Spoon-fed nutrients + automatic irrigation = resource efficiencies

Fertigation, simply defined, is a practice that delivers water-soluble minerals through an irrigation system. Fairly entrenched in the agricultural market, fertigation is arguably in its infancy within the municipal, commercial, and residential arena. Some have never heard of it. Others are slow to accept something new. Some are taking baby steps toward implementation. Others, such as major golf course and sports turf managers, are savvy in its science and serious about its benefits. Successful fertigation systems improve plant and turf health, enrich soil content, reduce the manpower required for fertilization, and increase irrigation efficiency. As most municipalities are charged to do far more with far less, fertigation is certainly an idea whose time should be ripe.

Most often described as spoon-feeding, fertigation is the application of nutrients at the precise rate and time they are needed—the ideal result being that crop yield or turf health is optimized, while less fertilizer (from a 20% to 50% reduction) is being used. And, because well-nourished plants better absorb water, less frequent watering is required. Although it’s difficult to measure how fertigation may or may not affect water conservation, the bottom line is this: Municipal, commercial, and residential landscapes are often over-watered, which can lead to various plant diseases. Then when a decline is seen in the landscape, the tendency is to apply (and waste) even more water.

Proper fertigation practices promote greater root length and density, allowing plant life to store and use water and nutrients more efficiently. Again, this is the ideal result, as successful fertigation is dependent on a number of factors, most importantly that the right fertilizers are chosen and administered at the right rate within any given application. Easy to say, not always easy to do—that’s why some may see the process as being somewhat complex. With that said, we consulted with several of the nation’s top irrigation experts to get their take on the topic.

Benefits and Barriers
“It’s like cable television in the 1970s; fertigation is an idea whose time hasn’t quite arrived yet in the municipal market,” says Tom Kimmell, senior projects director for the Irrigation Association. “In urban areas, there has to be lesser input, whether it’s less fertilizer, water, or other chemicals. Fertigation gives you the ability to do that. It’s something that will come, but we are still going through the learning phases. There are those who are very comfortable doing it routinely; however, it’s probably another decade before it hits the mainstream. But water is a mainstream issue, and as the restrictions regarding it become more stringent, fertigation becomes the next step in the conservation mode.”

Kimmell explains that one of the current barriers is that fertigation spans two distinctly different disciplines. “There are a lot of people who understand irrigation, and a lot of people who understand fertilizers—but there aren’t a lot of people who understand fertilizing through irrigation systems. So fertigation is a great idea, but you have to know something about both ends,” he says, adding, “The fertilizer people want to sell fertilizers and the irrigation people want to sell irrigation technology, so you have to find someone who bridges both—and that is likely to be someone who specializes in liquid fertilizers.”

Charles Burt, chairman of the Irrigation Training and Research Center (ITRC) at California Polytechnic State University, says his best advice to those new to fertigation is to keep it simple. “The problem with fertigation is that it involves chemistry combined with the nuances of plant growth, and many people involved in municipal management are not very comfortable with chemistry. So initially it’s best to create a fertigation program that’s easy to maintain,” says Burt. “The primary element applied via fertigation is nitrogen. Most other elements can be applied in the traditional way as they do not have transformation. Nitrogen is pretty dynamic. It washes away, and it changes shape, volatilizes, and goes into the air. The other elements in plant nutrition generally stay in the soil where you put them,” he says.

Burt stresses that the hardest thing is matching the fertilizer rate to the application or precipitation rate. “If they put on 3 inches of water, they ought to put on ‘x’ pounds of nutrients—and most people don’t know how to match the two. Until we have easy, ready access to liquid fertilizers and the people who understand them, it will be a challenge. Most people don’t even know where to get liquid fertilizers and that is a drawback,” he says.

A comprehensive resource, says Burt, is the publication entitled Fertigation, which can be ordered at the ITRC Web site at www.itrc.com.

Fertigation Is a Best Management Practice
Reagan Waskom, water resources specialist at Colorado State University, says that best management practices are the key to effective fertigation. “The greenhouse and nursery industries, as well as the center-pivot irrigation sector, have fertigation well in hand. The adoption curve is not quite there in many urban applications or in the lower-tech irrigation [residential and commercial] sectors—and that is due to the way that urban landscapes are managed. We have the industry that comes in to fertilize and spray, and then we have our sprinkler systems. People just want to set those and walk away. Low-level management situations are not appropriate for fertigation. If you have phosphorous and nitrogen running downhill, that’s a big issue. You must have the right backflow prevention in place, and that has to be maintained and managed. That may be a part of what is so daunting about it,” he says.

Fertigation requires an upfront investment in technology and people. As such, some municipalities and commercial properties are outsourcing their fertigation management and maintenance contracts to the liquid fertilizer supplier, for example. “Automated fertigation requires that you formulate your batches correctly and that you properly check and calibrate the system. That requires skilled workers. Yes, fertigation is a management tool that saves time, labor, and resources—but if calibration is off and the fertilizer rate is off, you may be doing more harm than good in terms of water quality and nutrient waste,” says Waskom.

System Implementation
“A lot of municipalities already have the irrigation systems in place. They have the central control systems that will handle all the timing issues related to fertilizers. They can fertilize multiple sets using these central control systems—they just need the hardware to apply it, as well as the backflow preventions,” says Kimmell of the Irrigation Association.

Typically, the fertigation system comprises injectors or pumps, a controller, and a plug-in transformer. The injector is installed on the irrigation system’s main line. The injector pulses each time that a signal is emitted from the controller. Every pulse injects about 1 milliliter of fertilizer into the mainline. The system operates by controlling zones, with each zone being programmed to deliver different amounts of fertilizer for the requirements of the given zone.

“By knowing the number of square feet or acreage that they are going to treat, we can size the pump to meet the application rate. All of our pumps are micrometer-adjusted systems, making them easy to adjust,” says Arnold Page, manufacturer’s representative for Agri-Inject Inc., a company formed in 1982 to serve the fertigation needs of the agricultural community. Its founder, Gary Newton, is said to have coined the term fertigation when he was experimenting with the techniques in the late ’60s. In more recent years, the company formed a division called IIT to serve the landscaping industry as well.

“These systems will pay for themselves very rapidly, just in labor costs. There are systems out there still operating after 20 years, when maintained properly,” he adds.

Page says that systems may range in price from $2,500 up to $20,000, depending on the bells and whistles.

Virtually any irrigation system that delivers water relatively uniformly is suitable for fertigation, if the fertilizer is applied frequently at low application rates. However, drip irrigation is often more desirable. Its main advantage is water conservation, as a drip system requires about half as much water over the growing season as sprinkler irrigation.

Measuring Results
Fertigation experts agree that the way you evaluate its success is by looking at efficiency, cost savings, and plant response. “The thing about nitrogen is that you get a pretty quick feedback as to whether you are providing sufficient amounts. Most good turf managers know when they have too little nitrogen or too much,” says Waskom.

Next, put a pencil to the labor savings and to the elimination of operating and maintenance costs for dry fertilizer application equipment, and to the percentage of fertilizer reduction.

Do the math, and perhaps it will be clear that fertigation is an idea whose time should be now.

Construction-industry writer Carol Wasson owns JCL Marketing & Communications Inc.