UNDERSTANDING AND PREDICTING THE IMPACT OF AGRICULTURE ON THE ENVIRONMENTAL INTEGRITY OF MANAGED WATERSHEDS
Location: Water Quality and Ecology Research
Title: Low-grade weirs in agricultural drainage ditches: An experimental approach to decreasing nitrate-N
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 1, 2011
Publication Date: July 1, 2011
Citation: Littlejohn, K.A., Kroger, R., Moore, M.T., Farris, J.L. 2011. Low-grade weirs in agricultural drainage ditches: An experimental approach to decreasing nitrate-N. Abstracts of the Joint Meeting of the Society of Wetland Scientists, Wetpol and Wetland Biogeochemistry Symposium, Prague, Czech Republic, 3-8 July, 2011. p. 417.
Interpretive Summary: Abstract Only - Interpretative Summary not required.
Agricultural runoff carries high nutrient loads to receiving waters contributing to eutrophication. Managed wetlands can be used in integrated management efforts to intercept nutrients before they enter downstream aquatic systems, but detailed information regarding sorption and desorption of P by wetland sediments during typical inundation cycles is lacking. This study seeks to quantify and elucidate how inundation of field managed wetland sediments affects bioavailability of P, and contributions of P to downstream systems. A managed wetland cell in Tunica County, Mississippi was subjected to a simulated agricultural runoff event, and was monitored for bioavailable phosphorus (water extractable P = Pw and Fe-, Al-P) of wetland sediments and water level during the runoff event and for 130 d afterward. Inundation varied longitudinally within the wetland, with data supporting significant temporal relationships between inundation and Pw desorption. Pw concentrations were significantly higher at the site which exhibited variable hydroperiod (100 m) as compared to sites under consistent inundation. This suggests that sites that are inundated for longer periods of time desorb less Pw immediately to the environment, than sites that have periodic or ephemeral inundation. Feox and NaOH-P concentrations were significantly higher at the least inundated site as compared to all other sites (F = 5.43; p = 0.001) irrespective of time. Evidently, it is hypothesized that increased hydraulic residence time can decrease the bioavailability of phosphorus in wetland sediments receiving agricultural runoff. This finding suggests that the restoration of wetlands in the Mid-South may be hydrologically managed to improve P retention.