Effects of agricultural conservation practices on oxbow lake watersheds in the Mississippi River alluvial plain

Abstract

Agricultural lands are considered to be a major source of nonpoint source pollutants such as sediment, pesticides and nutrients in the United States. Conservation practices have been tested for their effectiveness in reducing agricultural related pollutants on smaller scales, but farm watershed scale assessments of these practices are limited and few of these have evaluated the impacts on downstream ecology. Several projects focused on oxbow lake watersheds in the Mississippi River alluvial plain were designed to utilize working farms to evaluate primary pollutants in water resources and to identify conservation practices that are most effective in reducing the transport of those pollutants in surface and ground water on a watershed scale. Major findings of these studies include: (1) conservation practices reduced sediment in oxbow lakes, resulting in improved water clarity, plankton growth, and fish stocks; (2) total phosphorus in lakes decreased between 39–50% following application of conservation practices; (3) conservation tillage and cover crops reduced NO<sub>3</sub>-N losses by 73%, sediment losses by 70; and (4) riparian areas mitigated the transport of sediment in runoff and enhanced the degradation of pesticides.