Spatiotemporal Variation in Soil Available Potassium in Central and Western China

The status in soil Available Potassium (AK) and their spatiotemporal changes are essential for nutrient management and food security. However, research on the regional-scale variations in AK remains limited. Based on the data from 3,318 sites in the 1980s and 2010s, combined with a variety of machine learning methods, this study systematically assessed the spatial distribution and stock changes of available potassium density (AKD) in central and western China. The results show that the random forest model demonstrated strong predictive performance for both periods (RMSE : 0.55–0.59 g·m ² , R²: 0.36–0.43). From the 1980s to the 2010s, the total AK stock in central and western China decreased by 12.65%. Natural ecosystems experienced a 16.01% reduction in stock due to ecological degradation and overgrazing, while agroecosystems saw a 12.71% increase in stock through enhanced potassium fertilizer application and improved soil management practices such as straw returning. Spatially, AKD was higher in the western regions and lower in the central regions. The available potassium stock on the Tibetan Plateau declined, whereas significant accumulation was observed in areas such as the Chengdu Plain and the Loess Plateau. Analysis of driving factors indicates that topography and climate were the dominant factors, with land use and vegetation playing important regulatory roles. The study underscores the necessity of high-resolution assessments of potassium dynamics, providing a scientific basis for precise nutrient management, arable land quality improvement, and regional agriculture and ecological restoration.