|ANGIMA, S - PURDUE UNIVERSITY
|O'NEILL, M - NEW MEXICO STATE UNIV
|OMWEGA, A - INTERMEDIATE TECH DEV GP
Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/28/2000
Publication Date: N/A
Interpretive Summary: Mechanically constructed terraces have been used for erosion control in Kenya's central highland region where traditional, non-mechanized farming is dominant. These terraces are difficult to maintain and viewed as a waste of valuable cropping land. In this region, farmers use napier grass as roughage for animals and as mulch material, and use Calliandra leaves, high in crude protein, for animal fodder and as green manure. This study was designed to test the feasibility of using hedges for natural terrace formation and as a source of biomass for feed and mulch. Test treatments included Calliandra tree hedge, napier grass hedge, combination tree and grass hedge, and control. First year, there were no differences in runoff. Soil losses were reduced by 50% and 33% with the Calliandra and combination hedges, respectively. The grass hedge didn't reduce soil loss because of poor stand establishment from drought. A survey of the plots showed a near uniform terrace formation and a 0.4% decrease in slope steepness for all hedges, while the control plots had a 0.4% increase in slope steepness. After full stand establishment, biomass productions were 5.3, 1.3 and 4.1 tons per acre for napier grass, Calliandra and combination hedge, respectively. This study showed the advantage of using Calliandra and napier grass hedges to initiate natural terrace formation and provide erosion control and animal feed. Additional advantages include improved land use efficiency, bio-diversity, resource conservation, and farmers' self-sufficiency. This study brings an important message to the soil conservation community: that the best conservation practices need to be derived locally, and should be based on needs and conditions of a specific region.
Technical Abstract: The erosion control strategy of using live barriers is potentially more beneficial and sustainable than mechanical earth structures. Our objective was to evaluate the use of a tree hedge alone or in combination with a grass hedge in controlling runoff and soil loss from an alfisol in central Kenya. Runoff, soil loss, and biomass from the vegetative strips were measured during two cropping seasons. Average cumulative soil losses from plots with hedges of tree, combination, grass, and non-hedged control were 5.6, 7.4, 11.2, and 10.9 t ha*-1 respectively. Total dry matter yields 11.90, 9.24, and 2.98 t ha*-1 yr*-1 for grass, combination, and tree hedge respectively. Topographic survey of the plots showed a near uniform terrace formation and decrease in slope of 0.4% for all hedges, but an increase in slope for the control plots by the same magnitude.