Effects Of Coupling Of Water And Nitrogen As Well As Planting Density On Growth And Water-Nitrogen Utilization Of Spring Maize In Hexi Areas With Drip Fertigation

In order to solve the problems of water resource shortage and low efficiency of water and fertilizer utilization in Hexi region based on the technology of water and fertilizer integration under mulch drip irrigation,the effects of planting density and water nitrogen interaction on the growth,yield and water nitrogen utilization efficiency of spring maize were studied.To explore the planting density and water and nitrogen utilization model of spring maize for water-saving,fertilizer saving and efficient production.In this experiment,there were 16treatments including 2 planting densities D₈（80000 plants/hm²）,D₁₀（100000 plants/hm²）,2irrigation levels W₈₀（80%ET_C）,W₁₀₀（100%ET_C）and 4 nitrogen application levels N₀（0kg/hm²）,N₁₂₀（120kg/hm²）,N₁₈₀（180kg/hm²）and N₂₄₀（240kg/hm²）.The plant height,stem diameter and leaf area of spring maize were observed and recorded in the growth period.The dry matter accumulation,yield and its components,soil nitrate nitrogen residue were collected and counted,and the water use efficiency and nitrogen use efficiency were measured and calculated.The experimental results are as follows:（1）Planting density,irrigation and nitrogen application had significant effects on the growth index and dry matter accumulation of Spring Maize（P<0.05）.High density planting increased the dry matter accumulation of crop population.Under the density of D₂（100000plants/hm²）,the dry matter accumulation of W₁₀₀D₁₀N₂₄₀ treatment was 5.9%and 14.7%higher than that of W₈₀D₁₀N₂₄₀ and W₈₀D₁₀N₁₈₀respectively.（2）Under the same irrigation and nitrogen application,the yield of spring maize increased with the increase of planting density.The highest yield of W₁₀₀D₁₀N₂₄₀ was17614kg/hm².Compared with W₁₀₀D₁₀N₁₈₀,W₈₀D₁₀N₁₈₀ and W₈₀D₁₀N₂₄₀,the yield of spring maize increased by 5.7%,6.7%and 5.8%respectively,but there was no significant difference among the three treatments（P<0.05）.Therefore,under the condition of high nitrogen application and high density,the increase of irrigation from 80%ET_Cto 100%ET_Chad little effect on the yield.（3）Planting density,irrigation and nitrogen application had significant effects on WUE and IWUE（P<0.01）.Under the same irrigation and nitrogen application,WUE of spring maize increased significantly with the increase of planting density,and got higher WUE value under W₁₀₀D₁₀N₂₄₀,W₁₀₀D₁₀N₁₈₀ and W₈₀D₁₀N₁₈₀treatments.The irrigation water use efficiency of spring maize reaches the maximum value in W₈₀irrigation level,D₁₀ planting density and N₁₈₀-N₂₄₀ kg/hm² nitrogen application range.（4）Planting density,irrigation and nitrogen application had significant effects on nitrogen absorption and utilization of spring maize.Under the same irrigation and nitrogen application conditions,the total nitrogen uptake and accumulation,nitrogen use efficiency and Nitrogen Agronomic use efficiency of spring maize increased with the increase of planting density.With the same amount of irrigation,the accumulation of nitrogen uptake increased with the increase of nitrogen application,but the nitroge n use efficiency and agronomic nitrogen use efficiency decreased with the increase of nitrogen application.It showed inverse relationship and decreased with the increase of nitrogen application.The NPFP value of spring maize decreased with the increase o f nitrogen application.The NPFP value of W₁₀₀D₁₀N₂₄₀was significantly lower than that of W₁₀₀D₁₀N₁₈₀ and W₈₀D₁₀N₁₈₀,but there was no significant difference between W₁₀₀D₁₀N₁₈₀and W₈₀D₁₀N₁₈₀（P>0.05）.Therefore,the application of nitrogen in the range o f 180-240kg/hm² can harvest higher total nitrogen absorption and accumulation,and the planting density of 100000 plants/hm² can harvest better nitrogen utilization efficiency and partial nitrogen production,while the nitrogen utilization efficiency and total nitrogen absorption and accumulation of 80%ET_Cirrigation and 100%ET_Cirrigation under the condition of high density and high nitrogen application are not significantly different.Considering water saving,irrigation is set at 80%ET_C.（5）The nitrate nitrogen residue in the root zone of spring maize increased with the increase of nitrogen application,and decreased with the increase of irrigation water and planting density.After harvest,a large amount of nitrate nitrogen accumulated at 40-60cm of the root soil layer of W₂ irrigation treatment and moved to 60cm-100cm soil layer.However,with the increase of planting density,the residual nitrate nitrogen in the soil is mostly concentrated in the 0-60cm soil layer,which is not only conducive to the growth and utilization of crops in the next season,but also can reduce the deep regional water and soil pollution.（6）From the point of view of economic high yield,efficient utilization of water and fertilizer and reduction of nitrogen leaching loss,the suitable planting density of spring maize under film drip fertilization in Hexi area is 100000 plants/hm²,the amount of nitrogen application is 180-240 kg/hm²,and the amount of irrigation is 80%ET_C.