Features Agronomy
Managing nutrients with the four Rs

Best management practices for fertilizer application will differ from golf superintendent to golf superintendent, but it’s all about making the optimum use of available resources.

Speaking in October at the Nutrite/Ontario Seed Company regional fall seminar at Pine Knot Golf & Country Club in Dorchester, Ont., Dr. Eric Miltner, agronomist with Koch Turf & Ornamentals, spoke of the importance of best management practices (BMPs) and how to incorporate them in the optimal and most efficient manner.

“It’s important to think about nutrients more holistically and not just what you buy in a bag,” he said.

Miltner said superintendents should think about how they manage the nutrients in their soils and consider fertilization as supplemental.

Each superintendent’s BMPs depend on available resources, including his budget, his equipment, the knowledge and expertise to which he has access, and the property’s physical nature,

“You have to do it within your own bounds.”

The most common references to BMPs online involve nutrients and water quality, yet BMPs can apply to many things within a superintendent’s operations, Miltner said.

The nutrient management concept has a “cradle to grave” idea that’s not just about thinking about the fertilizer in the bag and how to apply it, but what happens to it afterwards, he added.

Many BMPs are unwritten while others haven’t even been thought about.

“I think there’s a lot to be said about writing down your BMPs and formalizing it.”

The Golf Course Superintendents Association of America has been making a big push in the United States to ensure written BMPs are in place in all 50 states by 2025. The association has been going around to its local chapters that are putting together “boilerplate” BMP documents that individual golf courses can take and apply to their specific properties.

Miltner said there is a lot of value to having written BMPs that can be referenced. Some states require written nutrient management plans on file – including at golf courses – that are approved by certified professionals. This helps to standardize procedures, he said.

“If you have a set of parameters within which you operate, it reduces the chances of you making a bad mistake.”

When a superintendent hires a new employee and charges him with a specific task, the new hire can be provided with pertinent sections of a BMP manual specific to the job.

“This also demonstrates a commitment to your position and your profession that you take it seriously.”

Miltner recalled a Seattle-area superintendent with whom he had once worked, noting the local county was able to better stay on top of its water quality monitoring at his course because of the superintendent’s BMP documentation. The superintendent kept extensive BMP written documents he reviewed with county staff that afforded them the confidence to understand he knew what he was doing. The superintendent had the technical knowledge and a process in place to do the best he could to protect water quality while maintaining his golf course.

“If you don’t have written BMPs, think about it,” Miltner said.

Four R nutrient stewardship
Part of the process is to understand the concept of “four R” nutrient stewardship: right source, right rate, right time, right place. Miltner said it’s easy to understand and convey to groups that don’t possess the technical expertise to educate them about nutrient management. Such groups include greens committees, boards of directors and those involved in the administration of municipal golf courses.

“It’s a great agronomic tool with regard to managing fertilizers.”

Miltner recommended a website called nutrientstewardship.com as a site to learn more. Although it is geared mainly toward the agricultural sector, much of the information is applicable to golf and landscaping and urban nutrient management in general.

“If we all start thinking about this model and start speaking the same language, it’s going to help a lot of people outside our little bubble to understand and appreciate what we do.”

Knowing how to use fertilizers most effectively on a golf course is a “big decision-making matrix,” he said, adding, “There are lots of different right ways to fertilize and it’s going to be different for everybody.”

Miltner said there are also several wrong ways to fertilize.

When considering the right source, he said soluble sources are effective but need to be managed correctly for efficient use to prevent notable loss and unfavourable water conditions. By incorporating enhanced efficiency fertilizers into a program, better nutrient use will be realized as well as stepped up environmental protection and cost efficiency.

In determining the right rate, it’s important to know that there are discrepancies between the amounts of nitrogen to be applied to fine fescue versus that of Kentucky bluegrass. The plant’s growth cycle and the season must be considered.

“Try and provide nutrients when the plant needs it.”

Plants tend to be a little more stressed during the summer and their growth starts to slow.

“What are your objectives in applying that fertilizer?”

The source will have a significant Impact on the rate, Miltner said, adding quick release sources will keep rates lower. If a seasonal fertilizer is applied and the objective is to have it last five months, enough nitrogen must be put down – perhaps 2½ pounds instead of the traditional one-pound application.

He said it’s important to know how the Rs interrelate.

“You might pick the right product – the right source – but if you use it wrong, it’s not going to work for you.”

Generally, a superintendent might think about using a half-pound or full pound of nitrogen per month during the growing season. One pound was the norm in the not-too-distant past but, today, .7 pounds is considered right. Miltner said that because enhanced efficiency fertilizer products work more efficiently, less product could be applied to get the same amount of nitrogen into the plant.

