COVER STORY
Clean WateR TOOL S FOR
3
A T YOUR NURSERY A ND GREE NHOUSE
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 WateR3 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.
12 • VNLA News • Winter 2019
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
