Abstract:

【Objective】 The effects of 25-year application of fertilizer and combining fertilizer with rice straw on water-stable aggregates size distribution and content and storage of aggregate-associated organic carbon and nitrogen were studied. 【Method】 The experiment was established in 1981 on a Typic Hapli-Stagnic Anthrosols. The treatments selected in this study were: CK: (without fertilization), NP(N,P fertilizers), NPK(N,P,K fertilizers), NP+RS(NP plus rice straw) and NPK+RS (NPK plus rice straw). 【Result】 Results showed that long-term application combining fertilizer with rice straw increased the content of water-stable aggregates in the 2-5 mm and 0.5-2 mm size fraction. Long-term application combining fertilizer with rice straw significantly increased the contents of organic carbon (OC), total nitrogen (TN) and potential mineralizable N (PMN) , and also increased the storages of OC, TN and PMN in these water-stable aggregates (2-5 mm, 0.5-2 mm). It was found in this study that balanced fertilization treatment with N, P and K fertilizers could increase the contents and storages of OC, TN and PMN in the water-stable macroaggregates (2-5 mm, 0.5-2 mm) compared with CK treatment, but the range of increase of OC, TN and PMN was lower in NPK treatment than in the treatments with combined application of fertilizer with the rice straw. Water-stable aggregate protected organic carbon and nitrogen were significantly greater for macroaggregates (2-5 mm and 0.5-2 mm) than for microaggregates (＜0.25 mm), indicating physical protection of organic carbon and nitrogen within macroaggregates. 【Conclusion】 Long-term application of fertilizer combined with rice straw increased significantly the contents and storages of OC, TN and PMN in water-stable macroaggregates(2-5 mm, 0.5-2 mm), which is an effective measure to improve soil structure, increase soil fertility in red paddy soil.

Key words: long-term fertilization')">long-term fertilization, red paddy soil, water-stable aggregate, organic carbon (OC), total nitrogen (TN), potentially mineralizable nitrogen (PMN)