The steeply sloping mountainous topography, high rainfall and poor soil management practices in many of the Caribbean islands have caused excessive soil erosion by runoff. Most of the farmers on hillsides are resource-poor small-holders who do not have a soil conservation culture, and who have a limited formal education and training. There is an urgent need to develop methods of soil conservation which are simple, inexpensive and acceptable to the farming communities. The major function of the hedgerows is to increase the rate of water infiltration and impede surface runoff and transport of sediments, and thus retain nutrients in the cropping system.
An experiment was established in the Blue Mountains of Jamaica to investigate the consequences of secondary forest clearance for agriculture, and the effectiveness of the contour hedgerow system. Surface water run-off, soil erosion, rainfall interception and organic matter input processes and soil conditions were recorded in the first two years after forest clearance. The results show that considerable protection is offered to both the soil and water resources by the forest, even though it is of a secondary nature. In particular, the forest acts as a buffer against fluctuations in runoff associated with rainfall events, which is of significance in large-scale events, which cause considerable erosion. Agricultural use of cleared land does result in increased erosion, and the incorporation of hedgerows of Calliandra calothyrsus reduced runoff and erosion compared to the conventionally farmed plots. The presence of the hedgerows had a significant effect on soil conditions under the trees, but the effects were not distributed to the farmed areas between the hedgerows by two years after planting.
Correspondence: M.A. McDonald, School of Agricultural and Forest Sciences, University of Wales Bangor, Gwynedd LL57 2UW, UK