Oriented regulation of earthworm production and vermicompost quality by carbon bioavailability management

Abstract

Vermicomposting is an efficient bioconversion technology for recycling nutrients from organic waste materials. The biodegradability of raw materials has a significant impact on the earthworm transformation product. However, the management of carbon bioavailability is often overlooked during the vermicomposting process due to the varying degradability of C-rich source in different organic waste. This research aims to investigate the impact of different bioavailable carbon compositions on vermicomposting and to develop a strategy for efficient carbon management. The study involved systematic vermicomposting using four different biodegradable carbon sources (pineapple peels, rice straw, tomato straw, and sawdust) with varying carbon‑nitrogen ratios (ranging from 24 to 42). The earthworm production and vermicompost quality were comprehensively evaluated, along with the influence of carbon components on microbial community structure. The results indicated that the optimal vermicomposting treatments were achieved at PCM24, RCM30, TCM30, and MCM30 treatments. Maintaining an approximate ratio of 1:(0.5–1.3) between available and recalcitrant carbon components based on the optimal carbon‑nitrogen ratio was found to be optimal for regulating vermicomposting products. Increasing the proportion of available carbon enhanced the quality of vermicompost fertilizer, while a higher proportion of recalcitrant carbon could improve earthworm biomass production efficiency. Labile carbon proportion I (LCP1) and available carbon component (ACC) were identified as key indicators in influencing the formation of microbial community structure. Different carbon compositions led to the specific development and formation of microbial communities, further resulting in significant variations in vermicompost quality under the mediation of microbes. This study, for the first time, clarifies the impact of vermicomposting performance and microbial community from the perspective of carbon bioavailability, which is of great significance for the oriented regulation the vermicomposting efficiency and product in practice.