Potassium fertilization essential for turfgrass health

Potassium fertilization is more valuable to turfgrass that a lot of folks think, says a golf course maintenance company agronomist.

Dr. Jeffrey Higgins, director of agronomy for Valley Crest Golf Course Maintenance, says he’s as much concerned with proper potassium levels as he is with nitrogen, especially on golf course greens, where stress level is high.

“There has been some debate in the industry about the importance of potassium,” Higgins says. “But in areas like the Southeast and the entire country this past summer where heat and other stresses take a toll on turfgrass, we need it.”

Higgins works across the country for Valley Crest but lives in Birmingham, Ala., where heat and humidity can play havoc with bentgrass greens, as well as high stress areas such as tee boxes.

“We use potassium for the entire year,” Higgins says, “and especially prior to heavy stress periods … summer and winter.

“We typically apply a polymer-coated sulfate of potash product after core aeration in the spring and sometimes in the fall. That slow-release product provides 20 to 24 weeks of potassium release into the soil solution. We apply between 2 pounds to 4 pounds of K per 1,000 square feet and brush the product into the open aeration holes.”

Potassium, he says, is very water soluble and also lacks binding strength to the cation exchange sites. So potassium is short-lived in the soil, especially on greens, where percolation rates are higher and nutrients are more susceptible to leaching.”

He says golf course superintendents have two basic options for potassium application: make a lot of applications of soluble potassium or make fewer applications with slow-release products. “We use a combination of both approaches. We apply the polymer coated product as a base supply of potassium at aeration and we supplement potassium throughout the year as needed through liquid applications.”

The fall application encourages turfgrass to “to harden off the cell walls before winter stress comes on,” he says. “Potassium is a protective mechanism and encourages cell walls to be more woody and hardened off versus fat, juicy cells that are deficient in K and more prone to environmental stresses and damage.

“We typically apply a 16-0-32 fertilizer blend to large acreage areas such as fairways in the fall, he notes.

“We like potassium sulfate on greens. Potassium sulfate doesn’t burn turf due to its low salt index. “As we get away from the greens we can switch from potassium sulfate to muriate of potash and manage accordingly to reduce burn potential by applying to dry turf and watering immediately after application.

“Some Florida golf course superintendents may apply as much as 40 pounds to 50 pounds of potassium per year; we don’t typically apply that much,” he says.

He likes at least a 1:1 ratio of nitrogen to potassium and prefers it at 1:2. “I feel like potassium is more valuable than some managers think,” he says. “If a golf course can afford it, I would use a 1:2 ratio across the entire course.”

Higgins uses tissue analysis to determine potassium demand. “Soil tests are not as representative of what’s going on in the plant,” he says. “Tissue tests are more accurate.”

A good baseline is 1 percent potassium in the tissue samples, he says. “Anything above that baseline is good. For the rest of the course, application rates may depend on the budget.”

Tees get a good bit of attention and may need more potassium because of heavy traffic and damage. “Fairways and other areas get a blended fertilizer that includes some potassium in the fall.”

Golf course management has changed in the last few years, partly due to the recession, Higgins says. And not all those changes have been negative.

“We seem to have lost a lot of common sense over the years,” he says. “The economic slowdown convinced many managers to get back to the basics of maintaining turfgrass‚sunlight, water and fertility. In some ways, it’s been a healthy change.”