Soil organic matter and yield of forest and tree crops

Abstract

Three hundred and sixty eight soil samples collected from the surface layers of plantations of coffee (Coffea robusta) andGmelina arborea (a forest tree crop) were analyzed for organic carbon, total nitrogen and loss-on-ignition as the case might be. The aim was to investigate the direct influence of soil organic matter on the yield of tree crops in different ecological zones of Nigeria. Coffee yield collected at different harvests and total coffee yield were seperately regressed on soil organic carbon content. In most cases, positive regressions of coffee yield on soil organic carbon were recorded. Consistent positive correlations between each of indicators of soil organic matter and girth ofGmelina arborea were recorded in the order of organic carbon, nitrogen and loss-on-ignition. The relationship between C: N ratio and the performance of Gmelina depended on which of organic carbon and soil nitrogen was more influential at a particular location.