Particulate organic matter (POM), as an active pool of soil organic carbon, play an important role in C sequestration in cultivated soil.Formation of POM is related to aggregate format ion and sensitive to land use and soil management.The objectives of this study are (1) to determine effects of fertilization on POM content in paddy soil;(2) to determine effect of fertilization on formation and stability of aggregates;and (3) to clarify relationship between POM and aggregate stability.Soil samples were collected from the experiment fields of the long-term fertilization experiment station treated separately with CK (without fertilization), NPK (chemical N, P, K fert ilizers), NPK(=) (double the dose in Treatment NPK) and NPK + OM (NPK plus farmyard organic manure).The results showed that fertilization increased significantly the content of POM in the soil.In Treatments NPK, NPK(=) and NPK+ OM, it increased by 1.1~1.3, 1.2~1.4 and 1.5~1.9 t imes over that in CK and in Treatment NPK+ OM it was 37%~71% higher than that in Treatments NPK and NPK(=).The C/N ratio decreased with the increase in aggregate size, suggesting that the POM in smaller aggregates was older than in larger ones.In terms of aggregate stability, the treatments were in a decreasing order of NPK+ OM> NPK(=) > NPK> CK.The aggregate stability had a very significant linear correlation with POM (r = 0.98, p < 0.01).These results suggest that fertilization increased POM level due to increased input of organic materials into soil, thus enhancing soil aggregation.