| How to optimize the fertilization method to improve the wheat yield and water and fertilizer utilization efficiency is the key problem that needs to be solved urgently to realize the sustainable development of agriculture.Applying fertilizers to the soil at a suitable depth can not only ameliora wheat yield,but also reduce nutrient loss,conserve resources and protect the environment.In addition,the inter-annual precipitation varies greatly,and precipitation has a significant impact on soil mineral element transport and crop nutrient utilization.However,little is known about the effect of fertilization depth on wheat yield formation and water and fertilizer utilization under different precipitation.In order to give full play to the yield-increasing potential of fertilization technology under different precipitation years,this experiment was performed at the Institute of Water-Saving Agriculture in Arid Areas of Northwest A&F University from September 2019 to June 2021.The experiment set up three precipitation levels: lack of water.125 mm in a year(T1),200 mm in a normal year(T2)and 275 mm in a wet year(T3),each precipitation has 4fertilization depths: 5 cm(D5),15 cm(D15),25 cm(D25),35 cm(D35).By analyzing the influence of fertilization depth on soil moisture,nutrients,growth and yield of winter wheat under different precipitation,the regulatory effect of changing fertilization depth on winter wheat growth and water and fertilizer utilization under different precipitation was clarified.The research results can provide scientific basis and technical support for formulating fertilization strategies for winter wheat under different precipitation years.The major findings are as follows:(1)The fertilization depth range under different precipitation years had a significant effect on the growth indexes of winter wheat.In water-deficient years,the plant height and leaf area index of D35 treatment were significantly higher than those of D5,D15 and D25,respectively.Compared with D5 and D15,the dry matter accumulation at maturity in D35 treatment increased significantly by 27.86% and 13.66%,respectively,and increased by5.26% compared with D25 treatment.In a normal year,the plant height at the mature stage of the D25 treatment was significantly increased by 2.58%,2.58% and 4.59%,the dry matter accumulation was significantly increased by 16.18%,3.83% and 18.55%,and the leaf area index was significantly increased by 62.44% compared with the D35,D15 and D5 treatments,respectively.%,30.57% and 49.78%.In wet years,the plant height at the mature stage of the D15 treatment was significantly increased by 5.41% and 5.73%,the leaf area index was significantly increased by 11% and 43.47%,and the dry matter accumulation was significantly increased by 13.21% and 18.55% compared with the D25 and D35 treatments,respectively.Significant differences in plant height,leaf area index and dry matter accumulation between D5 treatment and D15 treatment are negligible.(2)The fertilization depth had a significant effect on the number of spikes,grains per spike and yield of winter wheat under different precipitation,but had less effect on the1000-grain weight.In dry years,the yield of D35 treatment was significantly increased by25.08% and 12.26% compared with D5 and D15 treatments,respectively,and 3.31% higher than that of D25 treatment.In normal water years,the yield of D25 treatment was significantly increased by 18.66%,4.04% and 17.48% compared with D5,D15 and D35 treatments,respectively.In wet years,the yield,panicle number and grain number per spike of D15 treatment were significantly higher than those of D25 and D35 treatments,and the yield of D15 treatment was significantly higher than that of D25 and D35 treatments by9.83% and 14.76%,respectively(p<0.05),an increase of 1.10% compared with D5 treatment,and there was no significant difference between the two.(3)Different fertilization depths had different effects on water use efficiency of winter wheat under different precipitation.In years of lack of water,compared with D5 treatment,other treatments reduced the average soil water content in the 0-200 cm soil layer by1.54%-7.36%;improved water consumption and water use efficiency,D15,D25 and D35 treatments Water consumption was significantly increased by 2.86%,7.38% and 6.03%,and water use efficiency was increased by 8.56%,14.23% and 16.57%,respectively,and there was no significant difference between D25 and D35 treatments.In normal water years,compared with other treatments,D25 treatment reduced the average soil water content in the0-200 cm soil layer.Compared with D5 and D35 treatments,D25 treatment significantly increased water consumption by 5.96% and 4.32%,respectively.D15 and D25 treatments significantly improved by 12.02%,12.02% and 12.35%,respectively.In wet years,the average water content of the 0-200 cm soil layer in the D15 treatment was lower than that of the other treatments,the water consumption of the D25 and D35 treatments was significantly increased by 2% and 6.45%,respectively,and the water use efficiency was increased by6.67% and 6.89%,respectively,which show few significant differences compared with D5 treatment.(4)No matter what kind of precipitation year,the nitrate nitrogen content in the 0-100 cm soil layer showed a decreasing trend with the deepening of the soil layer depth.Under the same precipitation year,the soil nitrate nitrogen content of all deep application treatments was significantly higher than that of surface application treatments,and deep application promoted soil nitrate nitrogen accumulation.In the soil layer of 0-20 cm in dry years,normal water years and wet years,D5 has the highest nitrate nitrogen content;20-40 cm soil layer,D25 soil nitrate content is the highest;40-100 cm soil layer,The soil nitrate nitrogen content was the highest in D35.(5)The nitrogen uptake of winter wheat in wet years increased by 26.17% and 6.8%respectively compared with those in low water years and flat water years.Appropriate fertilization depth under different precipitation can promote the absorption of nutrients by crops.In the lack of water years,the nitrogen uptake of D35 treatment was significantly increased by 18.67% and 8% compared with D5 and D15 treatments,and 1.13% higher than that of D25 treatment.In normal water years,the nitrogen uptake of D25 treatment was the largest,which was significantly increased by 10.36%,3.17% and 9.43% compared with D5,D15 and D35 treatments,respectively.In wet years,the nitrogen uptake of D15 treatment was significantly higher than that of D25(6.44%)and D35(9.52%)treatments,while no significant difference was shown with D5 treatment.(6)The responses of nitrogen fertilizer yield contribution rate,nitrogen fertilizer partial productivity and nitrogen recovery efficiency to fertilization depth showed a consistent law under different precipitation.The nitrogen recovery efficiency of D35 treatment was 40.36%in the water shortage year,which was respectively improved by16.65 percentage points and7.84 percentage points comparing with D5 and D15 treatments,as well as 1.18 percentage points impeoved in contrast to D25 treatment.In a normal year,the nitrogen recovery efficiency of D25 treatment was 36.75%,comparing with D5,D15 and D35 treatments it was significantly imprroved by 11.63 percentage points,3.16 percentage points and 10.68 percentage points,respectively.In wet years,the nitrogen recovery efficiency of D15 treatment was 33.20%,which signicificantly increased 7.91 percentage points and 11.37 percentage points than that of D25 and D35 treatments,respectively,as well as 1.18 percentage points increased in contrast to D5 treatment.The comprehensive analysis of the two-year experimental results showed that the appropriate fertilization depth under different precipitation can enhance the absorption and utilization of nutrients by winter wheat,promote the growth and development of crops,and thus improve the yield and water and fertilizer utilization efficiency of winter wheat.On the whole,under different precipitation years,the optimal yield appeared at different fertilization depths,which were T1D35,T2D25 and T3D15,respectively. |
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