低分子量有机酸对红壤无机态磷转化及酸度的影响

以鄂南、赣北两红壤样品为材料，加入不同有机酸并经室温培养后，测定不同P组分、pH及活性Al含量的变化。结果表明，供试有机酸均使土壤Ca2－P含量增高，增幅大小依次为柠檬酸＞苹果酸＞琥珀酸＞乙酸；2种土壤的Ca8－P和Ca10－P含量无明显变化规律，Fe-P、Al-P和O－P含量有所下降，除乙酸处理的土壤pH值无显著变化外，其它有机酸的加入使pH下降0．65－1．96；有机酸引起活性Al量增多，除乙酸处理的变化较小外，其它有机酸或混合物的加入使土壤中0．02mol.L^-1CaCl2提取Al增加4．7－50．3倍，1mol.L^-1提取Al增加4．0－67．3倍。可见，有机酸具有双重作用，既增加P的有效性，又增加土壤酸度和Al毒。

Effect of low molecular weight organic acids on inorganic phosphorus transformation in red soil and its acidity

Red soil samples collected from southern Hubei province and northern Jiangxi province were tested to analyze their inorganic phosphorus fractions, pH and active aluminum after incubated with added various organic acids. The results indicated that application of organic acids increased the content of Ca2-P in both red soils, in the order of citric acid > malic acid > succinic acid > acetic acid, did not affect the contents of Ca8-P and Ca10-P, but usually reduced Fe-P, Al-P and O-P. The pH values of the soils treated by organic acids, except for acetic acid, were reduced by 0.65-1.96, compared with the control. Soil active Al extracted with 0.02 mol.L-1 CaCl2 in treatments with citric, malic and succinic acid was 5.7-51.3 times as the control, and Al extracted with 1 mol.L-1 KCl also increased 4.0-67.3 times. However, acetic acid had little influence on active soil Al. It was concluded that in red soils, organic acid could improve phosphorus availability, but enhance the soil toxicity caused by active Al.