JOBNAME: horts 43#3 2008 PAGE: 1 OUTPUT: April 23 09:13:23 2008 tsp/horts/163067/02647 HORTSCIENCE 43(3):868–874. 2008. amount of pollutant that a water body can receive from point and nonpoint sources and still maintain its designated use and value Differential Nitrogen and Phosphorus (e.g., drinking water, fish and wildlife habitat, recreation, and so on). The Clean Water Act Recovery by Five Aquatic Garden (U.S. EPA, 1994) lists nitrogen (N) and phosphorus (P) as potential pollutants of Species in Laboratory-scale impaired water bodies. Offsite movement of – nitrate–nitrogen (NO3 ) and soluble reactive – 2– 3– phosphate (H2PO4 , HPO4 , and PO4 ) from Subsurface-constructed Wetlands nursery and greenhouse operations may lead Robert F. Polomski1,6, Douglas G. Bielenberg3, and Ted Whitwell5 to excessive algal and aquatic plant growth Department of Horticulture, Clemson University, 254 Poole Agricultural in surface waters, resulting in accelerated eutrophication. In general, freshwater systems Center, Clemson, SC 29634-0319 are P-limited and more prone to P inputs, Milton D. Taylor2 whereas N often limits primary production in estuarine and marine environments InsectiGen, Inc., 425 River Road, Athens, GA 30602 (Carpenter et al., 1998). 4 The maximum contaminant level for William C. Bridges – –1 NO3 in drinking water is 10 mgÁL Department of Applied Economics and Statistics, Clemson University, (National Academy of Sciences, 1977). No Clemson, SC 29634-0313 federal limits on P contamination in fresh- 4 water have been established as a result of Stephen J. Klaine variations in size, hydrology, and depth of Department of Biological Sciences, Clemson Institute of Environmental rivers and lakes and regional differences in Toxicology, P.O. Box 709, Clemson University, Pendleton, SC 29670 P impacts. However, the U.S. EPA recom- mends that total P not exceed 0.05 mgÁL–1 in Additional index words. water quality, Oenanthe javanica ‘Flamingo’, Phyla lanceolata, any streams discharging into lakes or reser- Rhyncospora colorata, Thalia geniculata f. rheumoides, Typha minima voirs and 0.10 mgÁL–1 in streams or other Abstract. Intensive production of container-grown nursery and greenhouse crops in flowing waters that do not (U.S. EPA, 1986). Fertigation runoff in greenhouse crop soilless substrate may result in significant leaching of nutrients and pesticides. The –1 resulting runoff can escape from production areas and negatively impact surface production can contain 100 mgÁL NO3-N and ground water. Constructed wetlands (CWs) have been shown to be a simple, low- (Wood et al., 1999). In nursery crop produc- tion, nursery runoff NO3-N concentrations technology method for treating agricultural, industrial, and municipal wastewater. –1 We investigated the nitrogen (N) and phosphorus (P) removal potential by a vegetated, range from 0.1 to 135 mgÁL (Alexander, laboratory-scale subsurface flow (SSF) CW system. Over an 8-week period, five commer- 1993; Taylor et al., 2006; Yeager et al., 1993) and P levels from 0.01 to 20 mg L–1 cially available aquatic garden plants received a range of N and P (0.39 to 36.81 mgÁL–1 N Á (Alexander, 1993; Headley et al., 2001; and 0.07 to 6.77 mgÁL–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 James, 1995; Taylor et al., 2006). These cited rates were exhibited by Thalia geniculata f. rheumoides Shuey and Oenenathe javanica N and P runoff ranges could be higher or (Blume) DC. ‘Flamingo’, Phyla lanceolata (Michx.) Greene also had high P recovery lower in other nursery and greenhouse crop rates. The potential exists for using SSF CWs to concomitantly produce aquatic garden production systems. plants and attenuate nutrients in a sustainable nursery enterprise. Recently TMDLs of nutrients in agricul- tural runoff were adopted by environmental regulatory agencies in every state (Yeager, 2006). This follows a trend in which state governments have been passing more strin- gent laws and regulations assessing and reg- Received for publication 5 Nov. 2007. Accepted Container production in nursery and ulating nonpoint sources of pollutants beyond for publication 6 Jan. 2008. greenhouse operations using soilless media the scope of the provisions of the Clean Water Act. Support for this project by the Floriculture and involves inputs of fertilizers, growth regula- Constructed wetlands (CWs) have been Nursery Research Initiative for Environmental and tors, insecticides, and fungicides. Repeated Resource Management Practices and Strategies, promoted as an inexpensive, low-technology excessive irrigation leads to leaching and loss USDA Agriculture Research Service, Ft. Pierce, approach to comply with increasingly strin- of nutrients and chemicals in runoff. The FL, is gratefully acknowledged. gent environmental regulations regarding the Technical contribution no. 5386 of the Clemson presence of nutrients in runoff and concerns discharge of nonpoint source pollutants in University Experiment Station. of their impact on surface and groundwater greenhouse and nursery production (Arnold We