Assessment of some important fertility parameters related to different land-use systems in the humid forest zone of southern Cameroon

Abstract

A field study was carried out in 1999 and 2000 in the village of Akok 180 km south of Yaoundé in the humid forest zone of southern Cameroon to assess changes in particle size distribution and soil chemical properties related to five different land-use systems namely: a secondary forest, a young forest, a cocoa farm, a Chromolaena fallow and a mixed food crop field. The results showed that land-use systems significantly affect the soil particle distribution and the highest proportions of sand and silt fractions were found in soils of young forests, the highest clay content was found under cocoa farms (P<0.0001). Soil pHH2O, exchangeable Ca and Mg, Al saturation and ECEC in the first, second and third 10 cm layers varied significantly with land-use systems (P<0.0001); organic carbon in the first and the second 10 cm layers significantly differ with the landuse systems (P=0.0115); and available P in the second and third 10 cm layers varied significantly with land-use systems (P<0.0007). Moreover cocoa farms had the highest pH, the lowest Al saturation, the highest soil Ca, Mg, ECEC and P contents compared to the other land-use systems. Based on their pH level and their high base saturation levels, soils of cocoa farms seem to present a higher fertility status than those of the rest of land-use
systems. It is assumed that permanent vegetation coverage and/or exposure to heavy rains of the soils, disturbances due to land preparation, organic matter supplied by the vegetation, nutrient cycling, nutrient
restitution and nutrient uptake could be differentiation factors.

Key words: Saturation, ECEC, particle size distribution, nutrient cycling, requirement.