Effect of Organic Wastes and Method of Composting on Compost Maturity, Nutrient Composition of Compost and Yields of Two Vegetable Crops

Abstract

ABSTRACT Two field experiments were carried out to evaluate the effect of composts prepared from different organic waste materials on two vegetable crops. Poultry litter with each of the following organic wastes, maize residues, leaf litter, urban waste, weed biomass and soybean residue, were composted using three methods of composting–Passively Aerated Composting Technique in a pile (PACT-1), Passively Aerated Composting Technique in a plastic pot (PACT-2) and Windrow (Wdr). Tomato (Lycosipercum esculentum Mill.) and amaranthus (Amaranthus cruentus) were planted as test crops. The C:N ratio and nutrient concentrations varied with type of organic waste materials. The leaf litter and weed biomass contained high C:N ratio (38 and 45, respectively) and therefore produced composts that matured a few weeks later than those from organic wastes with C:N ratio falling within the optimum range of 25-35. The C:N ratio of the organic wastes were highly reduced at the end of composting. Irrespective of method used for composting, N in the soybean-based compost increased by 37-71% over the concentrations in the other composts. Phosphorus in the leaf litter- and soybean-based composts increased by 13.6-34.9% over the level in the urban and weed-based composts. However, K levels in the maize- and weed-bio-mass based composts increased by 7-37% over other composts. Soybean- and leaf litter-based composts in general were greater in both secondary and micronutrient elements than other composts. The results from field evaluation indicated that the effectiveness of the composts on amaranthus productivity can be rated in the ascending order of soybean, leaf litter, weed, maize and urban waste composts. For tomato, the composts from maize and soybean residues were more effective than other composts. Mostly, the effectiveness of the composts on the productivity of the vegetable crops varied according to methods of composting and followed in the ascending order of Wdr, PACT-1 and PACT-2.