Studies of different forms of iron and aluminium in relation to nature of soil acidity in two Ultisols and an Entisol of Arunachal Pradesh.

摘要

The nature of acidity in relation to different forms of iron and aluminium of fourteen acid soils representing Ultisols and Entisols from Arunachal Pradesh, India, were characterized. The mean contents of iron and aluminium were extracted by various extracting reagents and were found to be in a decreasing order: dithionite > oxalate > pyrophosphate > ammonium acetate > KCl. The electrostatically bonded EB-H+ and EB-Al3+ acidity constituted 20.6 and 79.4% of exchangeable acidity, while EB-H+, EB-Al3+, exchangeable and pH-dependent acidities comprised 0.23, 1.05, 1.28 and 98.7% of total potential acidity. Different forms of acidity showed significant correlation with pHw, pHk and CEC. Although different forms of Fe and Al are responsible for most of the variations in different forms of soil acidity, the effect of different forms of Al is more pronounced and directly related with the different forms of acidity.