Abstract:In order to explore the spatial-temporal distribution characteristics and variation rules of soil salt content caused by the reduction of channel lining and drainage water after water-saving transformation in Shenwu irrigated district, fixed-point monitoring of regional soil information was adopted, combined with classical statistics, spatial interpolation and machine learning modeling and inversion, and spectral data was obtained by Landsat 8 satellite. By processing the measured soil salt content, spectral index and band reflectance, using Adaboost regression, BP neural network regression, gradient lifting tree regression, KNN regression, decision tree regression and random forest regression, the spatial inversion model of soil salt content in Shenwu irrigated district was constructed. The optimal inversion model was used to invert the spatial distribution characteristics of soil salt content in Shenwu irrigated district. The results showed that the correlation coefficient was screened by the whole variable single regression method. With nine spectral factors of 0.55, six inversion models of machine learning were constructed using SPSS PRO software, and the accuracy of the six inversion models was compared. The verification set R2 from high to low was random forest regression, gradient lifting tree regression, Adaboost regression, KNN regression, decision tree regression, and BP neural network regression. The random forest regression model had the best fitting accuracy, and the R2 of training set and verification set were 0.834 and 0.86, respectively. It was showed that random forest regression model had better inversion effect. The inversion results showed that the non-salinization soil increased by 391.7km2, accounting for 21% of the total irrigation area, while the moderate salinization soil, severe salinization soil and saline soid reduced the square by 95.61km2, 63.37 km2 and 45.7 km2, accounting for 5%, 3% and 2% of the total irrigation area, respectively. In summary, after the completion of the water-saving transformation project, the degree of soil salinization in Shenwu irrigated district was reduced, and the area of crop growth security area was increased. However, due to the reduction of channel lining and drainage water, the effect of soil salt leaching was weakened, and soil salt migrated within the irrigation area, the overall soil environment was improved, and salt accumulation occurred in some areas.
