Optimization of Compost Maturity of Coffee Waste Mixed with Agricultural Wastes and Evaluation of Their Effect on Growth of Lettuce (Lactuca Sativa)

Coffee pulp and husk are the main by-products generated by the coffee processing plants and are disposed into arable land and surface water causing environmental pollution.Therefore, the major objectives of the present study were to optimize compost from coffee husk as organic fertilizer for cultivation of lettuce and to determine physico-chemical properties of compost during the decomposition periods.Coffee husk + Cow dung, Coffee husk + Poultry manure and Coffee husk + Desmodium triflorum in 3:1 (v/v) ratio were used to prepare the compost.The physicochemical parameters were determined for all the treatments during the composting periods.Temperature value at 0 day of composting was 28°C and then rose to thermophilic phase on 15, 30, 45 and 60 days.Finally at 90 days Temperature was at 35°C for each coffee husk and supplemented materials respectively.The pH values at day 0 were between 8 and 9, and finally at 60, 75 and 90 days were between 8 and 8.5 for each coffee husk and supplemented materials.The organic carbon and nitrogen content of the compost mixes: coffee husk + Desmodium triflorum, Coffee husk + Cow dung and Coffee husk + Poultry manure were 529.02, 500.05,517.92 and 0.05, 0.1, 0.053, respectively during 0 day of composting, whereas at 90 days the values were 248.18, 265.91, 239.68 and 0.001, 0.002, 0.0002, respectively.The mature compost had natural soil odor and brown in color.Mean values of germination percentage of lettuce during the composting periods at 0, 30, 45, 60 ,75 and 90 days were 11.71, 24.53,25.83,29.02, 46.47 and 56.37 respectively, whereas mean values of marketable yield of lettuce were 27.27, 28.87, 31.61,35.02, 40.59 and 57.67,g/plant respectively.Addition of 10% of coffee husk compost with 90 % of top soil significantly increased seed germination and yield of lettuce indicating the suitability of bioconverted organic substrates for vegetables cultivation.