Comparative nutrient remediation by monoculture and mixed species plantings within floating treatment wetlands

Authors: GARCIA CHANCE, LAUREN - Clemson University; MAJSZTRIK, JOHN - Clemson University; BRIDGES, WILLIAM - Clemson University; WILLIS, ASHLEY - Clemson University; Albano, Joseph; WHITE, SARA - Clemson University

Submitted to: Environmental Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/23/2020
Publication Date: 6/23/2020
Citation: Garcia Chance, L., Majsztrik, J., Bridges, W., Willis, A.S., Albano, J.P., White, S. 2020. Comparative nutrient remediation by monoculture and mixed species plantings within floating treatment wetlands. Environmental Science and Technology. 54(14):8710-8718. https://doi.org/10.1021/acs.est.0c00198.
DOI: https://doi.org/10.1021/acs.est.0c00198

Interpretive Summary: Irrigation return water from container plant nurseries often contains elevated levels of nitrogen (N) and phosphorus (P). Floating treatment wetlands (FTWs) are one solution for removing nutrients from irrigation return flow. This study assessed how FTW planting strategy (monoculture vs mixed planting) influenced removal of N and P. Experimental treatments were a control (open water); monoculture plantings (Iris ensata ‘Rising Sun’, Canna ×generalis ‘Firebird’, Agrostis alba, Carex stricta, or Panicum virgatum); or mixed plantings [2 mixtures: partial (monocots only) or a complete mixture of all plants]. For FTWs established in all treatments (except control), N and P removal from solution was additive, with a similar mass of N and P removed. However, when assessing nutrient uptake within plant tissues in FTWs, Panicum virgatum performed better (absorbed more N) within mixtures, a possible synergistic effect, while Iris ensata ‘Rising Sun’ performed poorly (fixed less N) within the complete mixture, a possible antagonist effect. Nutrient assimilation within plant tissues did not correlate with overall remediation performance for monocultures or mixtures, as tissue accumulation varied by nutrient and mixture.

Technical Abstract: Irrigation return water from container plant nurseries often contains elevated levels of nitrogen (N) and phosphorus (P). Floating treatment wetlands (FTWs) are one solution for removing nutrients from irrigation return flow. This study assessed how FTW planting strategy (monoculture vs mixed planting) influenced removal of N and P. Tanks containing FTWs received water with ~22.3 N and 3.12 mg·L–1 P water-soluble fertilizer every 7 days for two, 8-week experiments. Experimental treatments were a control (open water); monoculture plantings (Iris ensata ‘Rising Sun’, Canna ×generalis ‘Firebird’, Agrostis alba, Carex stricta, or Panicum virgatum); or mixed plantings [2 mixtures: partial (monocots only) or a complete mixture of all plants]. For FTWs established in all treatments (except control), N and P removal from solution was additive, with a similar mass of N and P removed. However, when assessing nutrient uptake within plant tissues in FTWs, Panicum virgatum performed better (absorbed more N) within mixtures, a possible synergistic effect, while Iris ensata ‘Rising Sun’ performed poorly (fixed less N) within the complete mixture, a possible antagonist effect. Nutrient assimilation within plant tissues did not correlate with overall remediation performance for monocultures or mixtures, as tissue accumulation varied by nutrient and mixture.