Study on the Phosphate Buffering Capacity and Fertiphos Requirement of Red Soils under Chinese Fir Stand

The phosphate buffering capacity and fertiphos requirement of red soils under Chinese fir ( Cunninghamia Lanceolata) stand in Fujian province are studied. The results obtained by the experiments of isothermal phosphate adsorption show that the red soil can adsorb large amount of phosphorus.Phosphorus could be adsorbed firmly by the soil,so it will decrease the availability.When the amount of phosphorus added in the soils is 600 mg·kg-1, the amount of phosphorus adsorbed by soils is 451.2 550.8 mg·kg-1,its rate of phosphorus adsorbed is 75.2% 91.8%.The maximum buffering capacity and the free energy of phosphate adsorption are regarded as important indexes to evaluate the phosphate buffering capacity of soils. Regression analysis revealed that the maximum buffering capacity and free energy of phosphate adsorption has close relation to chemical and physical properties of soils.They generlly have positive relation to the pH value,the amount of clay and hygroscopic water of the soil.But they have negative relation to the contents of organic matter,available phosphate and total phosphate of the soil.Results also show that the fertiphos requirement of soil can be forecasted according to the phosphate adsorption and buffering capacity. It is significant for rational application of fertiphos.