Variability of Soil Properties under Continuous Irrigation Farming in Nigerian Savanna

This study examined variability of soil properties under continuous cultivation in the Nigerian Savanna. Bulked soil samples were collected from eight irrigated farm plots and one uncultivated field during both wet season (WS) and dry season (DS) respectively. The samples were analyzed for Sand, silt, clay, bulk density, porosity, moisture content, pH, organic matter, total nitrogen, available phosphorus, exchangeable cations (Ca, Mg, K, and Na), exchangeable acidity (H+Al), exchangeable cation exchange capacity (ECEC) and base saturation which are the key soil fertility parameters. Percentage equivalence value of soil property was computed by expressing the mean value of each soil property in WS as a percentage of the mean value of the same property over the DS. From the results, the soil textural grades remained loamy in both seasons. The mean values obtained at topsoil during WS and DS are: sand (50.38 & 51.38%), silt (39.63 & 38.63%), clay (10% each), bulk density (1.38 & 1.42), porosity (47.75 & 64.04%), moisture content (0.26 & 0.19cm3 ), pH (5.7 & 6.03), organic matter (1.62 & 0.62%), total N (0.12 & 0.08%), available phosphorus (58.36 & 48.25mgkg-1), cations [Ca (7.76 & 6.17cmol/ kg-1), Mg (1.48 & 1.15cmol/kg-1), K (0.36 & 0.21cmol/kg-1), and Na (0.61 & 0.25cmol/kg-1)], H+Al (0.59 & 0.50cmol/kg-1), ECEC (10.63 & 8.26cmol/kg-1) and base saturation (93 & 92%). These results suggest that land use has both direct and indirect effects on the variability of soil properties.