Forms of Acidity in Soils Developed on Different Landforms along an Altitudinal Sequence in Nagaland, India

Abstract

The present investigation characterizes different forms of soil acidity in surface soils along an altitudinal sequence of Nagaland state of India and their relationship with soil properties. One hundred surface soil samples were collected from four distinct landforms viz., highly dissected high hills (>2000 m above mean sea level, MSL) with very steep slopes (>33%) (HDHH), medium and lower hill ranges (1000-2000 m above MSL) with steep slopes (15-33%) (MLH), moderately dissected piedmonts (500-1000 m above MSL) with moderately steep slopes (10-15%) (MDP) and inter-hill valleys (<500 m above MSL) with gentle slopes (3-5%) (IHV). The soils had dominance of pH dependent acidity followed by exchangeable acidity in all the landforms. Significant correlation was observed between organic carbon (OC) and pH dependent acidity (r = 0.83**) and exchangeable aluminium percentage and exchangeable acidity (r = 0.91**). High OC content in hills and piedmonts due to abundant forest vegetation is likely to generate more variable charges and responsible for high pH dependent acidity, whereas, high aluminium saturation in soil due to rapid weathering of aluminium rich parent material is responsible for exchangeable acidity. The exchangeable aluminium percentage appeared to be a reliable indicator of soil acidity.