Effects Of Precipitation In Summer-fallow Season And Optimized Fertilization On Dryland Winter Wheat Yield And Environmental Impact

Soil water and nutrients are the main factors limiting crop growth in the Loess Plateau of China,and the differences in the spatial and temporal distribution of precipitation result in the differences in winter wheat yield and nutrient requirements for crops,thus matching fertilizer to precipitation and nutrient requirements is a major challenge for dryland.In this study,we investigated the winter wheat yield,nutrient utilization efficiency,economic benefits,environmental benefit under Nutrient Expert system(NE)and traditional fertilization(FP)treatment based on 28 field trials from2017 to 2021 in nine counties of the Weibei dryland area.Then we developed an optimized fertilization measure(ONE)for NE based on summer-fallow precipitation,in order to promote the application of NE for wheat production in the Loess Plateau.The main results are as follows:(1)The results from multi-year and multi-point field experiments showed that the winter wheat grain yield was significantly higher for NE treatment in the wet years than that in the normal or dry years,with an increase of 21% and 16%,respectively.The FP treatment had the highest wheat yield in the wet years.The harvest index of winter wheat in wet years was significantly lower than that in the normal-and dry years for NE and FP treatments,while the 1000 grain weight in wet years was significantly higher than that in the normal-and dry years.(3)N,P,K and protein contents of winter wheat grain for NE and FP treatments were not significantly different in the same precipitation years.However,the N,K,and protein contents of wheat grain for NE and FP treatments in the normal-and dry years were significantly higher than those in the wet years;the P contents of grain in the NE and FP treatments in the wet-and normal years were significantly higher than those in the dry years.There were no significant differences in the P contents of grain between the normal-and dry years.(4)The nutrient(N,P,and K)uptake in wheat shoots and nutrient requirements for 100 kg grain of winter wheat did not difference significantly between the NE and FP treatments in each precipitation year pattern,but they differed among precipitation year patterns.The nutrient uptake of N,P,and K increased in the wet years,but they did not differ in the normal-and dry years.The effect of precipitation in summer-fallow season on the nutrient requirements for 100 kg grain of winter wheat was different,i.e.,the P and K requirements increased while N requirements decreased in wet years.(5)The soil available phosphorus(AP)content in 0-20 cm soil layer at winter wheat harvest was affected by both precipitation year types and fertilization.Soil AP was significantly reduced by 34% in the NE treatment comparing with FP treatment in the wet years,while there were no significant differences in the normal-and dry years.Precipitation in the summer-fallow season can significantly reduced accumulation of soil nitrate-N in the 0-100 cm soil layer at the harvest.In addition,the accumulation of soil nitrate-N in the 0-100 cm soil layer in the NE treatment was significantly lower than that in the FP treatment in all precipitation years.(6)Greenhouse gas(GHG)emissions and reactive nitrogen losses(N losses)were significantly lower for NE treatment than that for FP treatment for three precipitation years,with an average reduction of 22.3% and 30.2%,respectively.The NE and FP treatments had the highest economic return of winter wheat in the wet years,the economic return of winter wheat for NE treatment increased by 13% comparing with FP treatment.(7)The ONE management can optimize N and P fertilizer application rates based on the summer-fallow precipitation,and significantly reduced N fertilizer input by 5.6%and 54.3% comparing with NE treatment in the normal-and dry years,respectively,and increased P fertilizer input by 28.5% in the wet years.The optimized fertilizer application rates could significantly reduce GHG emissions and N losses in the normaland dry years,with an average of 26.8% and 32.7%,respectively.Meanwhile,the optimized fertilizer application achieved fertilizer cost savings by a 15.8% and 44.5%reduction in the normal-and dry years,respectively.In conclusion,NE can reduce the inputs of N and P fertilizers,maintain wheat grain yield,reduce the environmental impact,and improve fertilizer utilization efficiency and economic income.Based on the nutrient requirement of winter wheat,precipitation in summer-fallow season,and soil nutrient changes under different precipitation years patterns,the NE optimized recommendation fertilization regime could improve the nutrient and water efficiency,reduce the environmental impact,and make it more suitable for winter wheat production in the Loess Plateau of China.