The Impact Of Phosphorus On Soil Phosphorus Behavior

By field and cultivation experiments we studied the dynamic of inorganic phosphorus (Pi) in three soils applied phosphorus fertilizer at different levels, including the distribution characteristics of Pi fractions in different soil depth moved with filtration and on the soil surface moved with runoff. The result indicated:(1) Application of inorganic phosphorus fertilizer increased contents of all Pi fractions in soils. Contents of Al-P and S-P (extrated by 1mol/L NH4CI) in yellow brown soil and red soil and contents of Ca2-P and Ca8-P in saline soil improved remarkably, but there was relatively a less increase of Ca-P in yellow brown soil and red soil and Ca10-P in saline soil.Contents of Pi fractions in all three soils applied no P fertilizer fluctuated little during the cultivation period. Contents of Fe-P in red soil, Al-P and Fe-P in yellow brown soil, Ca2-P, Al-P and Fe-P in saline soil increased and then decreased. The fluctuation was obvious in the first 20 to 30 days and then stable contents reached. Contents of Al-P and Ca-P in red soil, Ca-P in yellow brown soil, Ca8-P and Ca10-P in saline soil presented an increase tendency in the early 20 to 40 days of cultivation and had little change later. Content of O-P in all three soils deceased in the early 40 days.After apllication of the phosphorus fertilizer, rates of S-P in yellow brown soil and red soil and Ca2-P in saline soil dropped suddenly with the cultivation course. Rates of Al-P and Fe-P in yellow brown soil, Ca8-P and Fe-P in saline soil increased first and then became stable after 20 to 40 days of cultivation. Rate of Al-P in red soil increased first and then decreased. Rates of Fe-P in red soil and Al-P in saline soil fluctuated and became steady after 40 days of cultivation. Rates of O-P in yellow brown soil and red soil fluctuated and tended to be steady after 30 to 40 days' cultivation, but that in saline soil rose slowly during the first 40days of cultivation and then increased suddenly. Rate of Ca-P in yellow brown soil dropped ant then rose but that of Ca-P in red soil and Ca10-P in saline soil fluctuated and tend to be steady.Total Pi content in red soil without phosphorus fertilization increases during cultivation period, that in saline soil only had little change, and that in the othertreatments presented a downward tendency. Increasing amount of total Pi content in red soil and saline soil decreased with the cultivation period, and that in yellow brown soil fluctuated.(2) Pi, the main form of soil phosphorus, took 80% of total P in the rice soil of Tai Hu region. Ca10-P took the domain place in Ca-P, the main part of soil Pi. Content of Olsen-P' was as low as less than 1%. Content of O-P, Fe-P, Al-P, Ca2-P and Ca8-Pdecreased with soil layer depth, that of Caio-P decreased and then increased with the soil layer depth.Long-term application of phosphorus fertilizer increased total P, total Pi, Olsen-P, and all fractions of Pi in the rice soil and had a most obvious impact on the top layer soil. Contents of total P, total Pi, Olsen-P, and Pi fractions (except Caio-P) decreased with the soil layer depth at all levels of P fertilizer application,but had no significant difference in 15-30cm and 30-45cm soil layer. Contents of O-P and Ca2-P in the rice soil apllied with 70 and 150 kg·ha-1 P fertilization and that of O-P with 30, 70 and 150 kg·ha-1 P fertilization were lowest in 30-45cm soil layer, but not in 15-30cm soil layer.(3) Between the amount of P fertilizer application and P content in runoff, there was an extremely significant positive correlationship. The more P fertilizer was used, the more P content in the runoff. After P fertilization particle P was the main form in the runoff at the beginning, and later content of soluble phosphorus increased considerably. At the general level of P fertilization organic P was the main form in the soluble P, but at high level Pi was.(4) Phosphorus fertilizer application raised the concentration of soluble P in soil solution at 30cm depth, but had little influence at 60cm depth, and had almost...