Initial impacts of forest tree based agroforestry system on soil properties of a degraded watershed

Abstract

The initial impacts of Forest Tree Based Agroforestry System (FTAS) on the characteristics of soils of a degraded pasture land were studied using a two factor factorial experiment in Randomized Complete Block Design. Factor A was combination of tree species (Gmelina arborea and Swietenia macrophylla) and spacing (2×2, 2×3, and 2×4 m) while Factor B consisted of three sampling periods (years 1, 2 and 3). Soil samples from the topsoil (0–15cm) and subsoil (15–30cm) were analyzed for soil pH, organic matter (OM), available phosphorus (P), exchangeable potassium (K), and cation exchange capacity (CEC) and bulk density (BD) from the top 0–5cm depth. Treatments significantly affected pH, P and CEC in the top soil and OM and K in the subsoil. Sampling significantly influenced pH and CEC at both depths and P in the subsoil. Interactions between treatments and sampling were significant for pH and OM in the top soil and P in the subsoil. Identified constraints in the rehabilitation of the site were soil acidity, P deficiency, low OM and BD. Although initial impacts showed positive trends towards rehabilitation of the soil, the short duration of the study was not enough to fully evaluate the impacts of FTAS. © 2006 Taylor & Francis Group, LLC.