Multi-omics insights into the vital role of thermophilic phase on compost maturity

Immature manure contains extremely higher phytotoxicity, which impedes the maturity and safe utilization of compost in farmland. Composting technology can efficiently reduce phytotoxicity, germination index (GI) is an authoritative index of compost phytotoxicity. Consequently, livestock manure composting was conducted to investigate the impact of composting process on phytotoxicity and its consequential effects on seed germination inhibition. Results show that fresh manure disrupted radicle cell structure and antioxidants enzyme activities, activated endogenous phytohormones in radish seeds, ultimately resulting in failed germination. In comparison to the control group (seeds cultured in deionized water), seeds cultured in initial compost aqueous extracts exhibited 14,679 differentially expressed genes (DEGs) and 1091 differential abundance proteins (DAPs). However, after the thermophilic phase of composting (Day 7), the number of DEGs decreased by 83.40%, and DAPs decreased by 64% in cultivated seeds. Notably, over 70% of down regulated proteins in initial were found to recover after the 49-day composting, with the majority of these recovered proteomes enriched in ribosome and carbon metabolism pathways. Furthermore, fresh manure exerted fatal and irreversible inhibition on seed germination. However, after the thermophilic phase (7 days), the inhibition of seed germination transitioned from irreversible to reversible and recoverable. The results underscore the pivotal scientific significance of the thermophilic phase in the composting process, which is crucial for the safe and efficacious utilization of manure-based fertilizers in agricultural practices.