Effect of organic acids on the activation of phosphorus in vegetable garden soils
有机酸对菜地土壤磷素活化的影响

The increasing demand for food production throughout the world has been exerting growing pressure on mineral nutrient cycling in agricultural ecosystems. Lack of available phosphorus(P), for plant growth is a widespread limitation to agricultural production. It has been reported that only 8% of 500 soil samples, collected from 42 countries were classified as not deficient in phosphorus. The management of phosphorus nutrition in soil is one of the important agricultural practices. However, excessive application of phosphorus fertilizers may result in not only economic loss but also cause other environmental problems, such as severe eutrophication. Effects of low-molecular-weight organic acids on soil phosphorus release have been studied by a series of batch experiments. Many studies reported in the literature are only concernedwith the accelerating effects of organic acids on soil phosphorus release in agroecosystems. The aim of this study is to investigate whether low-molecular-weight organic acids can be used to predict the risk of P release in peri-urban areas, such as vegetable garden soils. Two organic acids (oxalic and citric acids) and nine vegetable garden soils were used, and the effects of different concentrations (0, 0.1, 0.5, 1.0, 1.5, 2.0mmol/L) of oxalic and citric acids on the release of phosphorus from these soils were carried out by soil incubation in laboratory. the kinetics of phosphorus release from soils was also studied. Results showed that the release of phosphorus by organic acids from vegetable garden soils is significant. The effects of low-molecular-weight organic acids on soil phosphorus release increased with increasing concentrations of organic acids. The release of soil phosphorus increased from 124.26mg/kg to 603.37mg/kg in No. 1 vegetable garden soil, with increasing concentrations of oxalic acid from 0.1mmol/L to 2.0mmol/L. Oxalic acid is better than citric acid for the release of soil phosphorus. There were significant correlation between the release of phosphorus by organic acids and soil Oslen-P and organic matter content. The release of soil phosphorus increased with incubation time. Soil phosphorus release increased from 248.32mg/kg at 0.5h to 989.45mg/kg at 8h for citric acid in No. 1 vegetable garden soil.