Effect of Lignite Addition on Maturity and Bacterial Community Assembly in Co-Composting of Goat Manure and Corn Straw

This study investigated the effect of lignite addition on maturity acceleration and bacterial community assembly mechanisms through high-throughput sequencing and iCAMP null model analysis in Co-composting of goat manure and corn straw. Three treatments were compared: 0% (CK), 5% (T1), and 10% (T2) lignite amendments (based on total solids). Results demonstrated that the 10% lignite addition significantly enhanced composting efficiency: the peak temperature increased by 0.83 °C, nitrogen loss and biotoxicity were reduced, the bacterial community structure was improved with elevated diversity and enriched keystone taxa, and the GI value was enhanced by 68.48 ± 2.99%. Notably, the relative abundances of key species, including Acinetobacter_indicus, Thermobacillus_composti, Pseudomonas_flexibilis, and Chelatococcus_thermostellatus, showed a significant positive correlation with the lignite addition gradient. The analysis of the symbiotic network centered on core microorganisms revealed that T2 showed the highest network complexity (254 links and 175 nodes), which was 46.8% and 48.3% higher than CK, respectively. Cooperative interactions dominated T2 networks, evidenced by a 13% increase in positive links for Acinetobacter (reaching 51.16%) and strengthened associations between humification-related genera (Chelatococcus and Thermobacillus links increased 1.4- and 3.2-fold, respectively). Using iCAMP null modeling, we further quantified assembly mechanisms: lignite addition increased stochastic processes (dispersal limitation increased from 47.57% in CK to 56.52% in T2) while reducing deterministic selection (homogeneous selection decreased from 25.57% to 18.47%). Acinetobacter, Chelatococcus, Ureibacillus, and Thermobacillus exhibited significant responsiveness to these ecological shifts. Collectively, 10% lignite amendment improved co-composting of goat manure and corn straw by synchronously accelerating maturity and restructuring bacterial assembly, providing a practical strategy for manure management via microbial regulation.