10 tips for recycling irrigation water

Editor's nore: The management of irrigation water is a top concern of ornamental growers who are affected by fresh water depletion, as well as the introduction of agricultural water regulations. This is the culmination of a multipart series. See the sidebar for details on previous articles.

1. Be proactive. Designing a recycling system on your own terms – before your local government adopts laws or develops “one size fits all” regulations – can give you more flexibility, assuming that systems already in place will be grandfathered. You can shop around for the right system, target your investment where it is needed most and customize it for your operation. Nurseries may benefit from a tail-water recovery system, while greenhouses may want to consider flood floors. Growers in New Jersey who took this approach are ahead of their competitors and already adhere to the kinds of regulations imposed elsewhere.
 

2. Consider all the options. UV light, chlorine gas, ozone, microbial treatment, and copper ionization to name a few. These techniques can be used for many sizes and types of operations. They each have pros and cons that should be considered. For instance, UV light bulbs are safer than chlorine gas, but cannot be used to treat irrigation runoff with high silt content. There are many variations among water management systems, depending on the type and size of operation. The number of tail water recovery basins used by a nursery depends on the topography and layout of their operation, and more can be built to accommodate for expansion. Greenhouse irrigation water can easily be recycled because the water is collected afterward and can be chemically, physically, or biologically treated.
 

3. Learn from the experience of your fellow growers and visit as many businesses as possible. For personal accounts refer to previous and future articles in Greenhouse and Nursery Management Magazines that chronicle five growers’ experiences in New Jersey. They have dozens of years of experience and are eager to share the lessons they learned. For example:

• Some plants do not respond well to chlorine treatment, such as crimson pigmy Barberry and certain types of Spirea.
• A vacuum system for chlorine treatment is reliable, but an automated system with regulators and sensors based on oxidation-reduction potential (ORP) is safer.
• Chlorine treatment or ozone may be antagonistic to controlled released fertilizer, but the growers I spoke to did not experience that.
• It is important to ensure that tail-water recovery systems do not transport chemicals and diseases from one area of your property to another.
• Using smaller flood floor systems with multiple feeds allows for more versatility with chemical and fungicide treatments.
• If the ozone level in the water is too high, it will burn the roots and could lead to Pythium.
• Water must have some electrical conductivity for copper ionization to work successfully.
   

4. Filtration is key. Build the largest reservoir possible to hold your water pre (and possibly post) disinfection. This increases the amount of natural filtration as sedimentation occurs and large organic chunks sink to the bottom of the reservoir. All nurseries we interviewed agreed that the placement and size of retention basins was key to the success of their recycling systems. One nursery recently expanded his system to include a second catch basin that holds his water after disinfection to increase the dwell time of chlorine treatment.
 

5. Plan ahead and anticipate future expansion to allow for versatility with watering. One nursery built its tail-water recovery system 10 years ago and it is already outdated and does not contain all of the runoff. The New Jersey growers involved in this research have protected their businesses by controlling their water use before it is mandated by the state. On the other hand, growers in California have struggled in the face of strict water laws and several have gone into bankruptcy.
 

6. Recycled water can spread disease and must be properly disinfected. One crop loss could cost 10x more than the amount to install and operate a disinfection system. Water disinfection ensures that plant pathogens are not being recycled along with the irrigation water. An integrated approach with physical, chemical, and biological treatments is most effective.
 

7. Be prepared to invest in both the original system as well as ongoing maintenance. Financial rewards may not be immediately noticeable, but may accrue long term. Water recycling also may appeal to a more environmentally-conscious customer base. Many growers have experienced a positive community response and have used their practices as a marketing tool.
 

8. Look into cost sharing from the Natural Resource Conservation Service (NRCS). It is a federal program that provides financial and technical assistance to private landowners. They help to plan and implement conservation practices to help save energy, improve soil, water, plant, air, animal, and related resources on agricultural lands.
 

9. Have realistic expectations. Many of the benefits of recycling irrigation water are difficult to quantify: recycling creates a private reservoir for nurseries, increases fertilizer efficiency, improves plant health, can be used as a marketing tool, and is a proactive water management practice. Growers experience a ‘feel good’ effect by protecting the environment. Most of these will not correlate to immediate increased income, and the most significant monetary benefit is the foregone cost of drilling additional wells.
 

10. Consider the alternative. Recycling may not be for you if you are concerned about the biohazard risk of spreading disease. An alternative such as drip irrigation reduces water requirements tremendously. This type of water management (a wet/dry cycle) also can improve the root-to-shoot ratio of plants.

Alyssa DeVincentis is a recent graduate from Rutgers University. She completed her honors thesis on water disinfection and recycling at horticultural operations throughout New Jersey under the guidance of Dr. Robin Brumfield, professor and Farm Management Specialist, and Dr. Paul Gottlieb.