Defining Enhanced Efficiency Fertilizers (EEFs)

What are EEF's?

Enhanced Efficiency Fertilizers (EEFs) are: "Fertilizer products with characteristics that allow increased plant uptake and reduce the potential of nutrient losses to the environment (i.e. gaseous losses, leaching or runoff) when compared to an appropriate reference product." - AAPFCO, Official Definition

Enhanced Efficiency Fertilizers (EEFs) in turf & ornamental management are a specialized category of fertilizers designed to optimize nutrient delivery to turfgrass while minimizing environmental impact and maximizing efficiency. These fertilizers incorporate technologies such as controlled-release, slow-release, or nitrogen stabilizers to provide a steady and sustained supply of nutrients to the turf over an extended period. By releasing nutrients gradually, EEFs help to prevent nutrient leaching, runoff, and volatilization, reducing the risk of environmental pollution and maximizing nutrient uptake by turfgrass.


Additionally, EEFs can be customized to meet the specific nutritional requirements of different turfgrass species and environmental conditions, promoting healthier, more resilient turf with improved color, density, and overall quality. Overall, enhanced efficiency fertilizers play a crucial role in promoting sustainable turf management practices and maintaining high-quality playing surfaces for various applications, including sports fields, golf courses, and residential lawns.

Types of EEF Technologies

Controlled-Release Fertilizer

A controlled-release fertilizer is a nutrient source (often urea or sulfate of potash) coated by a polymer layer, regulating gradual nutrient release into the soil. This specialized coating ensures controlled dissolution of nutrients while allowing gradual outward flow through the polymer. Factors like temperature and soil moisture influence release rates. These fertilizers can vary in coated thickness to provide nutrients to plants over weeks to months, reducing application frequency compared to conventional fertilizers. Controlled - release fertilizers enhance nutrient efficiency, minimized leaching, and improve turf and ornamental quality. Polymer-coated controlled-release fertilizers are pivotal in agriculture, horticulture, and landscaping, offering a balanced and efficient approach to plant nutrition and soil fertility management.

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TTRU blue fertilizer granules in a pile

Polymer-coated fertilizers (PCFs) release nutrients based on osmosis and diffusion through the coating. Water passes through the polymer outer layer and dissolves the nutrients inside. Nutrients then move through the coating in response to a concentration gradient (high concentration inside the coating, low concentration outside the coating). Release rate and longevity are controlled by coating thickness and soil temperature.


Because the release follows a known temperature response, PCFs provide a predictable, controlled release of nutrients over a desired timeframe (typically 2 to 12 months). Release is minimal when soil is cool and increases with rising soil temperatures to coincide with plant growth and nutrient demand.


Golf course superintendents have utilized controlled-release fertilizers for decades to help manage the wide range of nutritional needs their courses require. Fewer applications, less labor and flexible programs are among some of the advantages. Professional sports field managers, landscape professionals, lawn care operators and specialty ag growers are bringing enhanced efficiency fertilizers (EEFs) more into play for the same reasons.
Controlled-Release Fertilizer →


Slow-Release Fertilizer

Slow-release nitrogen (N) sources, also called "slowly available," are a part of many turfgrass fertilization programs. They provide greater longevities of available N than quick release sources, and are safer to use on turfgrass because of their lower burn potential. This group includes both coated and uncoated sources.

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Sulfur-coated urea (SCU) fertilizers are granules of urea coated with sulfur and wax. Imperfections (cracks, fissures, fractures) in the coating allow water to move in and dissolve, then release the urea. For fertilizer particles with coatings that are intact after application, water movement through the coating results in internal osmotic pressure that cracks the coating, releasing nutrients. This process has been called catastrophic release. In addition, microbial degradation of the wax and sulfur allows water to reach the urea, dissolving and releasing it.


XCU green and blue granules in a pile

Polymer-coated sulfur-coated urea (PCSCU) fertilizers are an evolution of this technology. A polymer layer around the sulfur provides more protection than the wax, resulting in a longer and more predictable nutrient release.


