Study On Cotton Growth Charcteristics And Regulation Method Under Film-mulched Drip Irrigation With Ionized Brackish Water

The utilization of brackish water resources is of great significance for alleviating freshwater scarcity,improving an dutilizing saline-alkali land,especially Xin Jiang.Xin Jiang is a typical inland arid region with a lack of freshwater resources,poor soil fertility,and widespread distribution of saline-alkali land,which are key factors limiting agricultural development.However,the use of brackish water for irrigation can easily lead to reduced crop yields and secondary soil salinization.Cotton is the world’s most important fiber and oil crop,accounting for 35%of the world’s total fiber consumption.It is an important pillar of the agricultural and forestry economy and a pioneer crop for saline-alkali land.In Xin Jiang,unreasonable irrigation systems and improper water and fertilizer management can cause soil salinization and low fertilizer utilization efficiency,leading to resource waste and environmental problems under film mulched drip irrigation.Therefore,it is necessary to improve soil quality and increase crop yield and quality as a prerequisite for the use of brackish water.After undergoing ionized treatment,the physicochemical properties of the irrigation water change,and the activity of water molecules is increased,which in turn affects the movement of soil water and salt and the crop growth.Therefore,research on improving the quality and efficiency of cotton production in arid region is essen tial to address the adverse effects of brackish water irrigation on soil and crops.This study utilized a combination of field experiments and theoretical analysis to investigate the effects of drip flow rate on wetting front migration and water salt transport un der non-ionized brackish water and ionized brackish water through drip irrigation experiments,revealing the distribution patterns of water and salt under desalinated brackish water.Furthermore,the study investigated the effects of ionized brackish water on cotton growth,physiology,nutrient absorption,yield,quality,water and nitrogen use efficiency,soil water,salt,and fertility.The study also explored the mechanisms and application effects of ionized brackish water film mulched drip irrigation on cotton quality and efficiency improvement.Additionally,comprehensive evaluation was carried out using principal component analysis,grey correlation analysis,and the Technique for Order Preference by Similarity to Ideal Solution(TOPSIS)to determine the appropriate irrigation and nitrogen application rates for cotton under non-ionized brackish water and ionized brackish water film mulched drip irrigation in arid areas.The main research results are as follows:(1)Compared with non-ionized brackish water,the ionized brackish water increased the horizontal movement distance of soil wetting front by 6.5%to 9.6%.The horizontal wetting radius increased with the increase of drip flow rate,while the maximum distance of vertical wetting front decreased with the increase of drip flow rate.The length of vertical wetting front of non-ionized brackish water was greater than that of ionized brackish water,with an increase of 10.6%to 16.8%.Ionized brackish water had an increased water storage capacity,and a higher desalination rate of 34.9%to 49.0%compared with non-ionized brackish water.The relationship between the horizontal wetting front movement distance and movement rate with time followed a power function.The change of the length of the vertical wetting front and the horizontal wetting radius conformed to the elliptical function.(2)Irrigation with ionized brackish water can significantly improve cotton plant height,leaf area index,shoot dry matter,leaf photosynthesis,relative growth rate(RGR),and unit leaf rate(ULR),as well as increase SPAD values and photosynthetic rate.As the growth period progresses,cotton plant height and shoot dry matter show an S-shape curve change,while leaf area index and leaf photosynthesis show a unimodal curve change with an initial increase followed by a decrease,and RGR and ULR exhibit exponential decline.SPAD values show a trend of first increasing and then decreasing as the growth process progresses.Plant height,leaf area index,shoot dry matter,leaf photosynthesis,RGR,and ULR all increase with increasing irrigation amount.The maximum net photosynthetic rate(Pnmax)in the light response model increase with increasing irrigation amount,and the light saturation point of cotton leaves increases with increasing irrigation amount.Plant height increase with increasing nitrogen application,and leaf area index and shoot dry matter both increase in the early growth period with increasing nitrogen application,then increase and decrease in the later growth period,reaching a maximum at a nitrogen application rate of 350 kg/ha.LAD increases with increasing nitrogen application in the early growth period,and decreases after an initial increase in the later growth period with increasing nitrogen application.NAR,SPAD values,Pnmax and the light saturation point of leaves all increase with increasing nitrogen application.Compared with non-ionized brackish water irrigation,ionized brackish water can significantly increase the nitrogen uptake of cotton plants during the bud,boll and bollopening stage,with nitrogen uptake increasing by 20.7%to 28.4%,30.6%to 42.1%,and 34.9%to 71.1%during the 3 year boll stage,respectively.(3)Under drip irrigation with ionized brackish water,the soil water storage capacity in the zone of cotton decreases,water consumption increases and soil salinity accumulation decreases.With the increase of irrigation amount,the soil water content under both non-ionized brackish water and ionized brackish water irrigation gradually increases,the soil water storage capacity increases,and the soil salinity accumulation in the 0-40 cm depth decreases.With the increase of nitrogen application,the soil water content under both non-ionized brackish water and ionized brackish water decreases gradually,and the soil salinity accumulation in the 0-40 cm depth shows a trend of increasing and then decreasing.Nitrogen application can increase the content of residual nitrate and ammonium nitrogen in the soil.We have established water production functions of cotton under non-ionized brackish water and ionized brackish water.Compared with non-ionized brackish water,ionized brackish water can increase cotton yield by 11.8%to 29.6%,and improve fiber quality index(FQI)by 13.1%to 18.1%.With the increase of irrigation amount,the yield showed a trend of first increasing and then decreasing,reaching its maximum value at 487.5 mm,while the FQI showed an increasing trend.With the increase of nitrogen application rate,the yield and FQI showed a trend of first increasing and decreasing,and the yield increased within the range of 150 kg·ha-1 to 350 kg·ha-1 of nitrogen application rate,but began to decrease after exceeding 350 kg·ha-1.Irrigation with ionized brackish water can improve the activity of soil urease,sucrase,alkaline phosphatase and catalase in root zone.The highest soil enzyme activity was observed in nitrogen application of 350 kg·ha-1.(4)Compared with non-ionized brackish water,ionized brackish water can significantly improve water use efficiency by 8.6%to 19.9%and nitrogen use efficiency by 12.5%to 29.5%.irrigation can significantly improve water use efficiency,and the highest water use efficiency was achieved with irrigation amount of 487.5 mm.Nitrogen application can significantly improve water use efficiency,agronomic nitrogen use efficiency,and apparent nitrogen recovery efficiency.Under non-ionized brackish water,the highest water use efficiency and apparent nitrogen recovery efficiency were achieved with nitrogen application rate of 350 kg·ha-1,and highest physiological nitrogen use efficiency and nitrogen partial productivity were achieved with nitrogen application rate of 150 kg·ha-1.Under ionized brackish water,the highest water use efficiency,agronomic nitrogen use efficiency,and apparent nitrogen recovery efficiency were achieved with nitrogen application rate of 300 kg·ha-1,while the highest physiological nitrogen use efficiency and nitrogen partial productivity were achieved with nitrogen application rate of 150 kg·ha-1.(5)Critical nitrogen dilution models for cotton under non-ionized brackish water and ionized brackish water were established.The analysis results of the three evaluation methods all indicate that the nitrogen application rate of 3 50 kg·ha-1 under ionized brackish water is the best for cotton.Therefore,the suitable irrigation amount and nitrogen application rate for cotton in the arid region of Northwest China under ionized brackish water are 487.5 mm and 350 kg·ha-1,respectively.