Assessment of Soil Microbial Communities after Long-Term Implementation of Land Conservation Practices.

Conservation management practices have been introduced as a way to restore soil health in land used for agricultural production and limit the impact of agriculture on downstream ecosystems. In 2003, part of the Beasley Lake watershed in the Mississippi Delta was enrolled in the Conservation Reserve Program (CRP), where cotton and soybean fields were removed from production and replanted with native vegetation. Three years later, additional areas in the watershed were established as vegetative buffers (VB) adjacent to row cropped (RC) fields to provide wildlife habitat. The purpose of the current study was to evaluate how these conservation practices influence soil microbial communities. Samples were collected from 12 sites in each region of the watershed (RC, CRP, and VB) at two depths (0-5 and 5-15 cm). Several measured parameters indicated that microbial communities are larger and more active in CRP and VB soils. 16S rRNA gene sequencing revealed microbial community composition differed significantly by land use and depth. CRP soils contained significantly more Rhizobiales (N-fixing plant symbionts), while RC soils contained more Xanthomonadales (bacterial order known to contain plant pathogens). Fewer differences in community composition were observed between depths in RC samples, likely due to tillage of the soil for crop cultivation. This study demonstrates how these conservation practices can influence microbial communities and enhance soil health.