Effect of composting on bacterial communities in poultry litter generated using conventional and organic production...

Poultry production generates substantial quantities of poultry litter, which can be applied to agricultural soils as organic fertilizer. Although this production system is sustainable, it can increase the microbial numbers and change ecological interactions and trophic networks in the soil. This study evaluated the composition, diversity, and structure of bacterial communities in poultry litter generated using conventional and organic production systems and subsequently composted under identical conditions for 125 days. Samples were collected before and after composting. Measurements included temperature, pH, electrical conductivity, and CO₂ and NH₃ emissions before and after composting. Total DNA was extracted, and the V3-V4 region of the 16S rRNA gene was sequenced using amplicon sequencing. The poultry litter reached temperatures around 65°C (±2°C) for 3 consecutive days, as established by Brazilian regulations for compost sanitization. The most abundant bacterial classes were Gammaproteobacteria and Alphaproteobacteria, representing 24.7% and 20.6% of the amplicon sequence variants, respectively. Among these groups, the orders Pseudomonales and Rhizobiales predominated. The order Enterobacterales was not detected in any of the poultry litter, before or after composting. Less abundant classes, such as Deltaproteobacteria, Bacilli, and Actinobacteria, showed reduced taxonomic diversity in both poultry litter after composting. Greater complexity and interconnection within the communities in both poultry litters were observed after composting. The bacterial community composition, diversity, and structure were influenced by both composting and the type of production system used. The impact of these remaining microorganisms on soil warrants further investigation because they can cause structural and functional changes in soil environments.