EVALUATION OF THE QUALITY OF AN ACRISOL UNDER THREE LAND USE SYSTEMS IN THE SOUTHERN SAVANNA ZONE OF GHANA.

ABSTRACT

A Ferric Acrisol (Toje series) under three land use systems namely, natural fallow (forest), a Leucaena leucocephala woodlot and a cultivated plot were studied. Soils from profiles and surface horizons were evaluated to determine the effect of management systems on variability in soil properties and soil quality. A combination of field study and laboratory analyses was carried out. In all, 15 profile samples and 75 grid samples taken from a 12 m x 12 m area at intervals of 3 m each between grid points were collected for analysis on selected physical and chemical properties. Another 30 grid samples were collected for the determination NH4+ -N and NO3- -N. Aggregate stability used, as a physical quality indicator, revealed that aggregates of the forest soil were the most stable followed by the woodlot as a result of organic matter addition from litter fall from the trees. Organic matter build up was in the order forest fallow> woodlot> cultivated (organic carbon content of 16.7 g/kg, 8.6 g/kg and 7.0 g/kg, respectively). Generally, all the soils had higher organic matter content in the surface horizons which decreased decreasing with depth in the profile. The cultivated soil had a soil quality index (SQI) of 33.3% which implied that its quality was 66.7% less than the maximum quality. The SQI of the woodlot was 50% which was more than the cultivated soil by 16.6%. The forest soil had an SQI of 61.1%, which was 27.8 higher than that of the cultivated soils. All the soils had low nutrient levels due to the presence of low activity clays inherent in them. The study revealed that the natural fallows (forest soils) had higher soil quality as well as lowest variability in soil properties.