Effect of organic amendments obtained from different pretreatment technologies on soil microbial community

Applying organic amendments (OAs) obtained from biological treatment technologies is a common agricultural practice to increase soil functionality and fertility. While OAs and their respective pretreatment processes have been studied extensively, it is challenging to fairly compare the effects of pretreatment processes on the properties of OAs due to the initial difference between the organic residues. Also, it is unclear to what extent OAs can affect the soil microbial community. This limits us from designing and implementing an effective pretreatment that aims to facilitate sustainable agricultural practices. fewer studies have focused on comparing the effects of OAs originating from the same bio-residues on soil biotic and abiotic properties. In this study, we tested the impact of three OAs (compost, digestate, and ferment) obtained fromapplied identical model residues for fair comparisons between the OAs (compost, digestate, and ferment) undergoing different pretreatments and their effects on the soil. Specifically, we characterized the microbial composition of OAs and investigated the prevalence of OA microbes in the soil after incorporation in a three-month microcosm experiment. We also investigated the changes in soil physicochemical properties and microbial composition after incorporation. We found that the OAs contained different microbial communities. Compost had higher bacterial but lower fungal alpha diversity than ferment and digestate. After incorporation, compost microbes were more prevalent in the soil than ferment and digestate microbes. More than 80% of bacterial ASVs and fungal OTUs from compost were detected after three months. However, the addition of compost had a minor influence on the resulting soil microbial community composition compared to the addition of ferment and digestate. Moreover, the addition of compost resulted in less soil microbial biomass than the addition of ferment and digestate. Some native soil microbes, members from Chloroflexi, Acidobacteria, and Mortierellomycota, were absent after ferment and digestate application, indicating that ferment and digestate had selection effects on soil microbes. Adding OAs also altered the abiotic properties of the soil. Adding OAs increased soil pH, particularly in the compost-amended soil. Digestate enhanced soil dissolved organic carbon (DOC) and available nutrients (e.g., ammonium and potassium). Significant correlations were found between soil microbes and these physicochemical variables, particularly soil pH, dissolved organic carbon (DOC), and available nutrients. This study provides new insights into the role of OAs obtained from different pretreatment technologies on the changes in soil microbial communities and furthers our understanding of effectively recycling organic resources for the development of sustainable soils.