COMPARATIVE STUDIES OF SOIL CHARACTERISTICS IN SHEA PARKLANDS OF GHANA

Abstract

An assessment of soil physical and chemical properties was carried out in Shea parklands of northern Ghana, selected along a North-south climatic gradient in 2011. The study sites were Paga, Nyankpala and Kawampe, which are located in the transitional and Guinea savannah zones of Ghana. For each site, 9 fallows and 9 cultivated fields were used, a total of 18 plots per site. Soil samples were collected at a depth of 0 to 30 cm and analysed for particle size distribution, pH, organic matter (OM), nitrogen (N), phosphorus (P), exchangeable bases, exchange acidity and effective cation exchange capacity (ECEC). The results revealed that the soils were strongly acid to neutral in reaction. The soils at Nyankpala parkland were comparatively more acidic (pH < 6). Generally, the pH values recorded were within the desirable range for plant nutrient availability. Levels of, OM, ECEC, and total exchangeable bases (TEB) were very low, and varied across the parklands, with Nyankpala parkland showing higher levels of OM and ECEC. In spite of the low pH, the soils were highly base saturated (PBS > 80%) and deficiencies of basic cations were uncommon. Land use did not significantly influence the soil chemical properties. However, N values, were significantly higher in old fallows than in respect of new fallows and cultivated fields. Soil particle size distribution especially at Nyankpala was significantly influenced by land use, with fallow lands having more proportion of sand than that of cultivated fields. The extremely low P content (trace – 7.11 mg/Kg) of the soils might be due to P fixation which was commonly reported for soils in northern Ghana. However, if these soils were supplied with N fertilizers, seedling regeneration would be promoted due to the fact that increasing N levels and decreasing P levels in soil, results in significant increase in seedling dry weight as well as increasing uptake of total shoot N and C