华南红壤的交换性碱和交换性酸

EXCHANGEABLE ALKALINITY AND EXCHANGEABLE ACIDITY OF RED SOILS IN SOUTH CHINA

本文提出了一个同时测定土壤的交换性酸和交换性碱的简易方法。将土壤的交换性酸和交换性碱区分为:Na-交换性酸、Ba-交换性酸和SO_4-交换性碱、F-交换性碱。用推荐的方法,在野外对华南地区由不同母质发育的砖红壤、赤红壤、红壤等10个剖面进行了测定。结果表明,红壤类土壤含有相当量的交换性碱,但其数量比交换性酸少。酸性母质发育的土壤的交换性酸和交换性碱量大于由基性岩发育的土壤者。红壤的交换性酸和碱的量随电性盐浓度的增高而增大,浓度大于0.1N后,数量基本不变。

In this paper, a simple method for simultaneous determination of exchangeable acidity and exchangeable alkalinity of soils which could distinguish to Na-exchangeable acidity, Ba-exchangeable acidity, SO_4-exchangeable alkalinity and F-exchangeable alkalinity was proposed. The exchangeable acidity and exchangeable alkalinity of various red soils derived from different parent materials in South China were determined with the proposed method in the field. The results showed that acid red soils contained not only large amount of exchangeable acid but also considerable quantities of exchangeable alkali. Because Ba^(2+) ions possess a stronger power than Na^+ ions in replacing exchangeable aluminium ions, which are the principal cause of soil acidity, the amount of Ba-exchangeable acid was larger than that of Na-exchangeable acid. Likewise, because the amount of OH^- ions released by ligand exchange between F^- ions and hydroxyl groups on the surface of soil particles was higher than that when SO_4^(2-) ions were used, the amount of F-exchangeable alkali was larger than that of SO_4-exchangeable alkali. For the same type of soil, the amounts of exchangeable alkali of red soils derived from acid parent materials were higher than that of the soils derived from basic rocks. The amounts of exchangeable acidity and exchangeable alkalinity increased with the increase in neutral salt concentration up to 0.1 N, and then approached a constant value.