Mechanisms controlling the stabilization of soil organic matter in agricultural soils as amended with contrasting organic amendments: Insights based on physical fractionation coupled with 13C NMR spectroscopy
Kiattisak Sonsri, Haruka Naruse, Akira Watanabe
Abstract
C nuclear magnetic resonance (NMR) along with OAs and bulk soil samples. The long-term OA applications enhanced the total C accumulation and the amount of C accumulated as oSOM, wSOM, and sSOM correlated positively with the total C content. The application of BC or CRC resulted in a greater accumulation of fSOM. Conversely, the continuous application of SSC or CMC, which has a high N content and a low C/N ratio, led to a greater accumulation of C, mainly as wSOM. Our findings suggest that both the quality and quantity of OAs control the forms of C that accumulate and this involves different mechanistic pathways. We suggest that the abundant alkyl C in the wSOM and sSOM fractions was SSC-derived SOM in the SSC soil while in the case of the CMC soil, this was due to the increased contribution of microbial-derived SOM.