Urease Enzyme Activity in Surface Soils under Various Land use Types in Minna, Southern Guinea Savanna

The study sites were some vegetation types in Minna, Southern Guinea Savanna. The objectives of this study were to determine the activity of urease at surface soil depth under three vegetation types and to estimate the effect of vegetation types on physical, chemical, and biological properties of soil. Soil samples were collected diagonally on July 11 and 12, 2014, with the aid of sterilized auger, bulked, air dried, and screened through 2 mm and 0.5 mm sieves for physicochemical and biological properties determination according to standard methods. The treatments were three vegetation types (fallow, teak, and gmelina vegetation), at three soil depths (0–5 cm, 5–10 cm, and 10–15 cm), fitted into a completely randomized design having three replicates. The results obtained demonstrated that urease activity is an indicator of nitrogen status of soil. High urease activity may signify nitrogen stress. The higher the NH4-N volatilized, the higher the urease activity. Teak vegetation had the highest urease activity of 14.47 μg NH4-N/g of soil at depth 0–5 cm while fallow had the lowest of 0.82 μg NH4-N/g of soil at depth 10–15 cm. Low values (