Fertigation: Breaking Down the Misconceptions

by Allen Olson, EcoDose Fertigation Systems USA & President GDR Systems

What Is Fertigation?

Dr. Max Brown, part of the Agronomic Systems Division of The Toro Company, first defined turfgrass fertigation in the early 1970s as the accumulation of four important ideas; the first being the injection of liquid fertilizers into an irrigation system mainline at the point of connection. Secondly, it is the frequent application of light amounts of nutrients, such as nitrogen, potassium and sulfur not easily stored in the soil. Thirdly, fertigation is the blanket coverage over all irrigated areas with nutrient-bearing water. Lastly, it is the controlled release of fertilizer via the controlled application of fertilizer.

History Of Fertigation

In an article by Bill Nolde, staff agronomist writer for California Turf and former golf course superintendent, it was pointed out that fertigation has been around for a quite some time, but has only recently begun to impact the golf industry. He explained that the agriculture and nursery industries have successfully applied fertigation techniques to crops for over 30 years. The green “crop circles” that can be seen from airplanes over the Western US are an example of fertigation on a mass scale. The center pivot irrigation systems used to create crop circles use fertilizer injectors to apply nutrients during each irrigation cycle to as much as 600 acres.

Nolde also noted that fertigation technology has been undergoing a refining process parallel to the advancements being made in fertigation injection equipment. The technology advancement for turfgrass applications focused primarily on golf courses. In fact, turfgrass fertigation can be traced back to Dr. Brown who pioneered the techniques at his company, Liquid Ag Systems, Inc. Over the past ten years, others like Dr. Brown have installed hundreds of sophisticated golf course fertigation systems around the world using electronic injection metering pump systems.

Fertigation systems now exist to deliver golf course quality turf to all types of landscapes. It has been refined to become a simple way to consistently balance nutrients to various plant materials. Steadily injecting small amounts of elements through the irrigations system can efficiently maintain an optimal supply of specific plant nutrients as well as reduce water consumption, particularly in sandy soils.

Why Fertigation?

Fertigation is time-efficient and cost-effective for everyone from homeowners, to lawn care companies and of course, golf superintendents. In contrast to fertigation, granular fertilization methods involve frequent applications of significant amounts of time-release fertilizers. These fertilizers usually contain two sets of chemicals; theoretically, about halfway between applications one releases immediately while the other releases a few weeks later.

The result of such applications is a massive dosing of fertilizer, which is followed by sudden and excessive leaf growth with little root development. The initial dosage is used up fairly quickly while the nitrogen, potassium and other chemicals dissipate in a matter of days. Once the initial chemicals are gone, the grass begins to starve, creating significant stress on the plant.

In the meantime, much of the chemical designed to release later was washed off higher areas of the turf into the lower areas or creeks and stormwater systems. A common problem occurs when the second chemical releases. Lower areas of turf experience another massive dosing and growth spurt, while the higher areas continue with little additional nourishment. This is followed by another starvation period until a new treatment and cycle is repeated. Regardless of the delivery system, this method is an unhealthy and ineffective means of fertilization.

Advantages Of Fertigation Over Traditional Fertilization

There are several key benefits to incorporating fertigation into a golf course irrigation system. For example, it is understood that compounds of nitrogen are vital in the life processes of all plants and animals. According to the study “Nutrient Management for Micro Irrigation”, by Donald Pitts, a Water Management Engineer at the Southwest Florida Research and Education Center in Immokalee, Florida, the use of nitrogen injection in the fertigation process reduces potential leaching by applying the nitrogen, as the plant requires it. Thus, excess nitrate is not present to be leached in the event of a heavy rainfall.

Pitts further explains in his study that a comprehensive evaluation of the water source allows the user to identify the nutrients that must be added to the fertigation process, as well as to the degree and frequency. Phosphorus, potassium and other such minerals can significantly enhance the production of vegetation when carefully monitored with fertigation.

To determine appropriate amounts of liquid fertilizer injections, Pitts suggested the following equation:

Vf = (a A) / (c d)

where:
Vf = liquid fertilizer volume (gal)
a = application amount (lbs / ac)
A = area (ac)
c = concentration source (N – P – K, decimal)
d = density (lbs/gal)

For example, determine the amount of fertilizer to inject for the following conditions. The fertilizer source is urea ammonium nitrate (32-0-0) with a density of 11.05 lbs/gallon and the application amount is 10 lbs per acre.
Vf = (10 x 100) / (0.32 x 11.05) = 282 gallons

Pitts concluded in his study that water and chemicals should be applied based on hydraulic characteristics of the irrigation system and the water holding capacity of the soil. This conclusion validates the use for fertigation over traditional granular fertilization methods.

