稻草还田和易地还土对红壤丘陵农田土壤有机碳及其活性组分的影响

 【目的】探讨稻草还田和易地还土对红壤丘陵水田和旱地土壤有机碳及活性有机碳的影响。【方法】以红壤丘陵区长期定位点坡旱地和水旱轮作地为研究对象，选取3个处理：不施肥（CK）、单施化肥（NPK）和稻草配施氮磷肥（S+NP），对试验6年来的数据进行分析。【结果】与初始值相比，坡旱地NPK和S+NP处理在前4年内土壤有机碳（SOC）明显增加，平均增幅分别为14.6%和36.2%，此后波动较小;微生物量碳（MBC）总体保持增加趋势，NPK和S+NP处理显著高于CK，平均增幅分别为16.1%和33.5%;溶解有机碳（DOC）保持逐年增加，处理间差异不显著。水旱轮作地各处理土壤有机碳6年内基本保持稳定，但NPK和CK处理均低于初始值;MBC总体亦具有增加趋势，S+NP处理明显高于CK，平均增幅为 14.2%，但NPK处理低于CK;DOC后期出现降低趋势，且NPK和S+NP处理均低于CK。【结论】与单施化肥相比，稻草还田和易地还土均能明显提高土壤SOC和MBC含量，但稻草易地还土的效果更为显著，并在短期内表现明显。土壤溶解有机碳对施肥的响应较差，耕作时间较短的坡旱地土壤溶解有机碳含量明显高于耕作时间较长的水旱轮作地。

Effects of Rice Straw Incorporation in situ and ex situ on Soil Organic C and Active Organic C in Agricultural Soils in Red Soil Hilly Region

【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.