No abstract

Changes in soil physical and chemical properties associated with different land uses including natural savannah were compared in Nigeria. The study was conducted on large unreplicated sites. There was a significant coarsening of texture, depletion of organic matter and nutrients and increase in bulk density under Eucalyptus camaldulensis and Mangifera indica (mango) plantations, and also under arable and fallow conditions compared with under natural vegetation. The soil conditions were slightly better under Mangifera than under Eucalyptus, and in the fallow land than the arable land and tree plantations, but the differences were mostly non-significant. The land uses studied were less efficient than the natural savannah in protecting the soil from loss of organic matter and nutrients by offtake or surface washing. The options open to Nigerian smallholder farmers are discussed in relation to sustaining soil fertility and productivity.

No abstract

On the outskirts of Zaria, northern Nigeria, Eucalyptus camaldulensis and Pinus oocarpa plantations have been established to satisfy both land rehabilitation and agroindustrial objectives. Soils of the plantations and adjacent unafforested degraded sites where major in¯uences from soil type and management were minimal were sampled to provide data for a parallel investigation of the effect of afforestation on soil rehabilitation. Three adjacent age±grade plantations in respect of each tree species were involved. These are 6, 13 and 27 years for eucalyptus, and 7, 15 and 25 years for pines. Results obtained showed that the rate of soil regeneration in the context of present silvicultural practices is extremely slow. Of the soil parameter studies, only organic matter shows signi®cant improvement within the examined time frame. The soil texture, bulk density, in®ltration rate, nutrient elements and pH showed only slight improvement. There was little evidence to suggest that either of the tree species had a more bene®cial effect on the soil than the other. The signi®cance of the results is discussed in terms of land-use decision and policies in Nigeria towards a sustainable afforestation programme.

No abstract