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Robert F. Polomski, Milton D. Taylor, Sarah A. White, Ted Whitwell, Stephen J. Klaine and William C. Bridges Jr.

Commercial nurseries use large amounts of water and nutrients during production cycles. Runoff contaminated with N and P can adversely impact surface and groundwater quality. A 3-year monitoring study of nutrient mitigation by a constructed wetland at a container nursery found nitrogen removal was highly efficient. However, orthophosphate-P removal was highly variable. Partial removal occurred during some months, but net export also occurred. P levels in wetland discharge—between 0.84 and 2.75 ppm—were well above the generally accepted level for preventing downstream eutrophication. Therefore, identifying landscape plants that remediate nutrients, especially P, could be useful in improving constructed wetlands. A 2003 greenhouse study screened commercially available landscape plants for their phytoremediation potential. Among the 17 taxa and 19 cultivars examined were woody shrubs, e.g., Cornusamomum, Myricacerifera`Emperor', and Salix integra `Hakura Nishiki'; herbaceous semiaquatics, e.g., Canna(two cultivars), Colocasia esculenta `Illustris', Rhyncospora colorata, Iris`Full Eclipse', Pontederia cordata `Singapore Pink', and Thalia geniculata `Red Stem'; and floating aquatics, e.g., Myriophyllum aquaticum, Eichhornia crassipes, and Pistia stratiotes. Plants were grown in pea gravel media and kept saturated with one of five concentrations of Hoagland's. Herbaceous and woody plants were harvested after 8 and 13 weeks, respectively. Experiments were replicated twice for each cultivar. The nutrient uptake efficiency was determined for each taxon from the total amount of N and P applied and the biomass dry weight and N and P content.

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Robert F. Polomski, Douglas G. Bielenberg, Ted Whitwell, Milton D. Taylor, William C. Bridges and Stephen J. Klaine

Intensive production of container-grown nursery and greenhouse crops in soilless substrate may result in significant leaching of nutrients and pesticides. The resulting runoff can escape from production areas and negatively impact surface and ground water. Constructed wetlands (CWs) have been shown to be a simple, low-technology method for treating agricultural, industrial, and municipal wastewater. We investigated the nitrogen (N) and phosphorus (P) removal potential by a vegetated, laboratory-scale subsurface flow (SSF) CW system. Over an 8-week period, five commercially available aquatic garden plants received a range of N and P (0.39 to 36.81 mg·L−1 N and 0.07 to 6.77 mg·L−1 P) that spanned the rates detected in nursery runoff. Whole plant dry weight was positively correlated with N and P supplied. Highest N and P recovery rates were exhibited by Thalia geniculata f. rheumoides Shuey and Oenenathe javanica (Blume) DC. ‘Flamingo’, Phyla lanceolata (Michx.) Greene also had high P recovery rates. The potential exists for using SSF CWs to concomitantly produce aquatic garden plants and attenuate nutrients in a sustainable nursery enterprise.

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Robert F. Polomski, Douglas G. Bielenberg, Ted Whitwell, Milton D. Taylor, William C. Bridges and Stephen J. Klaine

Commercial nurseries use large amounts of water and nutrients to produce container-grown plants. The large volume of runoff containing nitrogen (N) and phosphorus (P) that leaves nurseries can contaminate surface and groundwater. Subsurface flow-constructed wetlands have been shown to effectively treat agricultural, industrial, and residential wastewater and to be well-suited for growers with limited production space. We investigated the possibility of using commercially available aquatic garden plants in subsurface-constructed wetlands to remove nutrients in a laboratory scale, gravel-based system. Seven popular aquatic garden plants received N and P from Hoagland's nutrient solution every 2 days for 8 weeks. These rates (0.39 to 36.81 mg·L−1 of N and 0.07 to 6.77 mg·L−1 P, respectively) encompassed low to high rates of nutrients found at various points between the discharge and inflow points of other constructed wetland systems currently in use at commercial nurseries. Plant biomass, nutrient recovery, and tissue nutrient concentration and content were measured. Whole plant dry weight positively correlated with total N and P supplied. Louisiana Iris hybrid ‘Full Eclipse’, Canna × generalis Bailey (pro sp.) ‘Bengal Tiger’, Canna × generalis Bailey (pro sp.) ‘Yellow King Humbert’, Colocasia esculenta (L.) Schott ‘Illustris', Peltandra virginica (L.) Schott, and Pontederia cordata L. ‘Singapore Pink’ had the greatest N recovery rates. The P recovery rates were similar for the cannas, Colocasia esculenta ‘Illustris’, Louisiana Iris ‘Full Eclipse’, Pe. virginica, and Po. cordata ‘Singapore Pink’. The potential exists for creating a sustainable nursery and greenhouse production system that incorporates a subsurface-constructed wetland planted with marketable horticultural crops that provide remediation and revenue.