The Age-Induced Quality Shift of Vermicompost Influenced the Biodegradation Kinetics in Soils

Abstract

ABSTRACT A study was conducted to identify the effects of aging on the biodegradability of vermicomposts in soil. Two solid wastes, including cow manure (CM) and wheat residues (WR), were subjected to the vermicomposting. The products of the various ages were mixed with Lavark and Langroud soils and incubated for 45 days. Results indicated that the aging effects led to an increase in the lignin (LG) content. Potentially, mineralizable C was decreased from 5308 mg C kg−1 for fresh substrates to 1643 mg C kg−1 for aged CM vermicompost in the Lavark soil. The decreasing trend was also observed for the Langroud soil. Similar behavior was also shown for the soils when treated with WR vermicomposts of different ages. The age of vermicomposts was negatively correlated with potentially mineralizable C as well as LG and C/N ratio. Multiphase decomposition was observed, in particular when the products of the early ages were used. The aging of CM and WR induced a decrease in the number of decomposition phases. Overall, by aging, the less biodegradable fraction (lignin) accumulates, and the patterns of decomposition tend to decrease the number of decomposition phases or decrease the last phase biodegradation rate constant.