Shifts in bacterial community associated with green manure soybean intercropping and edaphic properties in a tea plantation

Abstract

The continuous cultivation with excessive application of agrochemicals has led to the deterioration of soils. Incorporating leguminous green manure (GM) was found to improve the physicochemical and biological properties of soils. However, the influence of GM soybean intercrop-ping on the temporal distribution of bacterial communities in strongly acidic soils is less explored. In this study, a nine-month field trial of soybean intercropping was conducted in a deteriorated tea plantation. This was used to test the hypothesis that GM treatment ameliorates tea-cultivated environments through changing bacterial communities as well as edaphic properties. GM treatment was demonstrated to increase both functional and population diversity during all the months that were considered. An alteration of life strategies exhibited by bacterial communities in GM treatment was observed, which shifted from oligotrophy (Acidobacteria, Chloroflexi, and the candidate phylum WPS-2) to copiotrophy (Bacteroidetes and Proteobacteria). This also contributed to the remarkable increase in metabolic potential of bacterial communities toward all six carbon source categories. The potentially versatile organic matter decomposers and/or plant growth-promoting bacteria, such as Burkholderiaceae, Chitinophagaceae, Sphingobacteriaceae, and Sphingomonadaceae bacteria, were identified as the most effective biomarkers in GM treatment. These bacterial groups showed strong correlation with soil pH; organic matter; and available K, Ca, and Mg. The increased diversity, metabolic potential, and copiotrophic taxa provided insight into the benefits brought by soybean intercropping, with enhanced community stability, facilitated nutrient cycling, and microbe–plant interactions in the strongly acidic tea plantation.