Effect Of Magnetized Water Irrigation Mode On Soil Water And Salt Distribution And Cotton Growth

Optimizing the magnetized water irrigation mode and constructing a cotton growth model are of great significance to the rational use of limited water resources in arid areas and ensuring the sustainable development of agriculture.The effects of irrigation before sowing with magnetized water and unmagnetized water and rotational irrigation on soil water and salt distribution and cotton growth characteristics were studied by plot and field experiments.Established a universal cotton growth model by the statistical analysis of cotton growth data.The relationship between the maximum leaf area index of cotton and irrigation amount,nitrogen application rate,planting density and yield during the whole growth period was analyzed,which provided scientific basis for efficient and reasonable field managcement.The main research results are as follows.(1)The flooding irrigation of magnetized brackish water before sowing can improve the water storage capacity of soil.The average water content of magnetized brackish water after 3 days and 40 days of irrigation is greater than that of brackish water.Magnetizing fresh water and brackish water before planting can reduce soil salt accumulation.In the soil layer within 40 cm,compared with fresh water,the salt rejection of magnetized fresh water 3 days after irrigation has increased by 8.1%.In the soil layer within 40 cm,compared with brackish water,the salt recjection of magnetized brackish water 3 days after irrigation has increased by 8.2%,In the soil within 40 cm,compared with unmagnetized water,the salt rejection of magnetized fresh water and magnetized brackish water after 40 days of irrigation increased by 9.1%and 6.1%,respectively.Magnetization of brackish water or fresh water before sowing improved cotton emergence rate and promoted cotton seedling growth.Compared with brackish water,the germination rate of magnetized brackish water cotton increased by 15.1%.The flooding irrigation of magnetized brackish water or fresh water before sowing improved the growth of cotton vegetative organs,enhanced the utilization efficiency of cotton for strong light,increased the chlorophyll content,promoted the photosynthesis of leaves to a certain extent,and improved the utilization efficiency of cotton for light energy.(2)Compared with fresh water irrigation during the whole growth period of cotton,the total water consumption of cotton increased by about 4.3%under magnetized fresh water irrigation only during vegetative growth stage.At the same time,the field desalination rate per hectare increased by 8.2%,and the yield and water use efficiency increased by 8.3%and 3.6%,respectively.Magnetized fresh water irrigation only during vegetative growth stage is conducive to the utilization of strong light by cotton,slowing down the consumption rate of oxygen and organic matter,and conducive to the accumulation of dry matter in crop reproductive organs and high yield of cotton.(3)Compared with brackish water irrigation during the whole growth period of cotton,the total water consumption of magnetized brackish water irrigation during the whole growth period increased by about 4.1%,and the increased water consumption was mainly concentrated in the seedling stage and bud stage.Meanwhile,cotton yield and water use efficiency increased by 15.4%and 10.8%,respectively.Magnetized brackish water irrigation during the whole growth period can create the basis for the accumulation of dry matter in cotton reproductive organs,so that the ability of cotton to use strong light and weak light has been enhanced,while reducing the rate of oxygen and organic matter consumption during dark respiration,significantly improving cotton yield and water use efficiency.(4)Through the comprehensive analysis of magnetized and unmagnetized fresh water and brackish water irrigation treatment,the average water content of fresh water and magnetized fresh water irrigation treatment is relatively high in each growth period,and the water consumption of magnetized and unmagnetized brackish water irrigation treatment is relatively high in the whole growth period.Meanwhile,the yield and water use efficiency of fresh water irrigationand magnetized fresh water irrigation were significantly higher than those of brackish water irrigation and magnetized brackish water irrigation.In addition,the yield and water use efficiency of magnetized fresh water irrigation at vegetative growth stage and fresh water irrigation at reproductive growth stage were the highest,and the yield and water use efficiency of magnetized brackish water irrigation at whole growth stage were close to that of fresh water irrigation.(5)Logistic model and modified Logistic model can well simulate the change trend of cotton growth index with GDD under mulched surface irrigation,drip irrigation of magnetized water and unmagnetized water with film mulching.The plant height and dry matter accumulation of drip irrigation cotton under drip irrigation of magnetized water and unmagnetized water with film mulching showed the growth characteristics of ’fast in the middle stage and slow in the early and late stages ’.The leaf area index of cottonunder mulched surface irrigation,drip irrigation of magnetized water and unmagnetized water with film mulching showed a trend of increasing first and then decreasing.The GDD was 1495℃ when the leaf index under drip irrigation of magnetized water with film mulching was the largest.The GDD was 1450℃ when the leaf index under drip irrigation of unmagnetized water with film mulching was the largest.The GDD was 1627℃ when the leaf index under surface irrigation without mulching was the largest.RGDD can uniformly analyze the relative leaf area index of cotton under different varieties and field management measures to reflect the overall characteristics of cotton growth in China.Comprehensive consideration of the effects of irrigation amount,nitrogen application rate and planting density can accurately describe the variation characteristics of maximum leaf area index and yield.When the maximum leaf area index was 4.93,the yield of seed cotton reached 6066.2kg·hm-2.For areas with extreme water shortage,irrigation before sowing with magnetized brackish water can provide a relatively good environment for the early growth of crops.When fresh water is irrigated in the field,the use of magnetized fresh water irrigation in the vegetative growth stage is conducive to soil water retention,salt washing and yield increase;When irrigated with brackish water in the field,using magnetized brackish water irrigation during the whole growth period can enhance the photosynthesis and growth indexes of cotton,and significantly improve the yield and water use efficiency of cotton.