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Are microbial communities indicators of soil health in a dryland wheat cropping system?

Schlatter, Daniel C. Hansen, Jeremy Carlson, Bryan Leslie, Ian N. Huggins, David R. Paulitz, Timothy C.. 2022.

Abstract

Soil health is an increasingly important concept that provides aspirational targets for agricultural management. Due in part to the incredible diversity of soil microbial communities, however, the biological components of soil health remain poorly understood. In the last decade the refinement of high-throughput DNA sequencing approaches for examining soil microbial communities has led to sequence-variant resolution insights into their diversity. In this work we employ high-throughput sequencing of bacterial (16S rRNA genes) and fungal (internal transcribed spacer [ITS]) regions to evaluate soil microbial communities in relation to other soil chemical parameters, biological soil health tests, and crop yields in fields under long-term reduced tillage (business-as-usual) and no tillage (aspirational) management at two soil depths. We found that tillage systems and soil depth were crucial determinants of microbial community composition and diversity in conjunction with soil chemical measures. Moreover, although some measures of biological soil health (CO2-burst, Haney Soil Health Score) did not differentiate fields under reduced tillage and no-till systems, amplicon sequencing revealed clear differences in microbial communities between management regimes. The relative abundances of many microbial taxa were significantly related to soil chemical variables and crop yields. Fungal communities showed stronger correlations with yield than bacterial communities at both depth increments. Fungi from the families Sordariaceae, Hydnodontaceae, Hypocreaceae, and Clavicipitaceae were positively correlated with yield, especially in the upper soil depth, while Glomeraceae and Phaeosphaeriaceae were negatively correlated. Many of these correlations were also seen in the subsequent winter wheat and chickpea crops, and some correlations could be detected in the 20-year previous yield history of the no-tillage farm. Among the bacteria, only Microbaceriaceae and Xanthomonadaceae were positively correlated, but Caulobacteriaceae, Flavobacteriaceae, Sphingobacteriaceae, Chitinophagaceae were more abundant in lower yielding locations. This may reflect the strong plant selection in the rhizosphere for these bacterial groups in stressed plants. There were no significant differences, however, between microbial diversity and management practices or significant correlations with crop yields. These results suggest that some specific groups of microbial taxa are responsive to tillage systems, exhibit positive relationships with grain yields, and may be useful indicators of soil health.

Key Words

Microbiome Soil quality No-till Soil depth Bacteria Fungi