Abstract: 【Objective】 For revealing the mechanism of soil P fertility changes, the influences of different patterns of long-term fertilizer application for 16 years on phosphorus adsorption-desorption characteristics at the layers of 0-20 cm and 20-40 cm were studied in a reddish paddy rice field. 【Method】 Soil samples collected from the long-term experimental field were incubated in a constant temperature cabinet and parameters of soil P adsorption, rate of soil P desorption and amount of accumulative P desorption were then determined. 【Result】 The characteristics of soil P adsorption-desorption were changed remarkably under different patterns of long term fertilizer application, especially at 0-20 cm of soil layer. The affinity constant (k) of soil P adsorption, the maximal P adsorption (Q) and the buffering capacity of P adsorption (MBC) were declined significantly at the layer of 0-20 cm by the employment of long term organic nutrient recycling, and meanwhile, the amount and rate of accumulative soil P desorption were increased significantly in this soil layer. Organic nutrient recycling combined with chemical fertilizer application was more effect in declining soil P adsorption parameters and increasing the amount and rate of accumulative P desorption at 0-20 cm compared with that of organic nutrient recycling alone. There was no significant difference between treatments of NPK fertilizer application and the control without tertilize application on soil phosphorus adsorption-desorption characteristics. 【Conclusion】 Combination of NPK fertilizer and organic nutrient recycling could significantly decrease soil phosphorus adsorption and enhance P desorption of the plough layer, and hence increase soil P fertility in the reddish paddy rice field. The effects of organic nutrient recycling on soil P adsorption-desorption would not increase the risk of P pollution of water environment.

Key words: long-term experiment, organic nutrient recycling, reddish paddy soil, phosphorous adsorption and desorption