Microbial mechanism of crop residues addition in nitrogen leaching loss retention and soil ecosystem stability maintenance

Over fertilization is the main factor in excessive N leaching (NL) loss in greenhouse vegetable cultivation systems. Adjusting the fertilizer application rate and returning plant residues effectively reduce NL. However, the microbial mechanism of crop residues addition in NL loss retention remains largely unknown. This study established a tomato-cultivating soil column experiment with different organic fertilizer addition treatments: no organic amendment (CK), chicken manure application (CM), chicken manure +rice husk (CMR), and chicken manure +maize straw (CMM) to further explore the discrepancies in the microbial community composition and the microbial co-occurrence network structure. The results revealed that CM produced the highest yield when provided with just enough nutrients for the crop requirements. The CMR yield decreased by 26.0%, while CMM remained at the same level as CK. Although discrepancies were evident between the decomposition characteristics and nutrient release rates of the rice husk and maize straw, no differences were apparent between the mineral NL loss retention of the two materials after one growing season, exhibiting a 47.8% and 50.4% reduction compared to CM. Furthermore, crop residues addition induced rapid microbial growth, increased the microbial community richness, and caused lignocellulose degraders accumulation, with fewer operational taxonomic units (OTUs) associated with the nitrification process. The CMM treatment produced a more robust and complex microbial co-occurrence network that was absent in the CM treatment. The results implied an alleviating effect of the straw amendment on mineral NL loss and emphasized the importance of readily available C sources in stabilizing an ecosystem.