Submitted to: Society of Wetland Scientists
Publication Type: Abstract only
Publication Acceptance Date: 7/1/2006
Publication Date: 7/20/2006
Citation: Kroger, R., Holland, M.M., Moore, M.T., Cooper, C.M. 2006. Nutrient flux in agricultural drainage ditches: when and how do nutrients move?. Society of Wetland Scientists 27th International Conference, Cairns, Australia. p 72. Interpretive Summary: Abstract only. Interpretive summary not required.
Technical Abstract: Agricultural activities play a major role as non-point sources of nutrients such as nitrogen and phosphorus. Drainage ditches are integral parts of the agricultural landscape, and act as major conduits for nutrients such as N and P from agricultural lands to receiving waters. However, very little research has gone into investigating the utilization of agricultural landscape features for mitigation of nutrients associated with drainage and storm water runoff. The reason is primarily a lack of data on nutrient flux within drainage ditches. We undertook a two year study of two drainage ditches to monitor nutrient flux on both spatial and temporal gradients. These data were compared against two controls. Water samples were collected monthly to establish baseflow ditch nutrient loads, and collected with every storm event that generated surface runoff and elevated water levels within the ditch. Sediment samples were collected monthly to determine assimilation rates of nutrients. Results for nitrogen species suggest that TIN levels spike and reach maximum levels post fertilization (6.28 mg N/L + 3.64), but also reach high levels in winter (18.7 mg N/L + 2.98), when vegetative senescence provides a large input of inorganic nitrogen into the system. Similar patterns emerge with the runoff and storm data. Phosphorus concentrations were highest with storm (4.35 mg P/L + 0.39) and runoff events (3.75 mg P/L + 0.023) post fertilizer application, which was expected as the majority of TOP is particulate bound. Phosphorus loads were greatest per storm event in winter as the majority of rainfall occurred over this period. Hydrological variability plays an important role in the movement of phosphorus and nitrogen species from the farm into the drainage ditches and its effect on downstream environments.