Comparative Nutrient Remediation by Monoculture and Mixed Species Plantings within Floating Treatment Wetlands.

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.

Short- and long-term dynamics of nutrient removal in floating treatment wetlands.

Floating treatment wetlands (FTWs) are a plant-based treatment technology shown to remove excess nutrients and metals from surface waters under a variety of conditions. Plants established in FTWs can accumulate and store nutrients within their tissues, but the amount of uptake and storage is dependent on plant species and nutrient influent concentration. This research was designed to quantify the influence of nutrient load and two plant species on nutrient uptake and partitioning patterns within plant tissues (shoots and roots) so that management recommendations for FTWs can be developed to better protect surface water quality. Treatments consisted of (1) two nutrient loads: a high concentration of 15 mg⋅L-1 nitrogen (N) and a low concentration of 5 mg⋅L-1 N supplied as water soluble fertilizer, and (2) four mesocosm treatments: (a) open water, (b) artificial mat only, no plants, (c) artificial mats planted with Pontederia cordata L., and (d) artificial mats planted with Juncus effusus L.. Plant growth, N, and phosphorus (P) uptake of both P. cordata and J. effusus were greater in the high nutrient treatment than in the low. Pontederia cordata facilitated the highest rates of N (0.31 mg.L.day-1) and P (0.34 mg.L.day-1) removal. The nutrient removal rates facilitated by Juncus effusus in the high nutrient treatment were much lower for both N (0.03 mg.L.day-1) and P (0.02 mg.L.day-1). Peak N and P accumulation in J. effusus occurred in September within both root (50 g N and 4.8 g P) and shoot tissues (98 g N and 12.5 g P). The uptake of N and P in P. cordata was highest in root tissues in August (307 g N and 30.5 g P) and in shoot tissues in September (1490 g N and 219.5 g P). In both species, shoots accumulated more N and P than the roots, resulting in a small root:shoot ratio at all stages of the experiment. Harvest of plants from FTWs should occur before plants senesce in the fall, which using P. cordata and J. effusus as model species, occurred from mid- to late-September in USDA Hardiness Zone 8a in the Southeastern United States.

Water Use and Treatment in Container-Grown Specialty Crop Production: A Review.

While governments and individuals strive to maintain the availability of high-quality water resources, many factors can "change the landscape" of water availability and quality, including drought, climate change, saltwater intrusion, aquifer depletion, population increases, and policy changes. Specialty crop producers, including nursery and greenhouse container operations, rely heavily on available high-quality water from surface and groundwater sources for crop production. Ideally, these growers should focus on increasing water application efficiency through proper construction and maintenance of irrigation systems, and timing of irrigation to minimize water and sediment runoff, which serve as the transport mechanism for agrichemical inputs and pathogens. Rainfall and irrigation runoff from specialty crop operations can contribute to impairment of groundwater and surface water resources both on-farm and into the surrounding environment. This review focuses on multiple facets of water use, reuse, and runoff in nursery and greenhouse production including current and future regulations, typical water contaminants in production runoff and available remediation technologies, and minimizing water loss and runoff (both on-site and off-site). Water filtration and treatment for the removal of sediment, pathogens, and agrichemicals are discussed, highlighting not only existing understanding but also knowledge gaps. Container-grown crop producers can either adopt research-based best management practices proactively to minimize the economic and environmental risk of limited access to high-quality water, be required to change by external factors such as regulations and fines, or adapt production practices over time as a result of changing climate conditions.