In this study, we quantified proton budgets in the sandy soils under sugarcane and mango plantation to analyze the dominant soil-acidifying and buffering mechanisms under different vegeta-tion covers within a cropland system. We answered three questions: (1) whether the magnitude of nitrate leaching is large throughout the wet season in the sandy soils, (2) whether the dominant soil-acidifying processes differ between a sugarcane field and a mango plantation, and (3) whether proton consumption from the net mineralization of SOM is sufficiently high to neutralize acidity in the sandy soil.