春玉米冠层氮分布及氮效率对施氮量和施氮次数的响应OA

To clarify the effects of nitrogen(N)application rate and frequency on canopy nitrogen distribution and nitrogen efficiency in maize,a field experiment was conducted during 2022 to 2023 with two N application rates(270 kg·hm-2 and 360 kg·hm-2)and two application frequencies(three times and five times).The effects of these treatments on the dynamic distribution of canopy nitrogen and nitrogen efficiency in spring maize were exam-ined,together with a systematic analysis of leaf area index,specific leaf nitrogen,nitrogen depletion coefficient,and various nitrogen efficiency indices.The results showed that increasing both N rate and application frequency significantly enhanced the leaf area index and specific leaf nitrogen across all canopy layers.The treatment with 270 kg·hm-2 N applied in five applications reduced the nitrogen depletion coefficient by 1.6％to 6.2％,optimized the uniformity of canopy nitrogen distribution,and promoted nitrogen remobilization from vegetative organs to grains.Consequently,the agronomic efficiency and physiological efficiencies of nitrogen were increased by 7.2％to 21.0％and 7.1％to 19.2％,respectively,with a corresponding yield improvement of 1.4％to 5.4％.Structural equation modeling further indicated that the leaf area index of the lower canopy directly regulated specific leaf nitrogen and the nitrogen depletion coefficient,thereby enhancing nitrogen accumulation and contribution of N translocation to grain by 15.2％and 12.8％,respectively,ultimately driving the improvement of overall nitrogen efficiency.In con-clusion,the treatment with a nitrogen application rate of 270 kg·hm-2 combined with five applications significantly improved the vertical distribution of canopy nitrogen,enhanced nitrogen accumulation and translocation capacity,and increased both maize yield and nitrogen efficiency.Therefore,this treatment can be recommended as an optimal fertilization strategy for the green production of spring maize in irrigated regions.