Quick & Easy

When it comes to maintaining healthy turfgrass, superintendents are often forced to make a basic, but very important, choice ... control versus convenience. Does the control of spoon feeding liquid nutrients into the turf outweigh the convenience of slow-release granular products?

Quick- and slow-release granular products are effective management tools, especially under less intensive management, says William Kreuser, assistant professor of agronomy and horticulture at the University of Nebraska-Lincoln, but Mother Nature and ever-changing turf needs make spoon feeding a more effective option.

“A management goal for a highly maintained turfgrass system is to sustain consistent turf performance throughout the entire growing season,” Kreuser says. “Nitrogen availability typically has the greatest impact on turf performance including color, density and traffic tolerance. Unfortunately, the nitrogen cycle is extremely dynamic and complex. This makes it difficult to sustain even nitrogen availability.”

An effective way to manage a complex system is to use simple, quick-release, fertilizer sources, he says. These products, such as clean urea or ammonium sulfate, are easily dissolved and sprayed on highly maintained turfgrass.

Every time we make an application to our turfgrass we introduce the small chance of an application error or mistake. They can be large and acute, like a hose blows on a sprayer and dumps a lot of mix directly into the environment, or small and chronic, like some fertilizer drift off-site and off-target if it is too windy.” — William Kreuser, University of Nebraska-Lincoln

“This allows managers to be very flexible with application rates depending on what the turfgrass needs,” Kreuser says. “It also means that the fertilizer will be immediately available for nutrient uptake. Superintendents who successfully use liquid spoon feeding of nutrients constantly assess the quality and performance of their turf and tweak fertilizer application rates and frequencies to sustain consistent performance and quality.”

Ultimately, foliar quick-release nutrients gives turfgrass managers the greatest amount of control, Kreuser says.

Turf researcher Doug Soldat likes the practice of spoon feeding because it provides so much control.

“If the turf looks green, you can leave the nitrogen out of the tank ... If it looks hungry, you can add a bit more than you normally do,” says Soldat, an associate turfgrass professorat the University of Wisconsin-Madison’s Department of Soil Sciences. “We are learning that there are advantages to manipulating potassium levels in leaf tissue. Sometimes you want it above 2 percent, other times there are benefits to having it around 1.5 percent or lower. These manipulations are best done by spoon feeding potassium fertilizer, rather than attempting to adjust soil potassium levels.

Soldat doesn’t believe there are any special benefits to foliar uptake, in particular.

“You sometimes hear that there are situations where roots aren’t functioning and foliar uptake then becomes an important pathway for assimilating nutrients,” he says. “However, if your roots are truly non-functional, then you have other problems (like water uptake) and your plant won’t live. Roots evolved to take up nutrients, while leaves evolved to keep liquid out. So while I prefer liquid feeding in most cases, I don’t get hung up on getting my nutrients in through the leaves rather than the roots. That said, if you are interested in getting the nutrients in the plant through the leaves, use a small spray volume, a urea based nitrogen source, and a product that contains an adjuvant to spread the solution out along the leaf.”

Foliar applications, though, have many advantages.

“First, the approach provides turf managers greater control over nutrients applied,” says Travis Shaddox, assistant professor at the University of Florida/IFAS Fort Lauderdale Research and Education Center. He focuses on soil fertility and turfgrass nutrition with a strong emphasis on granular and liquid fertilizers, in his research. “Environmental conditions may vary greatly after nutrients are applied - ie. excessive rainfall events, etc. Foliar programs allow for a more rapid reaction and greater flexibility to offset unfavorable environmental conditions.

In addition, foliar applications greatly increase the application accuracy, especially when very low quantities are needed, Shaddox says. “Nutrient rates of 0.1 to 0.25 lbs. of an element are commonly applied. This would be very difficult to accurately apply using granular nutrients,” he says.

Lastly, Shaddox adds “application uniformity” for the same reasons listed in above.

Today’s practices are not only good for the quality of the turfgrass, but there are environmental benefits, as well. Precision nutrition, as Shaddox terms it, may have a positive environmental impact by reducing the total amount of nutrients required, since those nutrients are often more efficiently utilized by turfgrass systems.

Weather comes into play, too, Soldat says. “Spoon feeding ensures that there isn’t an excess of nutrients in the soil to wash away if a heavy rain event occurs,” he says. “The small doses applied by spoon feeding are taken up in a matter of hours, not days.”

Application of low rates of soluble fertilizers have a positive environmental impact because the low applicate rate reduces the risk of nutrient loss when large applications of nutrients are applied at one time, Kreuser says. He adds another benefit is that the risk of removal during mowing is greatly minimized compared to granular products. The collection of these fertilizer prills during mowing and subsequent clipping piles increase the risk of nutrient leaching.

There are environmental concerns to consider, however.

“The risk of an application mistake would be magnified when more applications are required over the year,” Kreuser says. “Every time we make an application to our turfgrass we introduce the small chance of an application error or mistake. They can be large and acute, like a hose blows on a sprayer and dumps a lot of mix directly into the environment, or small and chronic, like some fertilizer drift off-site and off-target if it is too windy.”

Human error is the main worry, Shaddox says.

“Theoretically, any concerns are insignificant since there is overwhelming evidence that foliar nutrition is more efficient and less wasteful than a normal granular program,” he says. “However, in practice, humans make mistakes, storage and handling can create issues, and spills can occur. As long as the products are shipped, handled, stored and applied appropriately, foliar nutrient applications to turfgrass are very safe.”