Soil Nutrients Flow In A Tropical Semi-Deciduous Forest Ecosystem In Ghana
Primary and some secondary nutrient labile fractions concentrations of dissolved soil nutrients (Ca, Mg, K, N. Av. P and NO) were determined in cocoa plantation (DC), secondary forest (DS) and primary forest (FB) land uses in Dwinyan watershed in Ghana. Zero-tensioned lysimeters were buried at 0-15, 15-30 cm, 30-45 cm and 45-60 cm soil depths in the three land uses during the rainy season (March-September). The soil remained relatively moist throughout the study period. The highest soil moisture values recorded for DC and DS land uses were higher than that for TB. The primary forest exhibited a gentle rise and fall of its soil moisture. The volumes of soil leachate at monthly harvests in the land uses were higher in the 0-15 cm soil depth and highest for TBfollowed by DC and DS was least. Movement of Ca in solution in the land use was highest in DC (190 mg ml-I)at 0-15 cm soil depthfollowed by DS (174 mg m[-I) at 0-15 cm. Magnesium was highest in the DC (61 mg ml-I) at 0-15 cm followed by DC (33 mg m[-I) at 45-60 cm. Whilst N concentration in DC decreased with increasing soil depth, N03 increased with increasing soil depth. Available
P showed the trend for N except in TB where at 0-15 cm lower P concentration was recorded for the other soil depths. Potassium did not show a clear pattern. In DC and TB land uses, the trend of nutrient insolution was Ca > Mg > N03 > K > N> P and in DS, Ca > Mg > N03 > N> K> P The variation in soil moisture regime due to different quantities of precipitation and litter build up at the soil urface may greatly influence concentrations of mineral nutrients to flow in soil solution to fertilize lowlands.
Keywords: Landuse, leachate, nutrients, watershed, zero-tensioned lysimter