No-tillage systems promote bacterial photosynthetic gene expression in low carbon, semi-arid surface soils.

Managing soils in semi-arid agricultural croplands generally focuses on reducing wind erosion, increasing fertility, and storing carbon. Thus, converting conventionally tilled systems to no-tillage and cover-cropped systems are often the first steps towards a conservation management approach across the growing area of semi-arid croplands. From a soil biological perspective, introducing cover crops to semi-arid soils has been shown to alter microbial community structure, which may lead to changes in the biogeochemical pathways expressed in these soils. In this study, we examined the impact of single-species wheat cover cropping and no-tillage on microbial gene expression after 4 and 5 years of implementation. We sequenced the metatranscriptomes of three production systems with varying levels of conservation management: conventional tillage winter fallow, no-tillage winter fallow, and no-tillage with a winter wheat cover crop. Removing tillage was the biggest factor altering microbial gene expression in this study, specifically resulting in upregulation of several photosystem-associated functions. These functions were taxonomically linked to organisms that make up the early stages of biological soil crusts, which may introduce additional benefits to these semi-arid agricultural systems beyond a reduction in wind erosion. Implementing a cover crop did not clearly alter gene expression beyond the effect of tillage removal; however, it did indicate a potential to reduce fungal disease incidence in 1 year of the study. These alterations of microbial activities and selection for potentially beneficial functions should be considered and further studied to aid in maintaining sustainable croplands for our changing climate.IMPORTANCEEliminating tillage from semi-arid agricultural soils has the potential to significantly alter the activities of the soil bacterial community compared with conventionally tilled soils. A major driver of this change was the activities of biological soil crust forming organisms that can provide several environmental benefits to the soil ecosystem beyond the typically associated benefits of conservation management. Furthermore, this study revealed that the implementation of a cover crop regime on no-tillage soils does not confer a major change in the function of the organisms present. Overall, the study reported here reveals that soil management practices aimed at reducing wind erosion and improving sustainability will positively impact the function of the microbial community and suggests that future investigations into the consequences of these functional changes may provide valuable services to these agricultural ecosystems.