This study was designed to explore changes in soil bulk density, soil organic carbon content, soil organic carbon stock and soil labile organic carbon fractions under 34 years fertilizer regime in the double-cropping rice system of southern China. The experiment including five fertilizer treatments: chemical fertilizer alone (MF), rice straw residue and chemical fertilizer (RF), 30% organic manure and 70% chemical fertilizer (LOM), 60% organic manure and 40% chemical fertilizer (HOM), and without fertilizer input as control (CK). The results showed that soil bulk density in the 0-20 cm soil layer with long-term fertilizer treatments were significantly decreased compared to CK treatment. The soil organic carbon content and stock with RF, LOM and HOM treatments were significantly higher than that of MF and CK treatments. These results confirmed by the soil carbon management index which were significantly increased with RF, LOM and HOM treatments. As a result, combined application of organic manure with chemical fertilizer is a benefit nutrient management for improving soil organic carbon content and stock, soil carbon management index in paddy field of southern China.

本研究旨在探讨在华南双季稻制度下34年施肥条件下土壤容重，土壤有机碳含量，土壤有机碳储量和土壤不稳定有机碳组分的变化。该实验包括五种肥料处理方法：单独的化肥（MF），稻草残渣和化肥（RF），30％的有机肥料和70％的化学肥料（LOM），60％的有机肥料和40％的化学肥料（HOM），且没有肥料输入作为对照（CK）。结果表明，与CK处理相比，长期施肥后0-20 cm土层的土壤容重显着降低。RF，LOM和HOM处理的土壤有机碳含量和储量显着高于MF和CK处理。这些结果已通过土壤碳管理指数得到了证实，而RF，LOM和HOM处理则显着提高了土壤碳管理指数。因此，有机肥与化肥的联合施用是改善我国南方稻田土壤有机碳含量和储量，土壤碳管理指标的有益养分管理。