Water Utilization and Economic Benefit of Wheat Multiple Cropping with Green Manure Under Nitrogen Reduction in Hexi Irrigation Area of Northwest China
[Objective]In view of the problems of excessive application of nitrogen fertilizer and lower water resource utilization efficiency and economic benefits in crop production in the irrigation area of Hexi Oasis,the aim of this study was to explore the effects of multiple green manures after wheat and moderate reduction of chemical nitrogen fertilizer on the water consumption characteristics and economic benefit of wheat field.[Method]From 2019 to 2020,a split plot experiment was conducted in the oasis irrigation area of Hexi,Gansu province.Two planting patterns were set up in the main area,namely,multiple cropping of green manure after wheat harvest(W-G)and single cropping of wheat(W).In the sub-plot,there were five nitrogen application levels,namely no nitrogen application(N0),conventional nitrogen application level 180 kg·hm-2(N4),reduced 45%nitrogen application(N1),reduced 30%nitrogen application(N2),and reduced 15%nitrogen application(N3).[Result]Grain yield of wheat and systematic biothermal energy were significantly increased by multiple green manure after wheat(W-G)and the moderate reduction of chemical nitrogen fertilizer,in 2019 and 2020,which increased by 10.8%and 12.4%,respectively,and the yield of systematic biothermal energy increased by 37.8%and 40.3%,respectively.Compared with nitrogen reduction of 15%(W-G-N3)in sole wheat and traditional nitrogen application(W-N4)in sole wheat,the grain yield increased by 6.9%-16.7%and 7.9%-13.6%,respectively,and the biothermal energy yield increased by 52.0%-62.2%and 27.1%-58.9%,respectively.The water consumption of W-G decreased by 6.3%-16.0%compared with that of W wheat growing stage,and W-G-N3 decreased the seasonal water consumption of W-N3 and W-N4 by 13.4%-20.5%and 20.8%-29.0%,respectively.Repeated planting of green manure could improve the water use efficiency of wheat,and W-G increased by 7.9%and 19.2%,respectively.In 2019,compared with W-N3 and W-N4,the WUE of W-G-N3 increased by 23.5%and 5.1%,respectively.Compared with W-N3 and W-N4,W-G-N3 could improve the energy yield of per unit water efficiency of the system,which was increased by 2.7%-14.5%and 9.3%-17.5%,respectively.Compared with the W and W-G increased the cost input,and the gross output also increased.In 2019,the net return of W-G-N3 increased by 9.8%and 9.5%compared with W-N3 and W-N4,respectively;in 2020,the net return of W-G-N3 decreased by 15.6%and 15.7%compared with W-N3 and W-N4,respectively.In 2019 and 2020,the output/input of multiple cropping green manure after wheat harvest reduced by 20.7%and 23.1%compared with sole wheat,and the output/input of W-G-N3 was 14.8%-23.1%compared with W-N3 and W-N4,and W-G reduced the benefit per cubic meter water of the system due to more resources input.[Conclusion]In the Hexi oasis irrigation areas,multiple green manure after wheat combined with moderate reduction of chemical nitrogen fertilizer could improve crop yield and economic benefit,as well as water resource utilization efficiency,among which the comprehensive effect of multiple green manure after wheat combined with 15%nitrogen treatment is outstanding,which could be used as an ideal planting pattern and nitrogen application level to improve water resource utilization and farmers'income.
green manurewheatmultiple croppingreduce nitrogen applicationyieldwater use efficiencyeconomic benefit
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