Vermicomposting of cattle manure and its performance as a fertilizer in maize production

Abstract

Growth in cattle population is associated with increased manure generation whose current management in low-income countries is associated with health and environmental problems, as well as low utilization rates. This trend can be reversed through promoting better manure management technologies. The objective of this study was to assess the potential of vermicomposting as one of the technologies in cattle manure management and use the harvested product as a fertilizer for growth of maize. A vermicomposting system using cattle manure and earthworms (Eudrilus euginea) was monitored for one year with harvesting of products (compost, earthworm biomass) every three months. Vermicompost samples from the beginning of the experiment and after every harvest were analyzed for the following parameters: pH, ash content, volatile and total solids, nutrients N, P, K, and C. Emissions of CO2, CH4, NH3 and N2O were also measured. Material flow analysis was used to determine the flows and retention of nutrients within the system. The harvested vermicompost was assessed as a soil amendment in comparison with other commonly used fertilizers namely: digestate; composted manure and inorganic fertilizer with maize as a study crop. Results showed that total solids, ash, N, P and K content significantly increased, while contents of volatile solids and C, as well as the pH, significantly decreased over time. Of the materials that entered the vermicomposting system, 46% went to vermicompost, 2% into earthworms, and 52% was lost to the atmosphere. Substance flow analysis showed that 30% of C went to vermicompost, 69% was emitted to the atmosphere and 2% ended up in earthworms while 75% of N was transferred to vermicompost, 7% went to earthworms and 18% escaped into the atmosphere. The cumulative emissions were 102 g CO2 kg-1 waste, 7.6 g CH4 kg-1 waste and 3.943 x 10-5 g N2O kg-1 waste on a dry basis, while NH3 was not detected throughout the measurement time. Maize performance in terms of height, ear and grain yield was significantly (p<0.05) improved with application of the fertilizers. However, among fertilizer treatments, no significant differences (p>0.05) were found between vermicompost and other fertilizer treatments. In general vermicomposting of cattle manure proved to be a better technology in terms of maintaining nutrients, reduction of greenhouse gases and provision of a fertilizer for maize growth