Competition in tree row agroforestry systems. 2. Distribution, dynamics and uptake of soil inorganic N

Abstract

The effect of tree row species on the distribution of soil inorganic N and the biomass growth and N uptake of trees and crops was investigated beneath a Grevillea robusta A. Cunn. ex R. Br. (grevillea) tree row and Senna spectabilis DC. (senna) hedgerow grown with Zea mays L. (maize) and a sole maize crop, during one cropping season. The hypothesis was that a tree with a large nutrient uptake would have a greater competitive effect upon coexisting plants than a tree that takes up less and internally cycles nutrients. The field study was conducted on a kaolinitic Oxisol in the sub-humid highlands of western Kenya. Soil nitrate and ammonium were measured to 300 cm depth and 525 cm distance fro..