A COMPARATIVE STUDY OF SOIL PROPERTIES UNDER DIFFERENT SOIL MANAGEMENT PRACTISES IN LAFIA REGION, NASARAWA STATE, NIGERIA.

YUSUFU, F.A. AND ABENU, A.

Soil properties under different soil management practices (tree plantations, arable crops and natural vegetation) were studied, to highlight changes that occur in soil quality when lands are converted from natural vegetation to cultivated land. One hundred and fifty soil samples were randomly selected and analyzed for bulk density, pH, organic matter, available phosphorus, total nitrogen, exchangeable sodium, exchangeable potassium and cation exchange capacity (CEC). The results showed mean values for bulk density ranged from 1.2g/cm³ - 1.5g/cm³ at topsoil, the highest value was found under orange while natural vegetation had the lowest bulk density. The range of values for the bulk density increased slightly at the subsoil (1.3g/cm³ - 1.6g/cm³), with natural vegetation still having the lowest value. Natural vegetation had pH values that were close to neutral while other crops were slightly acidic. Organic matter (1.0% - 6.3%) was rated very low to medium, total nitrogen (0.04% -1.1%) was rated very low to very high, exchangeable sodium (0.1 cmol/kg - 0.4 cmol/kg) rated low, potassium (0.1 cmol/kg - 0.5 cmol/kg) was rated medium to high and CEC (1.9 - 8.8) was rated low to medium with natural vegetation having the highest mean values at both top soil and sub soil. While there was a general decline for values of organic matter, nitrogen, exchangeable sodium, exchangeable potassium and CEC with increased depth under natural vegetation and the tree crops, for arable crops the decline was only observed for organic matter and potassium with increased depth. Available phosphorus increased with increase in soil depth under arable crops and orange, while a decline was observed under natural vegetation and cashew. To improve soil nutrients and promote continuous farming, farmers should combine the use of crop residue, fertilizers and cropping systems such as crop rotation and agroforestry.

Key words: Arable crops, Natural vegetation, Soil properties, Tree plantations