Effect of stone retention walls on soil productivity and crop performance on selected hillside farms in southern Honduras

The following conclusions were drawn. (1) Terraces built with stone retention walls are effective in retaining topsoil. Plots with a combination of stone walls and mulch cover showed the least soil movement. (2) The shallow but fertile soils of the watershed are derived from basaltic parent material. At the present stage of terrace evolution, no significant decline in soil chemical properties has occurred. Unterraced plots at two sites showed a slight decline in soil organic matter. Soil organic matter content was found to be accumulating directly about terrace walls at all sites. (3) Terracing increased water storage capacity by maintaining greater topsoil depth, creating improved soil through deposition above the stone walls, and producing soils with reduced amounts of coarse fragments. (4) Terracing positively affected grain yield at two sites. Increase in production was attributed to more available water at both sites and to reduction of erosion at one site. (5) At all sites, production of above-ground biomass was greater on terraced plots. This demonstrates that the terraces provide improved growing conditions if soil water is not depleted below critical levels. (6) Problems concerning terrace wall stability arise as soil is redistributed within terraces. Many walls are not protected with vegetation as recommended. Failure to maintain these structures will reduce their effectiveness. Production is negatively influenced by the reduction in cropping area due to the space occupied by retention walls. (7) FAO guidelines do not recommend that terraces be constructed on slopes greater than 47%. The sites in this study, as well as many other farms in the Choluteca watershed, are at or above the maximum range of applicability for terracing. Further studies area needed to determine effective terrace widths as influenced by slope and soil characteristics. Similar studies should be undertaken concerning the use of vegetative barriers for soil conservation. (8) Farmers viewed their terraced plots are being more productive, but despite this fact, new walls are not being built. The high labor requirement is often cited as an obstacle. Lack of awareness of the long- term consequences of soil erosion may be another factor. It is recommended that the construction of stone retention walls and the planting of protective vegetation must be regarded as a community effort. (Author abstract, modified)