Green technology for keeping soil-water-nutrient fluxes on cultivated steep land and climate change mitigation.

Abstract

Use of vetiver as a green technology can address African farmers’ ecological problems through protecting farmlands on steep lands. In addition, it offers the opportunity to integrate smallholders into the green economy as it sequesters carbon, keep water and nutrient fluxes within the system, sustain high crop yield with climate change adaptation potentials. This is particularly important as more slopes are converted to agricultural lands due to increase in population density and poverty. Thus, the study investigated the optimal strip width for increases in soil productivity and farmers’ preferences for space. The study planted maize and cassava in between vetiver field structures (VFS) installed on the contour at 5, 15 , 25 m apart and compared it with Farmers’ Practice (FP) on a 45 % slope and quantified the amount of soil displaced, water and plant nutrient losses and crop yields. Vetiver installed at 5 m surface interval spacing significantly enhanced carbon sequestration indicating potentials for GHGs mitigation and reduced N, P, Ca, Mg, Na and K losses when compared with FP. Vetiver allowed only 7 % rainfall lost as against 29 % on FP this demonstrates the climate change adaptation potentials of vetiver. Soil displaced under FP was 68 times higher than the soil loss tolerance limit of 12 t ha^-1 yr^-1 whereas under VFS at 5, 15 and 25 m it was 2½, 13 and 12 times higher. Maize grain yield were 35, 23 and 24 % higher on the VFS field at 5, 15 and 25 m respectively when compared to FP. The corresponding values for cassava fresh tuber were 43, 32 and 29 % higher. Unlike other technologies, vetiver grass contributes to the livelihood of the farmers by providing raw material for house thatching, handicrafts and fodder for livestock during lean seasons.