Tools for Clean WateR3 at your Nursery and Greenhouse

By Jim Owen, Ph. D., Associate Professor, School of Plant and Environmental Sciences, Virginia Tech and Sarah White, Ph.D., Professor, Clemson

The recently completed Clean WateR 3 project funded by USDA-NIFA comprised five years of research and innovation to Reduce water use, Remediate contaminants and pathogens, and aid in water Recycling. Scientists and cooperating nursery and greenhouse growers aimed to increase profitability, secure water resources, and develop tools to manage water for reuse or release offsite. Project results led to a greater understanding of the chemical, economical, physical, and social dynamics within nurseries and greenhouses, providing systems-wide strategies, including web-based tools, to help growers better manage water. Simultaneously, the carbon and water footprints of crops, ranging from boxwood to begonia, were analyzed and reported by Drs. Ingram and Hall. This and more can be found at http://www.cleanwater3.org/.

Agrichemicals, including water soluble and controlled release fertilizers, are used to produce ornamental plants in soilless substrates. Soilless substrates tend to have little water holding capacity, resulting in potential for agrichemical and sediment runoff. Drs. David Sample and Jim Owen’s team at Virginia Tech demonstrated nutrient runoff load from nurseries are similar to that of urban runoff, with 35+ times greater total nitrogen and phosphorus runoff during a storm than during an irrigation event. Sediment runoff is greater in nurseries, regardless if rain or irrigation driven, when compared to urban runoff. Sediment can carry latent agrichemicals (think phosphorus and pesticides) that can eventually impact on-site collection water reservoirs or local ecosystems if sediment leaves the property.

Existing and new Best Management Practices (BMPs) can be employed to reduce agrichemical and sediment movement at your operation. First, irrigation should be scheduled to apply only the amount of water needed when it is needed. Additionally, micro-irrigation should be used whenever economically feasible to minimize non-target water application that does not go to the individual plant and thus contributes to excessive runoff. These approaches to irrigation will minimize water handling, water treatment, and associated energy or chemical costs in addition to improving water security at time of drought.

Nurseries and greenhouses should routinely conduct inhouse trials to determine if substrate, fertility, integrated pest management strategies, or growth control products can be modified to be more profitable and further improve environmental stewardship. Dr. Owen’s lab demonstrated that amending pine bark with fiber, Sphagnum peat and coir, can improve storage of available water for a given plant between irrigation events resulting in less water stress and potentially less production time. Concurrently, his lab identified that current substrate extract and foliar phosphorus sufficiency ranges are greater than needed. The phosphorus content of water soluble or controlled release fertilizers can be reduced by 25% or more when producing six economically important woody ornamental shrubs without reducing shrub quality or size. Drs. Jake Shreckhise and Owen also found that incorporating common amendments (lime and micronutrients) reduced phosphorus leaching from containers both at planting (70%) and throughout the growing season (50%). Amendments could potentially be considered an “automatic” BMP.

Similarly, Dr. Chris Wilson at the University of Florida found that common substrate components pine bark and peat retained at least 80% of imidacloprid, mefenoxam, and paclobutrazol residues; incorporation of water treatment residuals or similar amendments may be needed to increase retention or decrease movement of acephate and imidacloprid. Dr. Tom Fernandez at Michigan State University demonstrated effective remediation of pesticide residuals using woodchip bioreactors for 20 minutes, reducing bifenthrin by 49%, chlorpyrifos by 73%, and oxyfluorfen by 25%. Woodchip bioreactors also consistently reduced nitrate concentrations from 80 ppm to less than 1 ppm. In greenhouse production, Dr. Paul Fisher and his team at University of Florida found that paclobutrazol laden water, regardless of pH, was effectively treated (>90% reduction) when passed through a granular-activated carbon system for approximately one minute. In a follow-up study, Dr. Fisher reported using the same system to eliminate (i.e. below detection) residual acephate, flurprimidol, paclobutrazol, uniconazole, chlorine (free and total) from production runoff. The granular-activated carbon system was also able to reduce bifenthrin, chlorpyrifos, imidacloprid, glyphosate, triclopyr, and hydrogen peroxide by more than 70%.

