3(-)-N concentration in the soil profile was the highest in 0-20 cm layer, and increased with increasing N application rate. The NO3(-)-N concentration in 0-60 cm soil layer changed significantly, but no significant change was observed in 60-100 cm soil layer. In the growth season of summer maize, soil NO3(-)-N accumulation presented a fluctuated decreasing trend due to the N uptake by crop and the precipitation. The N utilization rate (NUR) increased with increasing N application rate when the application rate was less than 135 kg hm(-2), but tended to decrease when the application rate exceeded 135 kg hm(-2). With the increase of N application rate, the N agronomy efficiency (NAE) decreased but the N physiology efficiency (NPE) increased. There was a significant positive correlation between soil residual N accumulation and N application rate (R2 = 0.957**, n = 5). The grain yield under N application was significantly higher than that without N application (P <0.05), and there existed a significant positive correlation between grain yield and N application rate (R2 = 0.934**, n = 5). In our experiment, the optimal application rate of fertilizer N was 135 kg hm(-2), which could harmonize the relationship between economic benefits and environment.