Effect On Water-Nitrate Utilization Characteristics Under Residue Plastic Film And Irrigation And Its Physiological Mechanism Research In Cotton Field

Plastic film mulching technology is a safeguard measure for water saving agriculture in Xinjiang.In recent years,with the use of high strength of plastic film and the lack of effective recycling measures,the"white pollution"is widespread.The residual film changed the water and fertilizer environment of soil and the water absorption of the root system,Leading to decline in the quality of the cultivated land,and deterioration of crop growth environment,the water use efficiency and production potential of crops were decreased seriously.In this study,field experiments were conducted to investigate the effect of residual film accumulation on the movement and distribution of water and nitrogen in cotton fields,the evapotranspiration of crops and the transformation of water consumption structure,and how to respond to irrigation regulation measures of cotton main producing areas under drip irrigation conditions for 2consecutive years.The experimental design was a 3×3 factorial with three residual plastic film amount(0,225 and 450 kg·hm^-2,denoted as T1,T2 and T3,respectively)and three irrigation levels(reducing irrigation 3450 m³·hm^-2,conventional irrigation 4650 m³·hm^-2 and incremental irrigation 5850 m³·hm^-2,denoted as W1,W2 and W3,respectively).Among them,the residual film for the main benefits,irrigation for the side effects.Research on the effects of different irrigation and residual film treatments on water dissipation structure,water and nitrogen transport and distribution,nutrient uptake and utilization,water use efficiency and yield components.The results of this study provide a theoretical basis for the quantitative description of the process and links of the residual damage of plastic film and the scientific development of the prevention and control of the film pollution and the rational use of film mulching cultivation technology.The main results as follows:1.The soil water use efficiency and WUE decreased gradually,with the increment of residual film.The total evapotranspiration was not significantly different during the whole growth period among the different treatments.Under reduced irrigation（W1）,The E and E/ETc partition coefficient decreased gradually with the increase of the amount of residual film;Under conventional irrigation（W2）,Then the opposite trend,450 kg·hm^-2 treatment was higher than the less residual film treatment of 12.4%and 17.7%,respectively.Incremental irrigation（W3）,The change of E and E/ETc was smaller in the residual film treatments.With the increase of irrigation amount,The E/ETc partition coefficient was reduced significantly,but ETc of cotton field is obviously increased,which is not conducive to the improvement of WUE.2.Soil water retention capacity was decreased,and hinders the migration of soil moisture in the vertical and horizontal directions due to residual film,leaving the water in the upper soil;With the increase of the amount of residual film,the migration of soil moisture in the horizontal direction is faster than the vertical direction,and the more the residual film is,the greater the unevenness.With the increase of days after irrigation,the soil moisture content decreases rapidly when the amount of residual film increases.Increased irrigation,soil moisture and soil wet areas increased significantly,and the wetting front moves downwards,And the uneven distribution of water caused by residual film gradually decreased.3.The effect of nitrate nitrogen transport along the horizontal and vertical directions was significantly enhanced with the increase of the amount of residual film,The more the residual film is,the greater the unevenness within the sampling site.Horizontal edge,no residual film treatment of nitrate nitrogen content is the highest,While the vertical direction is just the opposite,with redistribution of water after irrigation.There was a serious leaching phenomenon occurred in the vertical direction,along the horizontal direction of the cumulative accumulation,and the uneven distribution of nitrate distribution decreased due to residual film.In addition,The residual nitrogen content in 10²0 cm or 20³0 cm soil layer increased with the increase of the amount of residual film,With the increase of irrigation,the trend of inorganic nitrogen was the first increase and then decrease,and moved to deep layer,which could cause environmental risk.4.Residual film inhibited the growth of cotton,is not conducive to nutrient absorption,With the increase of the amount of residual film,LAI,biomass and seed cotton yield decreased significantly.Appropriate increase amount of irrigation（W1 to W2）,and the biomass,nutrient absorption and yield of cotton increased obviously,At the same time,the water consumption of cotton field also increased significantly by 21.0%.Although increased the amount of irrigation can slow down the negative effect of the residual film pollution,but will increase the water consumption of cotton field,significantly.