Organic waste recycling by vermicomposting amended with rock phosphate impacts the stability and maturity indices of vermicompost.

Abstract

Recycling organic waste can help the land be nourished, properly disposed of, and protected from the negative impacts of chemical fertilizers. Organic additions like vermicompost can help restore and preserve the quality of the soil, however, producing vermicompost of a high enough standard is difficult. This study was planned to prepare vermicompost by utilizing two different organic wastes viz. household waste and organic residue amended with rock phosphate and further evaluate their stability and maturity indices during vermicomposting for quality of produce. For this study, the organic wastes were collected and vermicompost was prepared by using earthworm (Eisenia fetida) and with or without enriching with rock phosphate. Results showed that pH, bulk density, and biodegradability index were decreased and water holding capacity and cation exchange capacity was increased with the gradual progress of composting starting from 30 to 120 days of sampling/composting (DAS). Initially (upto 30 DAS) water-soluble carbon and water-soluble carbohydrate increased with rock phosphate enrichment. The population of the earthworms and enzymatic activities (CO₂ evolution, dehydrogenase, and alkaline phosphatase) were also increased on enriching with rock phosphate and with the progression of the composting period. Rock phosphate addition (enrichment) also reflected the higher content of phosphorus (106% and 120% for household waste and organic residue, respectively) in the final product of vermicompost. The vermicompost prepared from household waste and enriched with rock phosphate showed greater maturity and stability indices. Overall, this can be concluded that the maturity and stability of vermicompost depend on the substrate used and improves on enriching with rock phosphate.Implications: Our study concludes that the quality of vermicompost depends on different substrates, composting period, and enrichment with rock phosphate. The qualities of vermicompost were best found under household waste-based vermicompost enriched with rock phosphate. The efficiency of vermicomposting process using earthworms was found maximum for enriched and without enriched household-based vermicompost. The study also indicated that several stability and maturity indices are influenced by different parameters and hence cannot be determined by a single parameter. The addition of rock phosphate increased the cation exchange capacity, phosphorus content, and alkaline phosphatase. Nitrogen, zinc, manganese, dehydrogenase, and alkaline phosphatase were found higher under household waste-based vermicompost relative to organic residue-based vermicompost. All four substrates promoted earthworm growth and reproduction in vermicompost.