thank Sarah White, Deidre Jones, and Robby quality has undergone increasing interest Taylor for their invaluable assistance, and Carolina et al., 1999; Berghage et al., 1999). Surface- and scrutiny from the public, environmental flow (SF) and subsurface flow (SSF) CWs Nurseries Inc. and Fafard Inc. for their donations of groups, governmental agencies, and elected plant material and soilless media. are two commonly used wetland designs Mention of a trademark, proprietary product, or officials. Since its enactment, the U.S. Envi- to treat agricultural wastewater (Berghage vendor does not constitute a guarantee or warranty ronmental Protection Agency (EPA) has et al., 1999; Scholz and Lee, 2005). A SF of the product by the authors and does not imply its enforced provisions of the Clean Water Act CW resembles a shallow (0.2 to 0.8 m) approval to the exclusion of other products or (1972) related to point-source pollution. In freshwater marsh and generally requires a vendors that also may be suitable. 1999, the EPA began enforcing nonpoint large land area for wastewater treatment 1Extension Horticulturist. source pollution controls specified in section 2 (Kadlec and Knight, 1996). To remediate Director of Research. 303(d) of the Clean Water Act, which 3Assistant Professor. nursery and greenhouse wastewater, surface 4Professor. mandates that all states implement a Total area can be reduced with a concomitant in- 5Professor and Chair. Maximum Daily Load (TMDL) program for crease in depth (1.25 to 1.5 m), which 6To whom reprint requests should be addressed; all watersheds and bodies of water (U.S. promotes anaerobic conditions that facilitate e-mail [email protected] EPA, 2000). A TMDL is the maximum denitrification. 868 HORTSCIENCE VOL. 43(3) JUNE 2008 JOBNAME: horts 43#3 2008 PAGE: 2 OUTPUT: April 23 09:13:24 2008 tsp/horts/163067/02647 Alternatively, greenhouse and nursery In this study, we investigated a cost- Aquatic Nursery, Johns Island, SC). Micro- operations constrained by limited production effective approach suggested by Adler et al. propagated plantlets of Thalia geniculata f. space and expensive land can use a SSF (2003): ‘‘One way to reduce water treatment rheumoides were purchased from a commer- CW, which consists of a lined or imperme- costs is to produce a product of value con- cial tissue culture laboratory (Agri-Starts II, able basin filled with a coarse medium, comitant with treatment of the water.’’ Apopka, FL). Phyla lanceolata (Charleston typically gravel, and wetland plants (Kadlec Instead of traditional wetland plants, com- Aquatic Nursery) was rooted from 7.6- to and Knight, 1996). Wastewater flows hori- mercially available aquatic garden plants can 10.2-cm long stem cuttings and then individ- zontally or vertically below the surface of be used in a production/remediation system ual plants were transplanted into 15-cm the media to prevent exposure to humans or that could generate revenue. Few studies diameter containers containing a peat/ver- wildlife. SSF CWs can be operated in con- have examined the ability of aquatic garden miculite growing substrate (Fafard Germina- tinuous-flow or batch-load treatment modes plants to thrive in SSF CWs and recover tion Mix; Fafard, Anderson, SC). Plants were with varying hydraulic residence times nursery runoff rates of N and P (Arnold et al., maintained on the greenhouse bench in (Burgoon et al., 1995). 1999, 2003; Holt et. al, 1999). water-filled plastic-lined trays and watered Nitrogen removal from SSF CWs is ac- In an earlier study, we investigated the and fertilized as needed. complished primarily by denitrification and potential of seven aquatic garden plants to The laboratory subsurface treatment plant uptake (Vymazal, 2007). Inorganic or assimilate N and P in a laboratory-scale, wetland was simulated by two polyethylene organic P, which has no valency changes gravel-based SSF CW system (Polomski containers: a 16.5-cm diameter ‘‘azalea’’ during its biotic assimilation or microbial et al., 2007). Louisiana Iris hybrid ‘Full container filled with pea gravel and placed decomposition, is mainly removed through Eclipse’ exhibited the highest N recovery inside a 16.7-cm diameter aquatic container microbial and plant uptake (Vymazal, 2007). rate, whereas similar P recovery rates were (2.8-L container with no drainage holes) so Roots and rhizomes support rhizospheric mi- observed in Canna · generalis Bailey (pro their rims were even. An equilibrium isotherm croorganisms by providing colonizing sites sp.) ‘Bengal Tiger,’ Canna · generalis Bai- experiment indicated no detectable P adsorp- exuding carbohydrates, sugars, amino acids, ley (pro sp.) ‘Yellow King Humbert,’ Iris tion by the pea gravel (Polomski et al., 2007). enzymes, and many other compounds (Rovira, ‘Full Eclipse,’ Peltandra virginica (L.) Two to 4 weeks before the start of an 1969) and oxidizing the rhizosphere (Wießner Schott, and Pontederia cordata L. ‘Singapore experiment, 40 to 50 plants of each species or et al., 2002), which fosters microbial Pink’ (Polomski et al., 2007).