UNDERSTANDING AND PREDICTING THE IMPACT OF AGRICULTURE ON THE ENVIRONMENTAL INTEGRITY OF MANAGED WATERSHEDS
Location: Water Quality and Ecology Research
Title: Influence of three aquatic macrophytes on mitigation of nitrogen species from agricultural runoff
Submitted to: Water, Air, and Soil Pollution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 31, 2012
Publication Date: June 9, 2012
Citation: Tyler, H.L., Moore, M.T., Locke, M.A. 2012. Influence of three aquatic macrophytes on mitigation of nitrogen species from agricultural runoff. Water, Air, and Soil Pollution. 223(6):3227-3236.
Interpretive Summary: Hypoxia in the Gulf of Mexico has been a growing concern for decades. Best management practices are needed to help reduce the potential harmful effects of nutrients in agricultural runoff before they reach receiving systems such as rivers and lakes, and eventually, the Gulf. Several management practices rely on vegetation (constructed wetlands, drainage ditches, riparian zones, etc.) to help mitigate nutrients from the runoff water. This study examined three plant species common to wetland and ditch habitats and found they were able to reduce the amount of nitrate and ammonium in runoff water following a simulated storm event. This type of research is crucial in developing our understanding of ways to better design vegetated system that serve as nutrient filters for agricultural runoff.
Agricultural runoff containing nitrogen fertilizer is a major contributor to eutrophication in aquatic systems. One method of lowering amounts of nitrogen entering rivers or lakes is the transport of runoff through vegetated drainage ditches. Drainage ditch vegetation can enhance the mitigation of nutrients from runoff; however, the efficiency of nitrogen removal can vary between plant species. The efficiency of three aquatic macrophytes, cutgrass (Leersia oryzoides), cattail (Typha latifolia), and bur-reed (Sparganium americanum), to mitigate dissolved and total nitrogen from water was investigated. Replicate mesocosms of each plant species were exposed to flowing water enriched with ammonium and nitrate for 6 h, allowed to sit 42 h, and then flushed with non-enriched water for an additional 6 h to simulate a second storm event. After termination of the final simulated runoff, all vegetated treatments lowered total nitrogen loads exiting mesocosms by greater than 50%, significantly more than unvegetated controls, which only lowered concentrations by 26.9% (p = 0.0023). L. oryzoides and T. latifolia were more efficient at lowering dissolved nitrogen, decreasing ammonium by 42±9 and 59±4 % and nitrate by 67±6 and 64±7%, respectively. All treatments decreased ammonium and nitrate concentrations within mesocosms by more than 86% after one week. However, T. latifolia and L. oryzoides acted more rapidly, lowering concentrations by greater than 98% within 48 hr. By determining the nitrogen mitigation efficiency of different vegetative species, plant communities in agricultural drainage ditches can be managed to significantly increase their remediation potential.