Net mineralization of the native SOM can be an important mechanism of acid neutralization in cropland soils, as organic
anions in soil consume protons in mineralization process (Poss et al., 1995). However, acid neutralization by this process can be hypothesized to be low in SOM-poor sandy soils (Lesturgez et al.,2006). In addition, the low water-holding capacity of sandy soil may cause a rapid leaching of nitrate and cations from the rooting zone (Nyamangara et al., 2003). The uniqueness of tropical sandy soils may have strong influences on proton-generating and-consuming processes (Fujii et al., 2013).