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"After the RWS canisters are installed, they provide both water and oxygen to tree roots," Foster explained. "It's much more efficient than watering trees by hand above ground or even with ground-level bubblers because the RWS virtually eliminates evaporation." If the RWS is installed correctly, it can effec- tively serve a young tree for seven to 10 years. For longer-term tree watering, RWS units can be placed at two different tree perimeters, each on a different watering zone. One perimeter can be closer to the root ball to help during the first couple of years. The second perimeter can be placed further way from the trunk to provide watering in subsequent years. During the first few years, only the internal RWS zone would be used; in the subsequent years, the external RWS zone would go into effect. This provides a long- term tree water system in order to promote broader and deeper roots. Although Rain Bird was sure that the RWS benefits trees and shrubs, the company wanted to gather specific statistics about the system's effec- tiveness. As a result, Foster and others worked with plant scientist and researcher Dr. Ursula Schuch of the University of Arizona's School of Plant Sciences. Schuch developed a study that examined the growth and survival of 48 ash trees transplanted at a test site. "We irrigated half of the 48 trees with a pair of Rain Bird RWS-M 18-inch canisters installed adjacent to the root ball," Dr. Schuch said. "The remaining 24 trees were irrigated at ground level with bubblers near the trees' trunk." All 48 trees received the same amounts of water with the same frequency. Schuch and her staff then harvested the trees at three, eight and 13 months after transplantation to collect data for the study. Just three months after transplanting, Schuch and her staff found that the trees irrigated below grade with the RWS canisters had 50 percent more deep-root growth, and after 13 months they had about 20 percent greater root mass and 11 percent larger above ground mass than the trees watered with surface bubblers. "Having that greater root mass not only helps trees tap a larger soil moisture reservoir, it also anchors them more securely in the landscape," said Schuch. "This gives them a solid start to get established in their new location. For newly transplanted trees in relatively unprotected, wind-prone areas, this is especially important." Foster went on to explain that many people think the surface water a tree receives from sprinklers is adequate because the tree appears to be growing normally. "The fact is that when a surface- watered young tree gets larger — perhaps four years or so after transplanting — a windstorm could come along and easily blow it down," Foster explained. "All its roots are just below ground level because that's where their water supply has always come from. Systems like the RWS help avoid this situation." Foster added that systems like the RWS can still improve tree www.landscapeirrigation.com health even when they're not connected to an automated water source. "There's an absolute benefit for un-plumbed versions of these deep root watering systems," Foster explained. "You can still install two or three of the RWS canisters below grade. Rainwater, drainage water or water from a hose can then fill the canisters and effectively reach the roots. The water doesn't have to filter through the soil to get to the place where it's needed most. The canisters also provide valuable aeration to the tree roots. It's an especially ideal option in lower areas of the landscape that may receive too much water and can really benefit from some drainage assistance." Although the benefits of this type of root watering system are very apparent for commercial and public tree-planting projects, Foster believes there's definite opportunity in the residential mar- ket as well. "Right now, I'd say that 85 to 90 percent of the RWS we sell are for commercial and institutional-type projects," Foster said. "This type of product is typically something that an architect or specifier would select to match the needs of a particular com- mercial site. However, design-build contractors are in an excellent position to offer a product like the RWS to their customers. No one wants to lose a tree that they just purchased and had planted. By emphasizing both the immediate and long-term benefits of root watering, along with the indisputable data from our Univer- sity of Arizona study, there's an opportunity for contractors to in- crease both revenue and customer satisfaction." Lynette Von Minden is senior public relations counsel at Swanson Russell, Lincoln, Neb. Article provided by Rain Bird Corporation. Landscape and Irrigation 27 LI