Soil bacterial communities benefit from long-term cover crop mixtures

Abstract

Understanding the long-term impacts of cover cropping on soil health indicators is vital for developing sustainable farming practices. The aim of the current study was to investigate the impacts of long-term mixed cover crops practice in a no-till system on soil bacterial community abundance and diversity using 16S rRNA sequencing. We compared three cover crop practices againist a no-cover crop control (NCC): cereal rye only (Rye), a mixture of cereal rye and hairy vetch (RyeHV), and a mixture of cereal rye, hairy vetch, crimson clover, and Australian winter pea (Mixed). These treatments were arranged in a completely randomized block design with four replications. The abundance of soil bacteria was lower in the Rye treatment compared to the Mixed and RyeHV treatments, possibly due to the uniform supply of resources (exudates) and the limited root structure, rather than due to the increased soil bulk density or reduced organic carbon. This reduction was observed in the total operational taxonomic units and the dominant taxa groups, including Actinobacteria, Proteobacteria, Firmicutes, and Acidobacteria. Non-metric Multidimensional Scaling analysis, using Bray-Curtis dissimilarity, revealed distinct bacterial community structure between the Rye and the rest of treatments, but with a potential overlap of that of NCC with all the cover crop treatments. In conclusion, our study revealed that unlike mixed species cover crops, a single species cover crops may compete for resources with soil bacterial community, leading to a reduced abundance of soil bacteria. Moreover, possible positive impact of cover cropping on soil physicochemical properties may not always have relationships with soil bacterial alpha diversity. Future research should explore attributes of mixed cover crops that may be crucial in driving microbial community structure.