Bacteria in (vermi)composted organic wastes mostly survive when applied to an arable soil cultivated with wheat...

Composting and vermicomposting are an environmentally friendly way to reduce pathogens in organic wastes and generate a valuable product that provides nutrients for crops. However, how the bacterial community structure changes during these different processes and if the bacteria applied with the (vermi)composted products survive in an arable cultivated soil is still largely unknown. In this study, we monitored how the bacterial community structure changed during conditioning, composting with and without Eisenia fetida, and when the end-product was applied to arable soil cultivated with wheat Triticum sp. L. The organic wastes used were biosolid, cow manure, and a mixture of both. Large changes occurred in the relative abundance of some of the most abundant bacterial genera during conditioning, but the changes were much smaller during composting or vermicomposting. The bacterial community structure was significantly different in the organic wastes during conditioning and (vermi)composting but adding E. fetida had no significant effect on it. Changes in the relative abundance of the bacterial groups in the (vermi)composted waste applied to the arable soil cultivated with wheat were small, suggesting that most survived even after 140 days. As such, applying (vermi)composted organic wastes not only adds nutrients to a crop but also contributes to the survival of plant growth-promoting bacteria found in the (vermi)compost. However, putative human pathogens found in the biosolid also survived in the arable soil, and their relative abundance remained high but mixing the biosolid with cow manure reduced that risk. It was found that applying (vermi)composted organic wastes to an arable soil not only provides plant nutrients and adds bacteria with plant growth-promoting capacities, but some putative pathogens also survived.