Irrigation Notebook: May 1997, Fertigation In The Field

The potential benefits are indis-putable, but how feasible are these systems?

SYSTEM BASICS. "Basically, liquid fertilizer is injected into the main discharge line of the irrigation system right at the water source," explained Van Cline, manager of research and development at The Toro Company’s Agronomics Division, Minneapolis, Minn.

The fertilizer is held in separate tanks located at the irrigation pump station. "The injector pump and control system work as a flow sensor installed in the irrigation line to use the concept of proportional flow so the system is always applying the right amount of nutrients," said Cline.

SPLIT SQUAD. Fertigation systems have long been popular on golf courses and have seen a rise in popularity with sports turf applications lately. Some manufacturers are preparing to bring this technology to commercial applications and even residential irrigation systems.

"The same technology that is now used to care for the most sensitive turf around — golf courses — is now being brought downstream for smaller applications," enthused Michael Chaplinsky, owner, Turf Feeding Systems Inc., Houston. Chaplinsky, a manufacturer of fertigation systems, admitted that many systems available now can be cost prohibitive for smaller, residential applications. But he expects much more affordable products to be on the market in the near future.

"This is new technology for irrigation contractors right now," noted Kurt Maloney, director of marketing and sales for the landscape division, Netafim Inc., Fresno, Calif. "But if the system is set up correctly and the contractor understands mixing and pro-portioning of concentrates, it’s simple and efficient to use."

Not all manufacturers are ready to produce fertigation systems. In fact, only a few manufacturers are actively pursuing this market.

"Fertigation systems can present problems because the uniformity of the application is directly related to the layout and performance of the irrigation system," noted Jeff Carowitz, marketing manager, Hunter Industries, San Marcos, Calif., who said fertigation is not currently a product development prior-ity for Hunter. "Fertigation is becoming more popular, but it’s not something that can be used to replace fertilizer applications."

TURF BENEFITS. "Golf course fertigation has proven the value of feeding turf smaller dosages of nutrients regu-larly as opposed to feeding it large quantities three times a summer," noted Chaplinsky.

The theory behind this method of feeding turf is that when fertilizer is applied regularly (whenever the irri-gation system is activated) in much smaller doses, contractors can maintain a constant level of nutrients in the plant tissue and in soil that are constantly available for uptake.

"This way you’re always providing the turf with the nutrients it needs, as opposed to overwhelming it with as much fertilizer as it will take three times a summer," Cline added. "This will result in healthier, more vigorous turf."

Proponents of the system also claim fertigation provides more homogeneous applications because of the liquid formulation and the opportunity for a greater level of product control.

ADDRESSING CONCERNS. The presence of fertilizers can cause concern among some governments or municipalities. "If a contractor is using a potable water supply, he or she has to have a very high-end backflow preventer, because of the potential for mixing the product with the city’s water supply," added Carowitz.

"Proving the system has proper backflow prevention is critical to comply with regula-tions," recognized Cline. "Some areas won’t allow these systems, but most just require good backflow systems.

"There’s a common concern among contractors that the fertilizer will corrode and ruin the system, but that’s never been a problem," he continued.