Agro-processing by-products management by utilization: the case of coffee husk composting in south western Ethiopia

Abstract

Management of Agricultural byproducts, such as coffee husk, in developing countries is challenging due to their high transportation and handling costs and hence becoming major sources of environmental pollution. The commonly practiced management options, such as mulching and conventional composting, have several limitations. Therefore, the use of earth worms, and Effective Microorganism (EM) as a solution in coffee husk composting were hypothesized to be efficient in reducing compost maturity period while increasing the final compost quality. It was also hypothesized that coffee husk vermiwash enhances plant growth attributes depending on the rates used. In this study, two independent experiments were conducted from March 01-April 30, 2012. The first experiment was conducted to evaluate the effect of coffee husk compost types and their rate of application on seed germination and seedling growth of two commercially important tree species, Moringa stenopetala (Bak.) and Jatropha curcas (L.). The second experiment was conducted to evaluate the effect of coffee husk vermiwash at different concentrations on seed germination and seedling growth of the two species. For the first experiment, three factors were tested: Factor1, compost type (vermicompost (CHVC), EM compost (CHEMC), and conventional compost (CHCC)); factor 2, plant species (M. stenopetala, and J.curcas), and factor 3, compost rate (0, 10, 20, 30, and 40 %(v/v)). The experiment was arranged in 2x3x5 factorial in three blocks. For the second experiment, coffee husk vermiwash (CHVW) concentration at five levels was tested on two plant species in 2x5 factorial in three blocks. Both experiments were made with randomized complete Block Design (RCBD). Seedling growth attributes were recorded as response variables in both experiments. The results revealed that incorporation of the three compost types significantly (P<0.0001) improved the soil physico-chemical properties. Similarly, incorporation of the three compost types significantly enhanced all seedling growth parameters. Chlorophyll a and b were significantly higher due to CHVC application in M.stenopetala, which was statistically at par with CHCC and CHEMC, and J.curcas due to CHVC and CHEMC. The highest plant height was recorded from CHCC application. Maximum leaf number (7.05) and stem girth (6.83) were also observed from CHVC application. Irrespective of coffee husk compost (CHC) types, J. curcas showed the highest shoot fresh weight at 30 and 40 % and shoot dry weight at 20, 30, and 40 % (v/v) compared to non amended control. Application of CHVC at 40 % rate gave the maximum seedling root length of both species. Application of CHC at 20 and 30 %( v/v) rate enhanced root dry weight, but the value declined beyond 30%. Foliar spray of CHVW at 30 and 40 %(v/v) significantly (P<0.0001) contributed to maximum value of leaf chlorophyll b, plant height , stem girth thickness, shoot dry and root fresh weight. In conclusions, coffee husk vermicompost improved most of the soil physico-chemical properties and significantly improved the growth of seedlings compared to the other two composts. Utilization of CHVW foliar spray at 30 and 40 %( v/v) was found to be an economical. Therefore, coffee husk compost, which demands low labour and simple technology input, can be an opportunity in coffee growing areas of the country for better seedling growth and production in nurseries. Finally in order to enhance the microbial decomposition and ensure sustainable utilization of coffee husk while reducing environmental pollution, incorporation of bulking agents in vermicomposting and nutritional quality analysis of vermicompost and vermiwash need further study.