Effects of long-term cycling of organic matter on soil phosphorus supplying capacity in a red soil paddy ecosystem

The soil P supplying capacity in red paddy soils of different long-term fertilization systems (1990-2004) was investigated using pot experiment, and the differences of soil P supplying capacity in different fertilization treatments were also studied according to the change of soil P balance, total P, organic P, Olsen-P and MB-P. The results indicated that soil P supplying capacity was significantly increased by long-term chemical P fertilizer application and kept at the highest level in the chemical P fertilizer application combined with long-term cycling of organic matter, at the same time, the average P uptake of plantation in this treatment was 3.5 times than control (no chemical P fertilizer application), and 59.8% higher than chemical P fertilizer application (NP, NPK). In the long-term chemical N fertilizer application treatment, soil P supplying capacity was very low and the total P uptake of plantation was decreased by 17.2% compared with no fertilizer application. In the application of organic matter cycling and organic matter combined with N fertilizer treatments, the total P uptake of plantation were increased by 80.3% and 40.2%, respectively. Long-term organic matter cycling obviously improved microbial fixation of soil P, and it was the key approach for the conversion of inorganic P into extractable P accomplished by microorganisms in paddy soils. Therefore, cycling of organic matter combined with chemical P fertilizer was a good fertilizer management strategy to improve soil P supplying capacity.