Charicteristics And Availability Of Inorganic Phosphate Fractions In Calcareous Soils Under Long-Term Fertilization

For long-term fertilization, the content of total phoshporus rises highly in calcareous soils. Because of the special physical and chemical properties and chemical activity of phosphate, the efficiency of phosphorus fertilization falls excessively, so that most phosphorus fertilizer changing to insoluble forms accumulated into abundant potential phosphate resource in soil. The objectives of this research were to analyze the fractionation and the availability of phosphorus in soil and to enhance the efficiency of phosphate fertilizer and to explore the phosphate resourse in soil, at the same time, to provide a scientific basis for utilization of insoluble phosphate fertilizer and technology of fertilization. The research discussed the different forms of phosphorus in calcareous soil, different fractionation methods, the enrichment and characteristics of different phoshorus forms, the correlation between the forms of phoshorus and microelement, variation of phoshorus at the exhausting condition and the availablity of phosphorus fertilizer in calcareous soils. The main results and conclusions were as follows:1. The amount of total P, availabile P, inorganic P, and organic P significiantly increased in calcareous vegetable soil more than those in calcareous crop soil for long-term fertilization. The amount of availibile inorganic P characterized positive correlation with years of planting significiently. The vertical distribution of different inorganic phosphorus forms in vegetable soil differed from these in crop clutivated soil significiantly. Different forms of phosphorus in cultivated soil characterized enrichment in surface horizon and falled down from the cultivated soil in the pedon abruptly. The content of Ca2-P, Ca8-P, Fe-P in vegetable soil characterized with enrichment in surface horizon and falled down from the cultivated soil in the pedon abruptly, and these of different horizons in vegetable soil were higher than those in crop soil. Although hose of A horizon were higher than that of lower horizon in the crop soil, vertical distribution of Ca2-P, Ca8-P, Fe-P in the soil profile charactered with falling down gradually. Diffluent P fractions such as Ca2-P,Ca8-P were highly correlated with the nutrition...