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Thomas C. Holt, Brian K. Maynard, and William A. Johnson

We assessed the capacity for nutrient removal of ornamental water garden plants being grown in treatment-production wetland biofilters. Plant biomass, nutrient uptake, tissue nutrient content, and production potential were compared for five popular ornamental water garden plant species: Typha latifolia L., Iris pseudacorus L., Phalaris arundinacea L. `Picta', Canna glauca L., and Colocasia esculenta (L.) Schott. Plants were grown in triplicate 0.3 m2 × 0.3 m, deep gravelbed mesocosms fed with 20N-20P-20K Peter's fertilizer (Scotts-Sierra Horticultural Products Co., Marysville, Ohio) reconstituted to 100 ppm N. After 120 days, mean species total biomass ranged from 1.4 to 5.6 kg·m -2, while producing 105 to 206 divisions per square meter. Growth for Canna and Colocasia was greatest, while Typha produced the most divisions. Mean tissue N and P concentrations ranged from 18 to 29 and 2.1 to 3.0 mg·g -1, respectively. Maximum plant accumulation of 144 g N/m 2 and 15.6 g P/m2 accounted for 70% of the N and 15% of the P supplied by fertilizer. Mean removal of total N and P ranged from 42% to 90% and 18% to 58%, respectively, and was positively correlated with plant biomass. Nutrient removal ability was ranked as Canna = Colocasia > Typha > Iris = Phalaris.

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Thomas C. Holt, Brian K. Maynard, and William A. Johnson

Degraded water quality is a growing concern across the northeast and in many cases may be linked back to agricultural operations as nonpoint sources of nitrate and phosphorous pollution. Constructed wetlands have emerged as effective, low-cost methods of water treatment that have the potential to reduce agricultural nonpoint source pollution and contribute to agricultural sustainability. However, the costs of implementing treatment wetlands as a BMP are high, with little opportunity for cost recovery. We have initiated, at a wholesale plant nursery in Rhode Island, an economical solution to treating nursery runoff that incorporates into a treatment wetland the wholesale production of native and ornamental wetland plants. Our goal is to demonstrate how nursery growers may produce a high-demand crop while addressing nonpoint source pollution on their land. Over the next few years, we will evaluate the economic impact of converting nursery production space into treatment wetland production space. We also will research the feasibility of enclosing treatment wetlands in passively heated polyhouses to facilitate the year around treatment of agricultural runoff. Information gathered from both the on-farm demonstration and research sites will be extended to farmers and other agricultural businesses or professionals through outreach programming. The theory, objectives, and construction of the demonstration treatment-production wetland will be presented.