Digital mapping of soil texture components in part of Khuzestan plain lands using machine learning models

Document Type : Research Paper

Authors

1 Department of Soil Science and Engineering, Faculty of Agriculture, Shahid Chamran University of Ahvaz, Khuzestan, Iran

2 Professor at Department of Soil Science, Faculy of Agriculture, Shahid Chamran University of Ahvaz, Khuzestan, Iran

3 Associate Professor, Department of Soil Science, College of Agriculture, Shahid Chamran University of Ahvaz

10.22059/ijswr.2022.348442.669360

Abstract

This study aims to evaluate and to compare the efficiency of support vector machine (SVM) and random forest (RF) models using digital soil mapping approach to predict soil texture in part of Khuzestan province. In February 2019, before to determine soil texture in the laboratory, soil samples were taken using stratified random sampling from the surface layer )0-10 cm(. Auxiliary variables included primary and secondary derivatives of digital elevation model (DEM), remote sensing spectral indices (RS), from which the appropriate category was selected using principal component analysis (PCA). Based on PCA method, nine topographic variables from DEM and eight vegetation indices and spectra from RS were selected to predict soils texture components (sand, silt, and clay). The efficiency of the models was evaluated using the coefficient of determination (R2) and the root mean squared of the error (RMSE). The results indicated that the random forest model had higher accuracy and less error than the support vector machine model (SVM), so that values of R2 in this model were 0.80 for sand, 0.81 for silt, and 0.78 for clay, and the RMSE in the prediction of these particles were 6.02, 5.89 and 6.02, respectively, while the R2 and RMSE in the support vector machine model for prediction of sand, silt and clay were ( 0.39, 13.70), ( 0.45, 10.70), and (0.46, 9.32), respectively. Also, the results of this evaluation showed that salinity index, brightness index, and channel network were the most important environmental variables predicting clay, silt, and sand particles, respectively, and then the 6-band Landsat 8 satellite or the far infrared band was the most important variable in estimating the amount of soil texture components. In conclusion, we suggest using Random Forest model as a useful and reliable method in preparing digital maps of soil texture in the study area.

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