With recent advances in the understanding of nutrient behavior, smart lawn care professionals are creating more efficient fertilization programs. LCOs are turning fertility management from something of an art form to a science. Different climates, rootzone mix composition, lawn care professional's expectations and budgets all play a role in modern turf nutrition.
A recent study from the Penn State College of Agricultural Sciences confirms that turfgrasses require at least 16 nutrients for growth and development; some nutrients are needed in large amounts, while others are only necessary in minimal quantities.
Nine of the 16 required nutrients are needed in much larger quantities. These nine nutrients - carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium and sulfur - are called macronutrients. Carbon, hydrogen and oxygen make up about 90 to 95 percent of the plant's dry weight. These are rarely deficient in turfgrasses because they are derived from carbon dioxide (CO2) and water (H2O).
So it's crucial that the three remaining primary nutrients that are not present - nitrogen, phosphorus and potassium - be supplied periodically to turf through fertilizer applications.
Fast, slow or controlled-release?
Define your expectations; choose the fertilizer that meets your goals. For example if you want an immediate response from turfgrass, apply uncoated fertilizers. This type of fertilizer is particularly successful stimulating quick growth in cool-climate soils. When the soil is too cold, which effects microbial activity, fast-release fertilizers can provide the necessary amount of nitrogen yielding a quick response and results.
Effects of fast-release fertilizers are oftentimes short-lived (two to four weeks) because of rapid depletion from the soil due to leaching of nitrates. Also, in some cases fast-release fertilizers can even result in burning when applied too heavily.
Multiple factors affect the nutrient release of slow-release fertilizers. These include soil moisture, temperature and soil pH level. Slow-release fertilizers are typically more affordable than controlled-release fertilizers and best used when precision is not a concern. Fewer applications are needed with slow-release fertilizers but nutrients may not be available when the plant needs them.
Controlled-release fertilizers provide both precision and predictability. Unlike slow-release fertilizers, controlled-release fertilizers are affected by one factor: soil temperature. This makes the nutrient release predictable offering continuous release of nutrients through a permeable membrane coating throughout the growing season.
"With controlled-release fertilizers, lawn care professionals can achieve optimal nutrition in a single application at reduced rates allowing for cost savings on labor, fuel and other overhead fertilization costs," says Dr. Bob Raley, agronomist, Direct Solutions, a green industry distributor based in Loveland, Colo.
Researchers are now finding that a fall fertilization program can offer additional benefits that carry well into the next year. Recent studies at The Ohio State University show that overall plant and turfgrass physiological health is improved for the following season with a fall fertilizer application.
Researchers at Penn State University have also noted that applying nutrients such as phosphorus and potassium in late fall can maximize root growth and plant maturation, as well as enhance turf's hardiness, disease resistance and wear tolerance into the following summer.
"The benefits of a fall fertilization program are growing beyond the aesthetics of providing seasonally greener turf," says Raley. "LCOs can reduce the amount of fertilizer they use, and a fall feeding sets up the turf to become healthier, denser and better able to withstand the stresses of summer."
The ideal time for fall fertilization varies, largely dependent on soil temperatures so that root systems are still active and can store nutrients. Regardless of the timing, the benefits of a fall program are changing the landscape of fertilization programs.
Controlled-release ferts improve spring turf
A fall feeding, particularly with a controlled-release fertilizer, can help turf develop deeper roots during the spring. The key is preserving valuable carbohydrate reserves for root development that might otherwise be depleted by excessive shoot growth, which often results from early spring fertilization. That vital growth can lead to stronger, healthier plants that can endure summer hazards such as pests, increased wear and seasonal stress conditions.
Fertilizer manufacturers accomplish a controlled-release reaction with compounds that bind with the highly soluble nutrient sources or by encapsulation of the fertilizer source within a water-insoluble coating. The purpose of a controlled-release fertilizer is to prevent 100 percent release of the nutrients immediately following application, but instead to promote metered feeding based on soil temperature.
Premium products release nutrients through a propriety polymer coating. By varying the thickness coatings, these fertilizers release nutrients at different speeds. This extends the time of feeding to ensure nutrients are delivered when the plant's rootzone is most ready to absorb the nutrition.
Joe Grandstaff is the athletic facilities manager at the James W. Cownie municipal sports complex in Des Moines, Iowa, a state-of-the-art venue with 12 soccer fields and eight baseball diamonds. Field users insist on exceptionally high-turf quality.
The site annually hosts thousands of sporting events, from local leagues to national youth soccer championships and Division I college games. In order to efficiently attain superb turf, in 2012 Grandstaff decided to make a change by replacing his traditional fertilizer program with a premium controlled-release fertilizer (Spread it & Forget it).
"After applying the controlled-release fertilizer just once, our fields stay healthy and have continuous, consistent, vibrant color for the following five months," says Grandstaff. "Spread it & Forget it (a controlled-release product offered by Agrium Advanced) offers reduced cleanup and environmental impact, which supports Leadership in Energy and Environmental Design (LEED) certification standards for municipal properties."
Moisture levels do not affect the controlled-release fertilizer. A single application continues to deliver nutrients to the turf's rootzone gradually and evenly, month after month.
"Since we've implemented a controlled-release product to our fertilizer program, with just one application compared to the traditional five applications, we've reduced maintenance costs," says Grandstaff.
By eliminating the amount of fertilizer applications during the season, turfgrass professionals reduce the risk of damage to equipment, structures, monuments and other hardscapes. Unlike quick-release fertilizers, heavy rainfall or irrigation won't trigger excess nutrient release resulting in surge growth.
The controlled-release product performed exceptionally well on our soccer fields, he adds. "Soccer is constant running, turning and diving. Soccer is the true test of a product like this," says Grandstaff.
The importance of timing
Fall fertilization yields an increase in rooting, maximizing root growth of cool-season turfgrasses that occurs in spring and fall. Some root growth will occur in winter if temperatures are above freezing, whereas little if any growth occurs in summer. During fall fertilization in most regions the roots are still growing at a time when shoot growth has ceased, thus allowing the roots to make full use of the fertilizer.
"When fertilizer is applied in late fall there is an increase in the plant's carbohydrate reserves that occurs," says Raley. "Turfgrasses accumulate carbohydrates in stems and roots during fall, which gives turf an advantage to resist winter injury and aid in disease and environmental stress resistance the following spring and summer."
He adds, "The environmental, economic and efficiency benefits of fall fertilization, especially with a controlled-release fertilizer, are hard to ignore," adds Raley. "They span the fall, winter and spring seasons, and create greener, healthier turf that uses resources more effectively."
With today's technology, by choosing the right fertilizer, often times a controlled-release fertilizer, nutrients will be gradually released into the soil, staying in the rootzone, to feed turf only when its needed. Technological advancements have allowed for deeper understanding of nutrient behavior to develop advanced products, offering LCOs options to formalize an efficient fertilization program that ultimately saves time and money.
Dr. Eric Miltner is agronomist, turf specialist at Agrium Advanced Technologies. He is a former associate professor at Washington State University.