Sediment basins at nurseries and greenhouses are used to remove and retain sediment before water is reused for irrigation or leaves the production site. Photo credit: Sarah White

Nursery and greenhouse runoff from irrigation and storms can affect surface water quality before water is reused for irrigation or leaves the production site. Photo credit: Sarah White

Additional BMPs to slow and reduce sediment movement and the agrichemicals carried with it include covering production surfaces with fabric or plastic, lined or vegetated strips or ditches, vegetative channels, riparian buffers, and flow control structures that slow water, allowing sediment to settle out. Flow control structures include filter socks, detention ponds, and in-line sediment traps that are easy to clean out and maintain. Additionally, Dr. Darren Haver at University of California has demonstrated 80% or more reduction in sediment using a negatively charged polyacrylamide (PAM) deployed via PAM incorporation into filter socks. Polyacrylamide can also be incorporated into “curtains” at the inlet of a pond, to encourage sediment settling.

Pathogens remain tricky, however. Dr. Jennifer Parke’s team at Oregon State University determined a simple method for growers to test irrigation water for Phytophthora using Rhododendron leaves or pear fruits as bait. Using an inexpensive diagnostic test kit to confirm that the brown spots emerge are potential disease, subsequent water treatment with chlorine was shown to be effective means of control. Concurrently, Dr. Loren Oki’s team at University of California found slow sand filters (SSF), once populated by community of microorganisms, can provide quality water from irrigation runoff by breaking down Phytophthora and tobacco mosaic virus; SSF did not effectively eliminate Fusarium.

Floating treatment wetlands, rafts upon which plants are grown can also mitigate sediment, agrichemicals and pathogens. Drs. Sample, Sarah White, Lauren Garcia Chance and Laurie Fox reported floating treatment wetlands planted with Pontederia cordata or Panicum virgatum removing more than 65% of total N and P after establishment of approximately five weeks. Drs. White and Natasha Bell established Pontederia cordata in floating treatment wetlands and noted a reduction in the number of viable Phytophthora zoospores that flowed through a vegetative channel under flow rates typical of cyclic nursery irrigation patterns. Additional work is needed to quantify and verify longterm efficacy of floating treatment wetlands for Phytophthora remediation.

This is only a brief summary of accomplishments and potential new tools for increasing efficiencies in nursery and greenhouse water management investigated as part of Clean WateR 3 project. We encourage you to visit the CleanWateR3.org website, managed by Dr. Fisher and his team at the University of Florida, to learn about other water management tools, to ask a question, find answers to your water problem, peruse our research, watch recorded webinars, and sign up for trainings and the newsletter.

The experimental nursery at Virginia Tech’s Hampton Roads Agricultural Research and Extension Center being used to understand the response ofcrop growth to reduced water use, varied substrate hydrology, andsubsequent agrichemical fate in runoff and leachate. Photo credit: JimOwen

Substrate and crop interactions are studied at the soil-plant-air continuum lab at Virginia Tech’s Hampton Roads Agricultural Research and Extension Center. Photo credit: Jim Owen

Virginia Tech CleanWateR 3 Leaders

James “Jim” S. Owen Jr., PhD Associate Professor & Extension Specialist School of Plant & Environmental Sciences Hampton Roads Agricultural Research & Extension Center jsowen@vt.edu • (757) 363-3904

David J. Sample, PhD, PE, WRE Associate Professor & Extension Specialist Biological Systems Engineering Hampton Roads Agricultural Research & Extension Center dsample@vt.edu • (757) 363-3835

Laurie Fox, PhD Horticulture Associate School of Plant Environmental Sciences Hampton Roads Agricultural Research & Extension Center ljfox@vt.edu • (757) 363-3807

Jim Owen is the Virginia Cooperative Extension Nursery Specialist and an ex officio board member of the Virginia Nursery and Landscape Association since 2012. Dr. Sarah White, professor and Extension Specialist at Clemson University (swhite4@clemson.edu), is the leader and project director of Clean WateR 3 project.