Submitted to: Book Chapter
Publication Type: Book / chapter
Publication Acceptance Date: 1/31/2009
Publication Date: 12/1/2009
Citation: Kroger, R., Holland, M.M., Moore, M.T., Cooper, C.M. 2009. Seasonal Patterns of Nitrogen and Phosphorus Losses in Agricultural Drainage Ditches in Northern Mississippi. In: Hudspeth, Ch. A. and Reeve, T. E. (Eds.). Agricultural Runoff, Coastal Engineering and Flooding. Nova Science Publishers, Inc. pp. 279-289. Interpretive Summary: Drainage from agricultural lands contains many pollutants, including excess nutrients. A two-year study of farm ditches were sampled for baseflow and stormflow nitrogen and phosphorus concentrations. High nitrogen concentrations were seen during baseflow sampling, while high phosphorus concentrations were noted during stormflow sampling. Information on how nutrients are transported from fields through ditches will aid farmers and other conservationists in adequately designing strategies to mitigate potential downstream effects of excessive nutrient runoff.
Technical Abstract: Drainage ditches convey nutrient laden waters from agricultural landscapes to receiving waters. Surface drainage ditches are landscape features that have been overlooked for non-point source pollution mitigation of receiving waters. The objective of this study was to determine the nitrogen and phosphorus concentrations of agricultural drainage ditches in baseflow and stormflow under natural rainfall conditions from no-till cotton in northern Mississippi. Two farm ditches were compared against two control ditches for two years. Sites were sampled monthly for baseflow, rainfall generated storm flow, and overland surface runoff. Baseflow is defined as flow independent of a rainfall event, while stormflows are event driven which generate elevated water levels within the drainage ditch and overland surface runoff. Nitrogen and phosphorus concentrations were highest after fertilization events in 2004 and 2005 and subsequently decreased in concentration throughout the rest of the year. High nitrate-N concentrations were associated with baseflow and subsurface processes, while high total orthophosphate and particulate phosphorus concentrations were associated with surface processes of overland surface runoff and stormflows. Understanding specific nutrient biogeochemistry and the interactions with hydrological flows highlight nutrient loss pathways from agricultural landscapes. Information on nutrient loss and hydrology can be used to quantify nutrient loss loads and aid in determining the current mitigation capacities of agricultural drainage ditches.