Submitted to: Environmental Pollution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/22/2004
Publication Date: 12/1/2004
Citation: Bouldin, J.L., Farris, J.L., Moore, M.T., Cooper, C.M. 2004. Vegetative and structural characteristics of agricultural drainage in the Mississippi Delta landscape. Environmental Pollution. 132(3):403-411. Interpretive Summary: Ditches surround farmland in order to help move water off the crops during a storm event. These ditches eventually empty into a larger body of water, such as a river, lake, or stream. A recently discovered benefit of these drainage ditches is that they are capable of improving the quality of the runoff water before it enters lakes, rivers, and streams. One objective of this research was to characterize several different aspects (water depth, bank width, surrounding land use, etc.) of a variety of sizes of drainage ditches and determine their effects upon water quality. A second objective of this research was to characterize the types of plants that live in the different types of drainage ditches within the Mississippi Delta region.
Technical Abstract: Agricultural drainage ditches are an important aspect of the Mississippi Alluvial Delta landscape and vary from small edge-of-field waterways to sizeable drainage systems. Attributes of these ditches vary with size, location and maintenance and are important in determining the functionality that aids in mitigation of contaminants from agricultural fields. The goal of this study was to better understand how vegetative characteristics affect water quality in conveyance structures in the context of ditch class and surrounding land use. A total of 36 agricultural ditches in the Mississippi Delta were characterized by spoil size, presence of riparian buffer strips, hydroperiod, water depth, surrounding land use and vegetative cover, concurrent with associated aqueous physiochemical parameters. Vegetation was assessed quantitatively, obtaining stem count in a subsample of sites, using random quadrate method. Physical features varied with ditch size and vegetative diversity was higher in larger size structures. Four vegetative types were ubiquitous among sites with Polygonum sp. being the dominant bed vegetation. Macrophytes varied from aquatic to upland species, and included Leersia and upland grasses in all drainage size classes. Percent cover of bed and bank varied from 0-100% and 70-100%, respectively. Highest nutrient values were measured in sites with no buffer strips. These conveyance structures and surrounding buffer zones serve to mitigate contaminants often found in runoff that may include excess nutrients, suspended solids and pesticides.