The Effects of Soft Leaching with Low Molecular Weight Organic Acids on Soil P Release Characteristics

A soil column leaching experiment was conducted to investigate the influence of citric, oxalic and acetic acid on release characteristics of phosphorus. The results showed that for 5 mmol/L organic acid concentration, the ability of three organic acid to activate phosphorus in the soil was at the order of: citric>acetic>oxalic acid. Different treatments result in various phosphorus release characteristics. For citric acid treatment, phosphorus concentrations of effluents increased with effluent volume at the begining, there was a comparatively steady state at high level during 1000-3050 ml leachate volume after reached the highest value, then P concentration declined and became lower than the detection limit finally. For the oxalic acid, a regular decrease of P concentration was observed during the column leaching, and it droped to extremely low concentration rapidly. During the column leaching with acetic acid, the amount of P in the effluents initially increased, and then declined gradually. Though Pmaxand Pmax/T are not significantly higher than the values of oxalic acid treatment and CK, acetic acid treatment showed a relatively strong sustainability during column study. The variations of pH during column leaching with citric, oxalic and acetic acid followed the trend: citric>acetic>oxalic acid, which is the same as the order of the mobilizing ability of organic acids for phosphorus.