A study of design,construction and bank stabilization of fanya juu terraces at Kabete, Kenya

Abstract

The application of fanya juu terraces for soil and water conservation in high and low rainfall areas is on the increase, Fanya juu terraces have become popular because they are easy to construct, less infertile subsoil is exposed during the construction and when compared to bench terraces, less labour is required for construction. But for fanya juu terraces to be effective, proper design, bank stabilization and maintenance are necessary. The study of design, construction and stabilization of.fanya juu terraces was carried out at the University of Nairobi's Faculty of Agriculture Farm at Kabete, Kenya. between 18-10.82 and 18-1-83 on nitosol soils. The· suitability of the design of fanya juu terraces for retaining maximum runoff expected in specified period of time put forward by Thomas et al (1980) was studied. Labour required for the construction and land taken up by terraces were also studied. Seven grass species were planted on the banks of the constructed terraces. These species were visually evaluated for establishment and ground cover at the end of the project. Stone wall was the control. From the study, it was observed that the expression formulated by Thomas et al (1980) give8 a good guidance for designing fanya juu terraces. But data on infiltration and rainfall intensity is necessary. If the construction of fanya juu terraces is phased over a period of time, the labour requirement can be within the capabilities of small scale farmers. Average land lost from crop production in (i x l construction of fanya juu terraces was found to be 15%. If this area is used for bana grass production - a species which was observed to be high herbage yielder, about 45 t/ha green fodder can be obtained. This can be fed to livestock. Bank protection, stabilization and maintenance were observed to be necessary for fanya juu terraces.