Abstract
Composting of municipal solid waste (MSW) is a good option of solid waste recycling, but the farmers are not interested to use MSW compost for raising crops because of its very low nutrient status. Thus, scope exists to enhance nutrient status of MSW compost through some organic amendments for its potential use as an organic fertilizer. The objectives of this study were to produce nutrient enriched MSW compost through some organic amendments, examine the N, P & S mineralization of amended MSW composts in soil, and evaluate the influence of amended MSW composts on rice and vegetable crops. Three types of amended compost were prepared by mixing 20% mustard oil cake (MOC) and 30% poultry manure (PM) or cowdung (CD) or sugarcane press mud (SPM) with 50% MSW compost and one unamended compost (control). Trichoderma viridi was inoculated to every type of compost. Such amendment increased the nutrient level of MSW compost. Respiration test, germination test and phytotoxicity bioassay had confirmed the characteristics of mature, stable and quality composts after three months time. Investigation of N, P and S mineralization from the amended composts was done through an incubation experiment at a fairly constant temperature of 25°C for 82 days under aerobic (field capacity) and anaerobic (1 cm water depth) conditions. The soil NH4+-N and NO3--N went to its peak within 2-3 weeks of incubation; the soil NO3--N was 2-3 times higher in aerobic condition than in anaerobic condition. Fitting the mineralization data to the first order kinetic model, N= No (1- e-kt) reveals that poultry manure and sugarcane press mud have higher capability to supply N for use by the crops. The enriched compost comprising MSW compost-MOC-PM in a 5:2:3 ratio demonstrated the highest cumulative N, P and S mineralization both in aerobic and anaerobic conditions. The control soil (no compost application) had the lowest nutrient availability. The present study clearly indicates a lower N and S availability accompanied with an increased P availability in submerged soils which has agronomic management implications in wet land rice cultivation. Field experiments were carried out at the Bangladesh Agricultural University farm, Mymensingh having silt loam texture, 6.7 pH and 2.79% organic matter. The experimental soil was Aeric Haplaquept under the order Inceptisols. There were 10 treatments consisting of chemical fertilizers (urea, TSP, MOP, gypsum & zinc sulphate) and four types of compost. Trichoderma viridi was used for MSW compost treatments (T3 - T10). The rate of all types of compost used was 10 t ha-1 alone or in combination of 50% recommended fertilizers to all crops. After one month, the different types of mixed composts (MSW + MOC + PM/CD/SPM) were applied to soil as per treatments design. The treatment effects were evaluated on brinjal (cv. BARI begun 1), cabbage (cv. Atlas 70), potato (cv. BARI Alu 25) and Boro rice (cv. BRRI dhan 28) in terms of growth, yield, yield components, nutrient (N, P, K & S) concentrations and changes in soil fertility. Yield and nutrient concentration (N, P, K & S) of all crops revealed significant effects of combined treatments were better than that of single fertilizers or single MSW compost. The treatment containing 50% fertilizers + 50% compost mixture (MSW + MOC+ SPM in a ratio of 5:2:3) performed the best result in all crops. There were apparent negative balances for N (11-45 kg ha-1) and K (6-48 kg ha-1), and positive balances for P (8-71 kg ha-1) and S (4-46 kg ha-1) in rice soils, across the treatments. The status of plant nutrients in soil increased due to application of enriched MSW at the rate of 10 t ha-1 to all crops. Results of this study have significant value in fertilizer management and recommendation strategies for cultivation of rice and vegetable
crops.