连续秸秆还田条件下陇东旱地玉米高产高效及土壤培肥的氮肥减施策略OA

[Objectives]Nitrogen application can effectively enhance soil fertility and nutrient availability,and maintain high and stable crop yield.We studied the effects of full and reduced nitrogen application rates on dryland maize yield,water use efficiency(WUE),and soil fertility indicators under continuous straw incorporation in Loess Plateau of Eastern Gansu Province,to provide a basis for optimizing nitrogen fertilizer management in the region.[Methods]A field experiment was initiated in 2021 at the Zhenyuan Experimental Station,Gansu Agricultural Academy.The tested maize cultivar was Xianyu 335.The conventional nitrogen application rate(N 225 kg/hm2)was defined as 100%N.Five treatments were set up:full N rate without straw return(N);under an annual straw return of 9000 kg/hm2,application of 100%,80%,and 60%of the full N rate,denoted as NS,80%NS,and 60%NS,respectively;and a control without N application or straw return(ck).0-40 cm soil samples were collected after harvest to determine soil organic matter,total and available N,P,and K,microbial biomass nitrogen content(MBN),and enzyme activities.maize yield and its components were investigated,and water use efficiency was calculated over four consecutive years.[Results]Compared with the CK treatment,the combined application of straw return and nitrogen fertilizer significantly increased maize yield and WUE by 68.0%-91.8%and 68.8%-89.4%,respectively.Kernels per ear and 100-kernel weight increased by 30.2%-35.5%and 9.2%-48.7%,respectively.In the 0-40 cm soil layer,soil organic matter,total N,available N,and microbial biomass nitrogen increased by 17.0%,24.0%,32.4%,and 17.6%,respectively.in the surface 0-5 cm soil layer,nitrate reductase,nitrite reductase,and urease activities by 6.1%,22.2%,and 6.8%,respectively.Compared with the NS treatment,the 80%NS treatment significantly increased yield and WUE by 14.0%and 13.2%in 2021;showed no significant effect on yield but increased WUE by 8.8%in 2022;decreased yield and WUE by 9.9%and 11.2%in 2023;and showed no significant differences in 2024.The N treatment achieved similar cumulative yield comparable to NS and 80%NS and also improved soil fertility.Except for 2022,the 60%NS treatment resulted in significantly lower yield and WUE than NS treatment and reduced soil total N,total P,available N,available P,and microbial biomass nitrogen.Compared to the NS treatment,the 80%NS treatment reduced the average contents of total P,available P,and available N in the 0-40 cm soil layer by 8.4%,9.1%,and 15.9%,respectively,but significantly increased the average microbial biomass nitrogen content by 7.5%.Structural equation modeling(SEM)revealed that microbial biomass nitrogen,total N,and available N are key drivers of maize yield.[Conclusion]Under continuous straw return in the Longdong dryland region,full-rate nitrogen fertilizer application can achieve high and stable maize yield while maintaining and enhancing soil fertility.A 20%reduction in N application(180 kg/hm2)every two years can significantly increase maize yield and water-fertilizer use efficiency,improve soil organic matter and total nitrogen content,without reducing soil available nitrogen and phosphorus levels,thereby avoiding the risks of yield decline and soil fertility reduction associated with nitrogen reduction.Given local environmental and soil conditions,it is not recommended to exceed a 20%reduction in nitrogen application.