Factors controlling potentially mineralizable and recalcitrant soil organic matter in humid Asia

Kadono, Atsunobu; Funakawa, Shinya*; Kosaki, Takashi*

To understand the dynamics of soil organic matter (SOM) in humid Asia, several properties were tested to estimate the amounts of potentially mineralizable carbon (PMC) and nitrogen (PMN) as well as recalcitrant carbon (ROC) and nitrogen (RON). Eighty-nine surface soil samples were collected in Thailand, Indonesia and Japan from cropland and forest ecosystems. The fresh soils were incubated under constant conditions, and the CO and the mineral N from the soils were monitored. PMC and PMN were determined by fitting models to the cumulative curves of the emitted C and N. ROC and RON were determined by the subtraction of PMC and PMN from TC and TN, respectively. Using multiple regression analysis with the stepwise method, PMC and PMN was well estimated by carbon and nitrogen content of light fraction (LFC and LFN) and clay content, while ROC and RON were estimated by LF-OM, amorphous materials and clay content, suggesting the importance of parent materials in this region.