Effects of Combined Application of Chemical and Organic Fertilizers on Soil Salinity and Corn Water and Fertilizer Utilization in Hetao Irrigation District

In order to find out the effect of combined application of chemical fertilizers and organic fertilizers (respectively replacing 0, 25%, 50%, 75% and 100% of chemical fertilizer nitrogen with organic fertilizer nitrogen) on the migration of salt and the utilization of water and fertilizer for corn in the plough layer (0~40cm) of Hetao Irrigation Area, a three-year field positioning fertilization experiment was carried out in the typical moderately saline-alkali land of Hetao Irrigation Area from 2017 to 2020, aiming to provide a theoretical basis for formulating environmentally friendly fertilization measures for the sustainable development of saline irrigation area.The results showed that the continuous application of chemical and organic fertilizers for three years significantly promoted the desalination of the plough layer, inhibited the return of soil salt, and significantly reduced the SO₄^2- content in the soil.With the increase of the replacement ratio of organic fertilizer, the content of Na⁺ and Cl^- gradually increased, the content of SO₄^2- gradually decreased, and the effect of salt control continued to improve;With the advancement of the growth period, the effect of salt control continued to decline.The higher the proportion of organic fertilizer application, the better the stable yield, while the corn yield and water and fertilizer utilization capacity showed a parabolic law of "first increase and then decrease" with the increase of the organic fertilizer replacement ratio.Comprehensive consideration, 25% of the organic fertilizer replacement rate is the best, and the combination of three years can reduce 4.73% of the soil salinity in the plough layer, increase the yield by 15.38%, improve the water use efficiency by 14.03%, and increase the partial productivity of fertilizers by 15.52%;The replacement rate of 50% organic fertilizer is second, and the combined application of three years can reduce the soil salinity of the plough layer by 6.31%, increase the yield by 11.71%, improve the water use efficiency by 9.35%, and improve the partial productivity of fertilizer by 11.64%.The excessively high organic fertilizer application ratio (≥ 75%) can further improve the soil salt control effect and yield stability, but it will significantly reduce the yield of corn, and it is not conducive to the utilization of water and fertilizer by corn.