Abstract:

【Objective】 To investigate the effects of rice straw incorporation in situ and ex situ on soil organic carbon and active organic carbon in red soil hilly region. 【Method】 This study was conducted on slope upland and upland-paddy rotation in a long-term field experiment in red soil hilly region for 6 years, and three treatments were established, including CK (no fertilizer), NPK and straw + NP (S+NP). 【Result】 Soil organic carbon (SOC) in slope upland significantly increased by 14.6% and 36.2% in NPK and S +NP treatments compared to the initial value, respectively. Microbial biomass carbon (MBC) remained an increasing trend on the whole, and it significantly increased by 16.1% and 33.5% in NPK and S+NP treatments compared with CK. Dissolved organic carbon (DOC) was increasing yearly, and there was no significant difference among 3 treatments. SOC in paddy-upland rotation was almost steady in 6 years, but was lower than initial value in NPK and CK treatments. MBC remained the same trend as that in slope upland, and significantly increased by 14.2% in S+NP compared with CK, but declined in NPK. DOC had a decline trend in the late 2 years, and it was lower in NPK and S+NP treatments than that in CK. 【Conclusion】 Rice straw incorporation in situ and ex situ increased SOC and MBC compared with single application of chemical fertilizer, and the effect was more significant for straw incorporation ex situ in only few years. DOC had little response to fertilizer treatments, and the content was higher in slope upland with only 6 years cultivation than in paddy-upland rotation land with long-term cultivation.

Key words: straw incorporation in situ, straw incorporation ex situ, soil organic C, soil active organic C