Pedological and edaphological properties of benchmark acid soils developed on sedimentary and metamorphic rocks of north-eastern region under climatic predominance of humid tropic were studied. The soils are acidic (pH 4.0 to 5.6) and highly leached, having poor base saturation and low exchange capacity. They are characterized by high KCl-extractable aluminium (18 to 639 mg kg−1 soil) throughout the solum. Presence of low activity clay along with subsoil aluminium toxicity rendered them less fertile. Total potential acidity (extractable acidity) was as high as 59.5 to 92.5 per cent of total exchange capacity while the acidity due to variable charge (pH dependent) ranged between 7.3 and 31.9 cmol (p+) kg−1 contributing to 77 to 95.5 per cent of total acidity. The most spectacular difference among the soils was in extractable aluminium which discriminated the soils of Meghalaya as more weathered in the region. Application of lime would be an important management target for these acid soils. Lime estimates indicated that soils of Meghalaya require far less lime for correcting acidity.
Pedology, edaphology, benchmark soils, north-eastern region, extractable aluminium low activity clay, potential acidity, pH-dependent acidity, Taxonomy
