Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 9/1/2007
Publication Date: 11/5/2007
Citation: Armstrong, S., Smith, D.R. 2007. The Effect of Time after Ditch Dredging on Phosphorus Transport. American Society of Agronomy Annual Meeting Abstracts. November 4-8, 2007, New Orleans, LA. 2007 CDROM. Interpretive Summary:
Technical Abstract: Ditch dredging is a critical management practice for agricultural catchments in the Midwestern region of the United States that enhances the removal of water from agricultural fields. Recently, short-term ditch dredge studies have shown that the newly exposed sediments following dredging has a less reactive surface and release a greater concentration of P to the overlying water column that could lead to water impairment. The objective of this study was to determine the effect of time after dredging on P desorption. Sediment samples were collected over a 4 month period from un-dredged and dredged ditches in Northwest Ohio. The sediment samples from each date were analyzed for particle size distribution, labile extractable P, % C and equilibrium P concentration (EPCo), before being placed into a stream simulator, where P adsorption and desorption experiments were conducted. The adsorption phase was performed by circulating inoculated (0.55 mM P) stream water for 144 hr, followed by 24 hr. desorption phase with clean distilled water. After 45 days the P adsorption for both the dredged and un-dredged sediments decreased with time and the P desorption properties of the dredged ditch sediments remain constant. However, net P desorption for the un-dredged sediments increased from 0.2 mg P L-1 to 0.5 mg P L-1 within a time period of 45 days. Results from this study provide conservation managers with the long-term effects of ditch dredging on soluble P transport in drainage ditches.