Protective potassium

When winter hits brutally hard, a drought lingers, rain falls for weeks on end or a golf course sees unprecedented play, turf becomes susceptible to stress. Researchers note that keeping potassium levels up helps to mitigate some of that stress.

Potassium helps protect turf from stresses related to drought, heat, cold, traffic and salinity, says Dr. Travis Shaddox, assistant professor of turfgrass at the University of Florida.

The vital nutrient manages the osmoregulation of water in turf, Shaddox says. “At no point does potassium ever actually enter into an organic compound,” he says. “It never enters into, say, a protein or an enzyme. It never enters into anything like that, but it helps facilitate the production of those by keeping the plant imbibed with water.”

Turf sees more response from potassium when the nutrient’s levels are low in the tissue versus when they are high, Shaddox says. When cold creates a stress on turf, the plant needs to already have sufficient levels of potassium in order to keep water flowing.

In the event of stress, potassium works better as a preventative measure than as a curative one, Shaddox says. “In my professional opinion, I wouldn’t necessarily look at it as, ‘Ok, we’re about to get cold, let’s go throw a bunch of potassium out,’ or, ‘It hasn’t rained in two weeks, let’s go throw a bunch of potassium out,’” he says. “I don’t think that’s really the wisest philosophy to use. What I would recommend is simply ensuring that potassium is sufficient as frequently as possible.”

If superintendents put out a little bit of potassium every month or two, they will be better prepared for a number of stresses than if they put out a large application once a year, Shaddox says. “I would look at it as a resource to minimize future problems,” he says. “We don’t necessarily want to walk through the desert, become dehydrated, and then drink water. We want to walk through the desert and drink a little bit of water so we never become dehydrated.”

Some evidence points to potassium’s ability to itself alleviate stress symptoms in certain situations, but how exactly the process works is still up for debate, says Shaddox, adding that it is likely due to potassium’s ability to keep turf hydrated.

Although it is one of the primary turf nutrients, along with nitrogen and phosphorus, the consensus about potassium’s importance to turf has changed multiple times over the years, says Dr. Nick Christians, professor of turfgrass management at Iowa State University. “Many years ago — go back 25, 30 years ago — we probably underestimated the importance of potassium in turf management programs,” he says. “We then went through a period of time where we probably overestimated it and people were making too high a recommendation on it. Now we’re probably going through a time period again where we’re underestimating the importance of potassium. So it is something that needs more work.”

A large portion of Christians’ work with potassium has focused on growth response, he says. “But we do know that there’s a lot of subtle things that go on in the plant related to stress — related to winter survival, summer survival, drought survival, all these sorts of things,” he says.

Various environmental and abiotic stresses, such as traffic and regular play, can limit turf’s ability to take up water and nutrients, including potassium, says Dr. Larry Murphy, owner of Murphy Agro and consultant for Compass Minerals.

The process of diffusion, when water carries potassium through the soil toward the plant root, is slowed down by cold temperatures, Murphy says. “The lower the temperature, the more difficulty the plant would have in obtaining adequate amounts of potassium from the area out away from the immediate vicinity of the root,” he says.

Compaction is an issue brought on by traffic, weather and other conditions that limits potassium uptake, Murphy says. “The fact of the matter is that there is less oxygen in the soil when there is compaction, because there are fewer pore spaces, and less oxygen means that energy-producing reactions in the plant, which drive uptake of nutrients, are limited,” he says. Like in the case of excess water, oxygen supply is limited in the case of compaction.

Potassium uptake also becomes limited when water moving into the root contains a high concentration of dissolved salts, Murphy says. Often, this water contains high amounts of chloride. “One of the things that Compass stresses about potassium sulfate compared to potassium chloride, for instance, is that many species are quite sensitive to chloride,” he says.

In events of heat and drought stress, turf plants are simply not taking up enough water to receive adequate levels of nutrients, Murphy says. Heat events that limit the uptake of potassium are comparable to drought events that cause leaves to stop exchanging water vapor and roots to become inactive.

“Potassium does help mitigate these stresses, which range all the way from heat to cold to traffic to poor water quality,” Murphy says.

Patrick Williams is a Cleveland-based turf writer and frequent GCI contributor.