Effects Of Planting Density And Nitrogen Application Rate On Water Use And Yield Of Cotton Under Filmless Drip Irrigation

In Xinjiang,drip irrigation mode of cotton under mulch has caused increasing amount of residual film in farmland,and the pollution of residual film has seriously affected the sustainable development of local agriculture.In order to solve this problem,this paper carried out field experiments on the interaction between planting density and nitrogen application rate of cotton under mulch drip irrigation in the irrigation experimental base of the First Division of Xinjiang Production and Construction Corps.The row spacing D1=30cm(3.3×10~5 plants/hm~2),D2=40cm(2.4×10~5 plants/hm~2),and the nitrogen application rate N1=210kg/hm~2,N2=285kg/hm~2,and N3=360kg/hm~2 were set at three levels.The main research results are as follows:(1)Planting density and nitrogen application rate had significant effects on cotton growth.Planting density increase when the cotton plant height,stem diameter and leaf area per plant overall showed a decrease trend,showed increasing trend,the application of increasing nitrogen when planting densities and n application rates increase aboveground dry matter showed increasing trend,but the planting densities and n application rate is too high will lead to excessive vegetative organs development at the same time,the distribution of the reproductive organs was down.The increase of nitrogen application rate resulted in an increase of net photosynthetic rate,and N2 and N3 treatments increased by 9.7%and 17.4%on average compared with N1 treatments at bud stage,while the increase of planting density resulted in a decrease of net photosynthetic rate,and D1 treatment decreased by 5.5%on average compared with D2 treatment.(2)Planting density and nitrogen application rate had significant effects on soil water content and total nitrogen content.Soil moisture content decreased with the increase of planting density and nitrogen application rate.Soil content increased with the increase of nitrogen application rate and decreased with the increase of planting density.The soil moisture content was the highest in 40～60cm soil layer,and the soil total nitrogen content was the highest in 0～20cm soil layer.With the increase of nitrogen application rate,the area with high soil total nitrogen content had a downward trend.(3)Planting density and nitrogen application rate had significant effects on cotton yield composition and fiber quality.Increasing planting density could increase boll number and fiber length per unit area,but single boll weight and seed cotton yield decreased.With the increase of nitrogen application rate,the single boll weight,seed cotton yield,fiber length in upper half,breaking strength and micronaire value all increased first and then decreased.Under dense nitrogen interaction,the seed cotton yield under D2N2 treatment reached the maximum value,which was 5350.6 kg/hm~2.(4)Planting density and nitrogen application rate had significant effects on water and nitrogen use efficiency of cotton.Planting density increases,the cotton IWUE(irrigation water use efficiency)and NPFP(nitrogen partial productivity)showed a decrease trend,the increase of n application in IWUE showed the trend of increase after decreases first,NPFP showed a downward trend,appropriate increase the nitrogen content can improve cotton IWUE,although the increase of n application increased the production within a certain scope,But it reduced NPFP.In this experiment,under the interaction of density,IWUE in D2N2treatment showed a maximum value,and NPFP in D2N1 treatment showed a maximum value.