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ARS Home » Southeast Area » Oxford, Mississippi » National Sedimentation Laboratory » Water Quality and Ecology Research » Research » Publications at this Location » Publication #383750

Research Project: Strategic Investigations to Improve Water Quality and Ecosystem Sustainability in Agricultural Landscapes

Location: Water Quality and Ecology Research

Title: Vegetation and Residence Time Interact to Influence Metabolism and Net Nutrient Uptake in Experimental Agricultural Drainage Systems

item NIFONG, RACHEL - US Department Of Agriculture (USDA)
item Taylor, Jason

Submitted to: Water
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/13/2021
Publication Date: 5/19/2021
Citation: Nifong, R.L., Taylor, J.M. 2021. Vegetation and residence time interact to influence metabolism and nutrient assimilation in experimental agricultural drainage systems. Water.

Interpretive Summary: Excess nutrients from wastewater and agricultural runoff threaten freshwater and marine ecosystems around the world. In response to this threat, agricultural and ecological researchers are expending considerable efforts to develop and implement best management practices that reduce nutrient impacts to critical water resources. One approach is allowing vegetation to grow and increasing hydraulic residence in agricultural ditches to increase potential environmental benefits, including nutrient removal. Here we tested the combined effects of vegetation and increasing residence time on nutrient uptake in experimental agricultural ditches. We found higher metabolic activity of bacteria, algae and plants in vegetated ditches which resulted in higher nutrient removal from water flowing through ditches. In short, this study emphasizes the utility of vegetation in nutrient processing in drainage ditches. Our results provide strong support for establishing vegetation in agricultural drainage ditches to reduce nutrient loss to downstream ecosystems impacted by excess nutrient runoff, including the Gulf of Mexico, and should be of interest to farmers, regulatory agencies, and landowners.

Technical Abstract: Agricultural drainage networks within the Lower Mississippi River Basin (LMRB) have potential to attenuate nutrient loading to downstream aquatic ecosystems through best management practices. Nutrient uptake (Nitrogen, Phosphorus), gross primary production (GPP), ecosystem respiration (ER), and denitrification rates were estimated using a combination of sensor measurements and hourly discrete samples for dissolved nutrients and gases at three hydraulic residence times (2, 4, and 6 h) in 3 vegetated and 3 unvegetated ditches. We also measured vegetation and soil nutrient content. GPP and ER were significantly higher in vegetated drainages and increasing hydraulic residence time increased respiration rates. Shorter hydraulic residence times were associated with increased uptake rates for both N and P, and vegetation increased N uptake rates in all hydraulic residence time (HRT) treatments. Vegetation and sediment assimilated N and P over the course of the experiment. Overall, our experimental results demonstrate the strong role of emergent vegetation in nutrient retention and removal processes in agricultural drainage ditch networks.