Research On Coupling Effect Of Water And Nitrogen On The Cotton Growth Of Under-film Dripping Irrigation Under Ionized Brackish Water

Xinjiang is located in the northwest arid area of China with plenty of brackish water resources and saline-alkali soil resources.High-efficient utilization of brackish water is an effective way to address water resources shortage in drought areas aind develop water saving irrigation.Field experiments were conducted on the soil water-salt distribution,nitrogen transport and cotton growth by using ionized brackish water of under-film dripping irrigation.There were 20 treatments,included irrigation rate from 175 to 375 m3/mu,non-activated brackish water control;nitrogen application rate from 150 to 450 kg/hm2,control.The main research results are as follows:(1)The ionized brackish,water irrigation treatment could enhance the water holding capacity of soil effectively,then promote the absorption of cotton roots to water.The soil moisture and water consumption content in cotton root zone of ionized brackish water treatment were greater than the non-activated brackish water control.The ionized brackish water irrigation treatment could improve the water desalting ability and decrease the salt salinty of root zone effectively,the soil salt content in the main root area of ionized brackish water was less than brackish water control.The ionized brackish water irrigation treatment could reduce soil re sidual nitrogen in the root zone,the the contents of nitrate-N and ammonium-N of ionized brackish water treatment were less than control treatment,which is conducive to the growth of cotton roots.(2)Both water and nitrogen fertilizer applied had remarkable impact on cotton growth characteristics,the cottoln plant height,stem diameter and leaf area index were increased by increase of irrigation water and nitrogen fertilizer.Enlarging the amount of irrigation and nitrogen fertilizer properly could enhance the photosynthesis rate of cotton leaves,the maximum net photosynthetic rate of irrigation treatments in order are W375(high),W325,W275,W225,W175;the maximum net photosynthetic rate of nitrogen fertilizer treatment.s in order are N350(high),N300,N450,N250,N150.The ionized brackish water irrigation treatment could promote the growth and development of cotton,the plant height,stem diameter,leaf area index,chlorophyll content and net photosynthetic rate of cotton of ionized brackish water treatment were larger than control treatment.(3)The cotton biomass,yield and water-nitrogen use cefficiency increased remarkably in appropriate dosage of water irrigation and nitrogen fertilizer,in wrhich the W325 treatment and N350 treatment are the most effective.Using the water production function to derive the optimal solutions of water and fertilizer amount and the optimum of cotton yield.Compared with the non-activated brackish water,the ionized brackish water irrigation has an extensive effect on increasing the yield and water using efficiency,which make the total biomass of cotton increased by 6.2%?12.4%,and cotton yield increased by 5.6%?12%·(4)The cotton growth model developed based on the construction of logistic model,and has involved both water irrigation and nitrogen fertilizer.The accuracy test result indicated that the growth model could well describe the processes of cotton plant height,leaf area index and biomass change with the growth time.