Assessment of Variability in the Quality of an Acrisol under Different Land Use Systems in Ghana

Abstract

Three land use types (natural fallow, Leucaena leucocephala woodlot and cultivated plots) on a Ferric Acrisol in a semi-arid tropical zone of Ghana were compared to assess their effects on variability in selected soil properties and plant biomass accumulation. Organic carbon accumulation in the representative natural fallow profile was 22.7 g/kg, followed by 16.5 g/kg for the Leucaena woodlot and lastly 11.8 g/kg for the cultivated site. The mean bulk density of the natural fallow, Leucaena woodlot and cultivated sites were from 1.36 Mg/m 3 , 0.92 Mg/m 3 and 1.33 Mg/m 3 with corresponding range in mean weight diameter of 0.5 mm -1.2 mm, 0.6 mm -1.2 mm and 1.0 mm -1.2 mm, respec-tively. The lower bulk density observed for the woodlot corresponds to increased total porosity, aeration, and root pro-liferation due to the stronger and extensive rooting system. Significant differences (P < 0.05) in bulk density, mean weight diameter (MWD), clay content, organic carbon and total nitrogen existed among the land use types. Variability in pH and bulk density of the surface soils was less than 15%, in the three land use types. Generally, clay content and exchangeable Na recorded the highest variability (≥36%). For the surface soils, exchangeable Na was very variable in the natural fallow. Exchangeable Na, Ca and K and total nitrogen were very variable in the Leucaena woodlot and the cultivated sites. Variability in clay content was very high in the cultivated soils only. The order cultivated land > Leu-caena woodlot > natural fallow was noted for properties with high variability (CV ≥ 36%). Plant biomass accumulation was 1834 kg/ha (natural fallow) and 830 kg/ha (Leucaena woodlot) indicating that natural fallows do not only maintain soil quality but they also decrease variability in soil properties which is desirable for soil productivity and quality.