Evaluation of the Potential of Using Machine Learning and the Savitzky-Golay Filter to Estimate the Daily Soil Temperature in Gully Regions of the Chinese Loess Plateau

Soil temperature directly affects the germination of seeds and the growth of crops. In order to accurately predict soil temperature, this study used RF and MLP to simulate shallow soil temperature, and then the shallow soil temperature with the best simulation effect will be used to predict the deep soil temperature. The models were forced by combinations of environmental factors, including daily air temperature (Tair), water vapor pressure (Pw), net radiation (Rn), and soil moisture (VWC), which were observed in the Hejiashan watershed on the Loess Plateau in China. The results showed that the accuracy of the model for predicting deep soil temperature proposed in this paper is higher than that of directly using environmental factors to predict deep soil temperature. In testing data, the range of MAE was 1.158-1.610 degrees C, the range of RMSE was 1.449-2.088 degrees C, the range of R2 was 0.665-0.928, and the range of KGE was 0.708-0.885 at different depths. The study not only provides a critical reference for predicting soil temperature but also helps people to better carry out agricultural production activities.