Optimization of Fly Ash Incorporation into Cow Dung–Waste Paper Mixtures for Enhanced Vermidegradation and Nutrient Release

This study was conducted to establish an appropriate mixture ratio of fly ash (F) to optimized cow dung–waste paper mixtures (CP) to develop a high‐quality vermicompost using earthworms ( Eisenia fetida ). Fly ash was mixed with cow dung–waste paper mixtures at ratios of (F:CP) 1:1, 1:2, 1:3, 2:1, and 3:1 or CP alone and composted for 14 wk. Olsen P, inorganic N (NO 3 , NO 2 , and NH 4 ), C:N ratio, ash content, microbial biomass C, and humification parameters were measured together with scanning electron micrograph images to determine compost maturity. Based on C:N ratio, the extent of vermidegradation of the waste mixtures followed the decreasing order (F:CP) of 1:3 > 1:2 > 1:1 > CP alone > 2:1 > 3:1. Similarly, Olsen P was significantly higher ( P < 0.05) where earthworms were added. The mean percentage increase in extractable P was in the order CP alone > 1:2 > 1:3 > 1:1 > 2:1 > 3:1, with earthworm addition almost doubling P release across the 1:1, 1:2, and CP alone treatments. Fly ash incorporation enhanced conversion of organic N to the plant‐available inorganic forms, with the 1:3 treatment resulting in the highest conversion. Scanning electron micrograph images confirmed the extent of vermidegradation reflected by the various humification parameters determined. Fly ash incorporation at the 1:2 ratio proved to be the most appropriate because it allows processing of more fly ash while giving a vermicompost with desirable maturity and nutritional properties.