Fertigation Specifics

1. FINANCIAL BENEFITS OF FERTIGATION

• Slow-release fertilizers cost significantly more than soluble, liquid fertilizers
• Less energy and equipment is required in the application of soluble fertilizer through fertigation
• Reduced maintenance and repairs on the tractor and spreader
• Labor time spent on spreader equipment is reduced
• Enhanced application time for complete turf coverage
• 10 to 20 percent faster rate for acceptable turf

The following is an example of a typical grow-in comparison of liquid vs. granular:

ASSUMPTIONS:
• 100 acres of turf
• 10 lbs Nitrogen per 1,000 square feet total for grow-in
• Application rate of 1 lb of nitrogen per week

>Product Cost/Ton Application (Cost/Acre) Total Cost/Acre
28-3-10 50% SCU $500.00 $4.00 $42.83
20-2-5 Liquid $300.00 $0 $32.62

Liquid Advantage: $10.20 per acre
Total Savings: $10,205.00 per grow-in

2. REDUCED RATES OF FERTILIZATION

• Plants feed at slower rates and develop healthier root structures
• Plants require less water
• Plants are more resistant to disease and insect infestation.
• Fertigation defeats excessive growth that follows heavy fertilizations and the slow growth at the end of conventional fertilization cycles.
• Less overall fertilizer use due to effective fertilization

Typically, granular, quick release fertilizers applied topically and watered into the grass responds in a few days with a burst of color and an increased succulent growth rate that requires excessive mowing for a week or two. Then, when the color starts to wane in a few weeks, the typical procedure is to fertilize again, resulting in severe roller-coaster growth rates that stress plants, weaken cell structures and invite disease and pests.

3. PLANT GROWTH FEATURES

• Stronger root structures
• Enhanced pest and disease tolerance
• Soils serve as a bank for nutrients like calcium, magnesium and phosphorous.
• Fertigation can be used to deliver nutrients at appropriate levels for plant availability
• Spoon-feeding nutrients reduces leaching by eliminating application rates that exceed the turfgrass’ capacity to absorb them

4. INCREASED CONTROL OVER NUTRIENT ALLOCATION

• Nutrients are carefully monitored and regulated with a fertigation system
• Exact amounts of fertilizer are applied to turfgrass when appropriate
• Users are able to set an exact mixture to control growth and color
• The chance of burnout or streaking by over-applying fertilizer are decreased
• Excessive growth, thatch and disease are reduced

5. NATURE FRIENDLY

• Smaller concentration of chemicals
• Enhanced absorption rate
• Less runoff is available to contaminate stream, river and ground water

6. UNIFORM SOLUBLE NUTRIENT DISTRIBUTION

• Enhanced foliar absorption allows plants to consume nutrients with greater ease
• Consistent applications throughout the rootzone decrease the chance of being washed away or leached out of the soil prior to plant uptake
• Deep watering adds to the rootzone’s nutrient reserves
• Energy is taken from top growth and converted to root growth

The genius of fertigation lay in its ability to place unprecedented control of nutrient distribution into the hands of course superintendents and turf managers. Granular distribution can be difficult to control once it has been applied to turf. The fertigation process, however, gives turf managers the confidence that exact amounts of nutrients are being applied when and how they should. The result is dependable and consistent growth of lush, vibrant grass.

ECODOSE FERTIGATION PUMPS & SYSTEMS

Are you looking to start fertigating or just looking for a more precise and reliable solution, we can help.
See our range of positive displacement plunger pumps with variable speed and Brushless DC Motor Technology here or contact us for information on systems or custom requirements you may have.

All our pumps are designed and manufactured in Australia; are simple to install & use (just dial in the flow you need – LPH, GPH or custom metric, even while the pump is operating); and can easily be added to your current irrigation and farm controls.

Sources Cited:
Nold, Bill. September/October 1996. California Fairways, “Fertigation Strategies”.
Pitts, Donald. 1994. Micro Irrigation Management Workshop Series. Southwest Florida Water Management District. Immokalee, Florida.