Fertility Status and Forms of Acidity in Soils of Tuensang District, Nagaland in Relation to Land Use Systems

Abstract

Ninety six soil samples (48 each from cultivated and forest land use systems) were collected from sixteen villages of Tuensang district of Nagaland and analyzed for some important physicochemical properties, fertility status and forms of acidity. Soils were strong to moderate acidic in reaction, and those from cultivated ecosystem were more acidic. The cation exchange capacity (CEC) of the soils was quite low. The soils from forest land use indicated more CEC than those from cultivated land use system. Average sand, silt and clay contents of the soils of cultivated and forest ecosystems were 41.6 and 40.4, 27.3 and 27.7 and 30.3 and 30.9%, respectively. Lime requirement (LR) of the soils was high and soils of cultivated land use system indicated more lime requirement. Lime requirement had significant negative correlation with pH and positive correlation with organic carbon (OC) and forms of soil acidity. The soils were high in OC, medium in available nitrogen (N) and potassium (K), low in available phosphrous (P) and low to medium in available sulphur (S). Nutrient index of OC, N, P, K and S of the soils under cultivated and forest land use were 3.00 and 3.00, 1.96 and 2.00, 1.23 and 1.63, 2.00 and 2.00 and 1.48 and 1.85, respectively. Higher amount of OC, available N, P, K and S were reported in the soils of forest ecosystem. Total potential acidity of the soils was quite high and accounted for severe acidity problem in these soils and ranged from 7.4 to 15.5 and 7.1 to 15.7 cmol(p+)kg-1 in the soils under cultivated and forest ecosystems, respectively. The extractable acidity, pH dependent acidity, exchange acidity, exchangeable aluminium (Al) and exchangeable hydrogen contributed 38.0, 93.7, 20.7, 15.1 and 5.5% in cultivated land use system and 27.3, 74.2, 13.3, 9.0 and 4.2% in forest land use system to total potential acidity, respectively. Most of the components of acidity were significant and positively correlated with OC and CEC. Significant negative correlation was found between different forms of acidity and soil pH.