XCU® slow-release fertilizer represents the next generation in sulfur coating technology. The order of coatings has been inverted. Urea is coated by a thin layer of polymer, then sulfur, followed by wax. The sulfur protects the ultra-thin polymer, which helps to regulate nitrogen (N) release via diffusion. The release mechanism of XCU® fertilizer is a hybrid of catastrophic release and diffusion. Because of the improved performance provided by the polymer layer, PCSCU nutrients are released more consistently over a longer time than traditional SCUs.


Reacted urea products are a type of slow-release fertilizer based on complex N compounds. These are commonly known as urea-formaldehyde (UF) and methylene urea (MU). Reacted urea is an uncoated technology that stores N in organic molecules of varying chain lengths and requires microbial activity (linked to soil temperature) for release. This slows the release of N, as only one chain link is released at a time, making it available to the plant over a longer period. Typically these products contain about 30-40% N with longevities of 8 to 26 weeks.


The reaction process during production is controlled to produce varying chain lengths. These chain lengths determine nutrient release and longevity.
Slow-Release Fertilizers →


Stabilized Nitrogen Fertilizer

Inhibitors/stabilized nitrogen fertilizers work by delaying the conversion of N to forms that can be more readily lost to the environment through leaching, denitrification and volatilization. This delay allows time for rainfall or precipitation to move the urea into the soil where it is less prone to volatilization, and/or retains N in the plant/soil system longer. There are two main categories: urease inhibitors and nitrification inhibitors.

TECHNOLOGIES AVAILABLE

DuoTech product powder with a beaker in front with dissolved DuoTech that is creating a teal transparent liquid

Urease inhibitors work above the soil to slow the conversion of urea to ammonium through hydrolysis. Slowing this conversion retains more N as plant-available ammonium, with less converted to ammonia gas that is then lost to the atmosphere through volatilization.


Nitrification inhibitors work in the soil by slowing the microbial conversion of ammonium to nitrate. Ammonium can be held on soil exchange sites and available for plant use. Negatively charged nitrate is susceptible to leaching and denitrification, especially under wet conditions or in coarse-textured soils. Nitrification inhibitors can reduce these losses, typically for up to 8 weeks.


Stabilized nitrogen can be applied as a spray or spread as a granular, giving your customers the flexibility to tailor their fertilizer programs.


Stabilized nitrogen fertilizers work well in all soils, and may be especially valuable where pH is high, and where a lack of irrigation, high precipitation or over-irrigation exists. Steep slopes are also a good area for this source, because stabilized nitrogen solubilizes upon watering so particle movement or migrating is not a concern.
Stabilized Nitrogen Fertilizers →


EEF Release Factors

What Factors Can Affect EEF Nutrient Release

For any fertilizer—including enhanced efficiency fertilizers (EEFs)—these environmental factors contribute to how and when each releases nutrients, and the rate of that release.

Water

In water soluble or quick-release fertilizers such as urea and ammonium nitrate, water dissolves the source and nutrient release is immediate. Although turfgrass response is rapid with these fertilizers, too much water makes nitrogen (N) prone to leaching and runoff.


Stabilized nitrogen is based on urea, so water is important in solubilizing the fertilizer. The presence of inhibitors retains N in plant-available forms longer than non-amended urea though, making the N less prone to loss.

In controlled-release and slow-release fertilizers, water is utilized to dissolve the nutrient inside the granules. Although it does serve as an activator, water may impact the release rate of sulfur-coated products, but does not impact the rate for polymer-coated fertilizers.

Temperature

Both ambient and soil temperature can affect the release of nutrients to the plant. High temperatures can also increase the potential for ammonia volatilization.


In the case of controlled-release fertilizers, temperature impacts the rate of diffusion, the primary control on nutrient release. Controlled-release fertilizer release rates therefore increase with rising temperatures, and vice versa.

Microbial Activity

Soil microorganisms also impact how and when some EEFs release. Methylene urea (MU) and urea-formaldehyde (UF) fertilizers, as well as natural organics, rely on microbes to break down the fertilizer, releasing nutrients through mineralization.


Microbes can also degrade the coatings of sulfur-coated fertilizers, enabling nutrient release. Microbial activity is generally higher in warmer soil temperatures and less active in colder conditions, so temperature impacts the release rates of these EEFs.

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