Monday, November 5, 2007
19-7
The Short Term Effects of Ditch Dredging to Nutrient Saturation onto Ditch Bed Materials.
Eric Miller, Purdue University-Agronomy Club, 4462 S 100 W, Star City, IN 46985
In the Midwestern United States, drainage ditches are an essential part of our landscape to ensure agriculture productivity. Sediment buildup reduces the flow rate of ditches and thus field tile lines, it then becomes necessary to dredge drainage ditches occasionally to optimize removal of water from farm fields. Ditch dredging has a direct effect on the nutrient concentrations, which are dissolved in the water column or are adsorbed on the sediment colloids. Ditch bed materials were collected from a control ditch, a second ditch prior to dredging (Pre-Dredge), and the second ditch after dredging (Post Dredge). These ditch bed materials were placed in a fluvarium, and contaminated water (13.6 mg/L P and 14.8 mg/L NH4–N) was used to study nutrient adsorption/ transformations by the sediments. After 143 hours, the contaminated water was replaced with contaminant free water. Concentrations of P were reduced the most in the control ditch and in the Pre-Dredged ditch; these concentrations were nearly reduced to 0 mg/L. The Post-Dredged ditch did not reduce the P concentrations as much and did not reach as low of level at hour 143. The immediate effects of ditch dredging on nutrient adsorbed by ditch bed sediments are that ditch dredging decreases the P buffering capacity of the ditch bed sediments, resulting in poorer water quality.