The driving factors and buffering mechanism regulating cropland soil acidification across the Sichuan Basin of China

•Cropland soil pH declined by 0.30 units during 1980s–2010s.•Soil pH decline mainly occurred in areas with initial pH < 7.5.•Precipitation acted more importantly in driving pH decline than fertilization and crop production.•Soil pH decline was primarily buffered by soil carbonate and secondarily by CEC.•5. Carbonates provides buffering capacity when it exceeds 36.76 g kg−1, otherwise soil CEC.