Effects of Varying Suites of Agriculture Conservation Practices on Water Quality in the Mississippi Delta

Author(s): Baker, B.; Prince Czarnecki, J.; Omer, A.; Aldridge, C.; Kroger, R.; Prevost, J.

Increasing concern regarding environmental degradation and annual hypoxic zones has led to the need for mitigation of nutrient laden runoff from inland landscapes. An annual occurrence of a hypoxic zone in the Gulf of Mexico has led to the development and implementation of nutrient reduction strategies at the state level throughout the Mississippi River Basin (MRB). With federal, state, and private financial and technical assisstance, landowners have implemented best management practices (BMPs) to reduce nutrient and sediment loading; however, the effectiveness of these BMPs to improve water quality, alone or utilized together, has not been widely documented. This research includes a field-scale, paired watershed approach in two watersheds in the Mississippi Alluvial Valley to test for differences in sed¬iment and nutrient runoff concentrations between four management systems. Baseflow and stormflow samples were collected from 2011 to 2015 and analyzed for nutrient and sediment concentrations. Median baseflow concentrations across all sites were 52 mg L–1 for total suspended solids (TSS), 0.38 mg L–1 for total phosphorus (TP), 0.09 mg L–1 for nitrate-nitrite (NO3-NO2-), and 0.81 mg L–1 for ammonium (NH4+). Median sediment and nutrient concentrations from stormflow samples across all sites within the study were greater than baseflow concentrations, where median stormflow concentrations were 985 mg L–1 for TSS, 1.21 mg L–1 for TP, 0.32 mg L–1 for NO3-NO2, and 1.04 mg L–1 for NH4+. Results showed no strong improvements in water quality from agricultural landscapes where suites of BMPs had been implemented. Rather, the data presented variability in runoff concentrations indicative of strong influences from environmental and management vari¬ables. Study outcomes highlight opportunities to better capture nutrient dynamics at the field scale through adaptive management of BMPs and the importance of in-field practices for improved water quality to improve nonpoint source pollution reduction.

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