Product longevity and application rate are closely related.

“So make sure you understand what’s in that fertilizer you’re using, how long it’s going to last and how that might impact the rate.”

The right time must be determined by trying to match nutrient availability with periods of growth. The plant is not growing when it is stressed and has difficulty taking up nutrients. This must be taken into consideration when using longer-term products, he said.

As temperatures begin to cool, release rates slow down. If it gets cold enough, they’ll shut down. Fertilizer will sit there and overwinter and be ready to release nutrients in the spring. A three-month product that can work in the fall and spring might last seven months because it is overwintering.

There are plenty of options for the right source and right time relationship, Miltner said.

Enhanced efficiency fertilizers
In an earlier presentation, Miltner outlined the benefits of enhanced efficiency fertilizers (EEFs), including controlled release, slow release and stabilized nitrogen variations.

Anything that can be done to a fertilizer to increase plant uptake and reduce loss to the environment enhances its efficiency. Quick-release soluble sources such as urea or ammonium sulfate work fine, he said, but they can be enhanced so that they work better.

Studies of urea found that about 52 per cent of the nitrogen gets into the top of the turfgrass plant, meaning a pound of nitrogen put down from a urea source will result in only about half of it reaching the plant. If a pound of nitrogen from an enhanced efficiency fertilizer is applied, about 20 per cent more nitrogen gets into the plant.

“That’s a pretty big boost in efficiency.”

EEFs also lead to reduced leaching, less volatilization and reduced denitrification.

Readily available sources that are non-enhanced, such as ammonium sulfate and urea, release quickly. When applied and watered in, nitrogen becomes available within a day or two as long as there is adequate water for dissolving. Once dissolved, the nitrogen is pretty much available, the plant greens up and responds quickly.

“There are certain times when that’s what you really want. But in order to use them efficiently, you have to apply them at pretty low rates and apply them frequently. The reason for that is because the plant can only take up so much at once.”

If more nitrogen is applied than the plant can use, the surplus has to go somewhere else.

Miltner cited a Cornell University study that looked at the plant response of nitrogen when applied in one-tenth-pound increments up to a pound, measuring the amount of uptake versus loss. Different turf species and soil types were examined in the study that found significant inefficiencies were realized with single applications between .3 and .5 pounds of nitrogen.

“After you got beyond one-third or half a pound, that’s when you started to lose it.”

When using non-enhanced efficiency fertilizers, they must be applied at low rates, Miltner said, adding they work well when spoon feeding greens, but volatilization is an issue.

“Applying a pound of N from a soluble source in most cases is a pretty inefficient way to do it. You’re losing a lot of the nitrogen you’re paying for.”

Among the enhanced efficiency fertilizers, stabilized nitrogen is “the new kid on the block,” even though it’s been around for about 15 years. It is produced when a nitrogen stabilizer is added to urea, extending the amount of time nitrogen remains in the soil as either urea or ammonium. The technology doesn’t change the fertilizer – it is still urea and still soluble – but the stabilizers or inhibitors change the way urea is transformed in the soil, creating more plant-available nitrogen.

Urea breaks down in the soil through a chemical process called hydrolysis whereby the urea essentially converts to ammonium. An enzyme from microbes called urease is critical in catalyzing the reaction. If the reaction occurs too quickly, significant amounts of nitrogen can be lost to volatilization. An NBPT (N-[n-butyl] thiophosphoric triamide) urease inhibitor slows down the reaction, keeping the nitrogen as urea for a longer period of time. It slows down the rate of hydrolysis and isn’t lost to volatilization.

Volatilization is more likely to occur in soils that are high in pH, such as those commonly found in southern Ontario that range between seven and eight.

Miltner said single inhibitor products generally have only the NBPT, resulting in more nitrogen getting into the plant. NBPT lasts only a couple of weeks in the soil and doesn’t do much to extend the longevity of nutrient availability. More uptake will occur but without the slow release effect.

With dual inhibitors, both volatilization protection and protection against leaching and denitrification are afforded.

Low analysis fertilizers are less expensive than high analysis formulations, and they contain filler that “doesn’t bring any agronomics to the table.” Although more expensive, the high analysis fertilizers will prove to be more efficient in the end. The cost per bag will be more, but the bigger picture shows there will be a cost savings without filler, he said.

The higher the percentage of EEFs, the more efficiency and longevity are realized.

“The bag might cost you more, but in the end it will save you money.”