Effects of different farming patterns on soil organic carbon distribution and oxidation stability in purple paddy soil

Effects of different farming patterns on soil organic carbon distribution in profile and oxidation stability in purple paddy soil of long term experiment site (since 1990) were studied. Results showed that the content of soil organic carbon (SOC) decreased gradually with the increase in depth among different kind of treatments. The SOC content, reaching 20.69 g kg^-1, in 0-10 cm soil layer with the treatment of NRR(no-tillage and ridge, rice and reap) was the highest, while with the treatment of RRR(Rotation of waterloging rice and dry reap) the content was the lowest being only around 14.93 g kg^-1. The organic carbon density in 0-20 cm and 0-60 cm soil layer with the treatment of NRR were obviously higher than that with CRWF(Conventional tillage, rice and winter fallow) and RRR. It indicated that carrying out long-term NRR may lead to the enrichment of SOC in macroaggregates of the surface soil layer. The readily oxidizable organic carbon (ROOC) content with the treatments of CRWF and NRR decreased gradually along with increasing soil depth. The general trend of RRR showed a slight increase at first and then gradually went down. The content of ROOC of CRWF was evidently higher than those of NRR and RRR in 0-10 cm and 10-20 cm soil layer and the oxidation stability coefficient(Kos) of CRWF was lower than those of NRR, suggesting that the treatment of NRR had positive effect on the stability of soil organic carbon in the cultivable layer. In conclusion, farming patterns have a greater impact on the soil organic carbon accumulation and transformation.