Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/6/2016
Publication Date: 9/8/2016
Citation: Tyler, H.L., Locke, M.A., Moore, M.T., Steinriede Jr, R.W. 2016. Impact of conservation land management practices on soil microbial function in an agricultural watershed. Journal of Soil and Water Conservation. 71:396-403.
Interpretive Summary: Runoff from agricultural land contains excess nutrients and pesticides that can have negative impacts on downstream ecosystems. The Conservation Research Program (CRP) and vegetative buffers (VB) are two land management practices that involve taking land out of row crop (RC) production and replanting with native vegetation to reduce the impact of agriculture on the environment. Scientists in the USDA-ARS Crop Productions Systems Research Unit in Stoneville, MS and Water Quality and Ecology Research Unit in Oxford, MS conducted a field study in the Mississippi Delta to determine the long-term impact of CRP, VB, and RC land management on several soil microbial characteristics as a measure of soil health. The results of this study demonstrated the CRP and VB soils had higher activities of enzymes linked to nutrient cycling, as well as larger microbial communities compared to soil from RC lands. This study demonstrates that conservation practices are effective in improving soil health and promoting the development of soil microbial communities capable of processing agricultural pollutants deposited in VB and CRP soils from runoff. These results will provide scientists studying the efficacy of conservation practices with insight into how CRP and VB function to reduce the impact of agricultural runoff on downstream bodies of water and improve environmental quality.
Technical Abstract: The USDA Conservation Reserve Program (CRP) involves removing agricultural land from production and replanting with native vegetation for the purpose of reducing agriculture’s impact on the environment. In 2002, part of the Beasley Lake watershed in the Mississippi Delta was enrolled in CRP. In addition, areas between the lake and agricultural row crop (RC) fields were established as vegetative buffers (VB) to provide habitat for wildlife. Although the vegetative buffers were established to improve wildlife habitat, an additional ecosystem service might include serving as an impediment to runoff from adjacent upland areas. The purpose of the current study was to assess the long-term impact of CRP, VB, and RC land management practices on the soil microbial community as an indicator of soil health. Soil samples were collected at two depths (0-5 and 5-15 cm) from 12 sites within each land management (CRP, VB, and RC) area. Samples were assayed for soil enzyme activities (phosphatase, ß-glucosidase, N-acetylglucosaminidase [NAG], and fluorescein diacetate [FDA] hydrolysis), and microbial biomass. All enzyme activities were significantly higher in CRP and VB than in RC soils in the 0-5 cm depth. Microbial biomass in 0-5 cm soil was higher in CRP than in VB or RC areas. Significant correlations between microbial biomass C and the activities of phosphatase (R2=0.514; p<0.0001), glucosidase (R2=0.434; p<0.0001), and FDA (R2=0.371; p<0.0001) were observed, indicating higher extracellular enzyme activities noted in CRP and VB relative to RC soil may be partially due to a larger soil microbial community, although other factors, such as substrate availability and soil organic matter, may also play a role. The greater size and activity of microbial communities in CRP and VB indicate they are better equipped to process excess nutrients and pesticides and may be a contributing factor to the effectiveness of these conservation practices in reducing the impact of agricultural runoff on downstream bodies of water.