Nature of soil acidity as influenced by climate and topography in Some Ultisols and Alfisols of Orissa

Some Ultisols and Alfisols representing the Eastern Ghat area of Orissa were studied for the nature of soil acidity as influenced by climate and topography. The pH-dependent acidity varying from 4.7 to 16.4 cmol (p+) kg−1 was mainly associated with inorganic fractions of soil like Fe oxides and clay. The potential acidity in these soils varied from 5.3 to 16.6 cmol (p+) kg−1 and showed higher values in soils of higher altitude as compared with the soils occurring at lower altitude. All the soils exhibited decreasing acidity with depth irrespective of the altitude. The potential acidity showed significant positive correlations with Fe oxides, clay and organic matter. The pH-dependent acidity made a major contribution towards the potential acidity.