Kinetics of phosphorus fixation and availability in acid sulfate, inland iron toxic and neutral soils.

摘要

The study was conducted to trace the mechanisms of phosphate fixation and availability in untreated, limed and leached acid sulfate soils and in inland iron toxic and neutral soils. Phosphate levels in different forms, along with other soil and water properties, were periodically monitored and compared among treatments. The results indicated different levels of P fixation with varied proportions of Fe, Al and Ca-P forms under different treatments. The total fixation of P was highest and comparablein limed acid sulfate and in neutral soil but lowest in leached acid sulfate soil. Among different forms, Al-P was proportionately largest in untreated acid sulfate and in iron toxic soils whereas Ca-P was largest in limed and leached acid sulfate and inneutral soils. Iron-P and Al-P were dominant in iron toxic soil while, the Ca-P was highest in neutral soil. Neither liming nor leaching of acid sulfate soil could reduce P fixation by Al. Liming helped to decrease Fe-P, but failed to increase P availability owing to P fixation by Ca. Leaching yielded more available-P because it reduced Fe-P, without affecting Ca-P level. Hence, leaching was more effective than liming for improving P availability in acid sulfate soil.