Experimental Study On The Coupling Effect Of Water And Nitrogen On Cotton Under Drip Irrigation Without Film In Southern Xinjiang

The pollution of residual film in cotton fields in Xinjiang’s cotton planting areas is becomingincreasingly severe,and white pollution has caused serious impacts on the soil environment in the areas,restricting the sustainable development of local agriculture.The cultivation technology of non film drip irrigation provides an optional way to solve this problem.However,after losing the moisture retention effect of plastic film,the risk of cotton yield reduction will increase.However,through reasonable water and nitrogen application techniques,the yield,quality,and water and nitrogen utilization efficiency of non film drip irrigation cotton can be promoted.Therefore,this experiment was conducted from April to October 2021 and 2022 at the Hydrological and Water Resources Water-saving Irrigation Experimental Station of the First Division of the Xinjiang Production and Construction Corps to conduct field experiments on water nitrogen coupling of cotton under non film drip irrigation.Two irrigation quotas W1(450 m³·hm^-2)and W2(540 m³·hm^-2)were set up in the experiment,and three nitrogen application rates F1(low nitrogen 150 kg·hm^-2),F2(medium nitrogen 225 kg·hm^-2),and F3(high nitrogen 300 kg·hm^-2)were used to explore the effects of water and nitrogen coupling on the growth physiology,nutrient absorption and utilization,soil nutrient distribution,and yield and quality of cotton under non film drip irrigation.The main research conclusions are as follows:（1）The coupling of water and nitrogen has a significant impact on soil nutrients and plant nitrogen accumulation.The accumulation of soil moisture,nitrate nitrogen,ammonium nitrogen,and plant nitrogen increased with the increase of irrigation quota.The W2 treatment increased by an average of 6.16%,7.75%,8.88%,and 25.61%compared to the W1 treatment.However,the total soil nitrogen decreased with the increase of irrigation quota,and the W2 treatment decreased by 13.29%compared to the W1 treatment.With the increase of nitrogen application rate,the accumulation of soil nitrate nitrogen,ammonium nitrogen,and plant nitrogen showed an increasing trend.F3 treatment increased by an average of 25.14%,10.56%,and 25.27%compared to F1,while soil moisture showed a decreasing trend.F3 treatment decreased by an average of 11.91%compared to F1.Under low water conditions,the total nitrogen content in the soil showed an increasing trend,with F3 treatment increasing by an average of 11.25%compared to F1,while under high water conditions,it showed a decreasing trend,with F3 treatment decreasing by an average of 16.46%compared to F1.（2）The coupling of water and nitrogen has a significant impact on the growth physiology of cotton.With the increase of irrigation quota and nitrogen application rate,cotton plant height,leaf area,leaf chlorophyll content（SPAD value）,net photosynthetic rate（Pn）,stomatal conductance（Gs）,transpiration rate（Tr）,and aboveground dry matter mass all show an increasing trend,while intercellular carbon dioxide concentration（Ci）decreases with the increase of irrigation quota.The plant height,leaf area,aboveground dry matter,and SPAD values of W2 treatment increased by 4.57%,30.79%,22.87%,and 16.66%compared to W1 treatment,while the plant height,leaf area,aboveground dry matter,and SPAD values of F3 treatment increased by 11.85%,23.33%,20.75%,and 9.81%compared to F1 treatment.（3）The coupling of water and nitrogen has a significant impact on cotton yield and quality.When the nitrogen application rate is the same,the cotton yield increases with the increase of irrigation quota,while the water use efficiency shows a decreasing trend.Under low water conditions,the cotton yield and water use efficiency increase with the increase of nitrogen application rate,while under high water conditions,they first increase and then decrease with the increase of nitrogen application rate,.The productivity of cotton with partial nitrogen fertilizer decreases with the increase of nitrogen application rate,increases with the increase of irrigation quota under low and medium nitrogen conditions,and decreases under high nitrogen conditions.The coupling effect of irrigation quota and nitrogen application rate on cotton fiber quality is not significant,but increasing irrigation quota can improve cotton fiber uniformity index,breaking strength,and elongation.Moreover,with the increase of nitrogen application rate,the average length of the upper half of cotton shows a trend of first increasing and then decreasing.In the southern Xinjiang region where water resources are scarce,the irrigation quota of 450 m³·hm^-2 and nitrogen application rate of 300 kg·hm^-2 have the best yield and highest water use efficiency,making them the most suitable water and nitrogen application rate for the growth needs of cotton under non film drip irrigation in southern Xinjiang.