Abstract: 【Objective】Studies on changes in organic carbon and nutrient contents of the highly productive paddy soils would be scientifically beneficial to the directional management and sustainable utilization of paddy soils. 【Method】The contents of organic carbon and nutrients and their changes in the last over 20 years in the highly productive paddy soils as related to the environmental significance were investigated by field sampling and comparison with the corresponding values in the Second Soil Survey in Yujiang County of Jinagxi Province. 【Result】Results showed that 0-10 cm depth highly productive paddy soils in Yujiang County of Jiangxi Province contained organic carbon content of (20.2±3.88) g·kg-1, total N (2.09±0.55) g·kg-1, available phosphorus (42.7±32.7) mg·kg-1, respectively, all were at the very rich level. In the last over 20 years, the organic carbon pool of the highly productive paddy soils remained a stable state, total N and available P increased significantly, while available K changed little. The amount and percentage of P immobilized in 0-10 cm highly productive paddy soils were (142.7±41.1) mg·kg-1 and (36.2±10.4)% and of added P CEC was (7.93±1.32) cmol·kg-1, being not higher than the mean value of paddy soils and that in upland red soils. It indicated that fertilizer P in highly productive paddy soils would be a high mobility and easily moved to water, being a main source of nutrient causing eutrophication. 【Conclusion】For a long-term rice cultivation and fertilization, the highly productive paddy soils were very rich levels of organic matter and available P, and a steady state of organic carbon pool, while amount of P immobilized was not high. Because of a weak K-fixing capacity, the available K content was not rich in highly productive paddy soils, suggesting that attention should be paid to the balance and increase of soil K pool.

Key words: Yujiang County of Jiangxi Province, Highly productive paddy soils, Organic carbon, Nutrients