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Potassium, Hokkaido, and Snow Mold

I'm at snow-covered Hokkaido for some seminars this week and one of the things I have mentioned in the seminars is the possible increase in snow mold damage that can occur with high rates of potassium application in the fall season. Dr. Kerns mentioned the research being done at Cornell now to investigate this phenomenon.

We came across this observation on an L-93 field trial that we had designed to study soil testing methods, not snow mold. What we found, as you see below, is that plots treated with potassium in the previous year (and to which no fungicides were applied to prevent snow mold) had an increase in snow mold damage compared with plots to which no potassium had been applied in the previous year.

In both 2003 and 2004, when the snow had melted from the research green, we observed a linear increase in gray snow mold damage with increasing rates of potassium application.

Hokkaido has heavy snow mold pressure. Many of the golf courses are under snow for four months. The photo below shows the effect of fungicide application in the fall (at right) vs. no fungicide (at left) in the snow mold damage to a golf course rough at Obihiro in mid-May. Clearly, one would not want to exacerbate the disease intensity by unwarranted application of potassium.

10 Responses to “Potassium, Hokkaido, and Snow Mold”

John Kaminski said...


Do you know how the K was applied. In other words, was the 75 kg K/Ha (~1.5 lbs/1000 sq ft) applied all in one shot just prior to autumn or was this the total amount spaced out over the course of the season?


Micah Woods said...

The potsassium was applied every 14 days throughout the growing season, as a liquid application. This was basically an evenly distributed rate of K applied from May until November each year. Note that the 75 g K rate is per square meter, so that is more like 15 lbs/1000 sq ft per year. In our measurements of disease intensity in that experiment, however, there was a linear increase in disease intensity with increasing application rate of K.

John Kaminski said...

Thanks for the clarification.

Holy crap that's a lot of K! What is the normal use rate of K per year in that area?

Micah Woods said...

Yes, that is a lot. In north Asia, the typical K application rates on an annual basis would be 50% to 100% of the N rate. I think a little bit of K is alright, but too much is very likely to be rather detrimental.

Lane said...

Great post, Micah, thanks for sharing. I think this is a very important issue. Many golf course superintendents are applying excessive K, especially to golf course greens, because it is supposed to improve 'stress tolerance'. The increase is snow mold is a great example of how too much of a good thing can be worse than nothing. Burt McCarty showed a similar effect with spring dead spot in his PhD research at NC State. They saw an 90% increase in the disease in plots that received 6 lbs K per 1000 ft2 in the previous year.

Ok I am in NJ what would you recommend for maintaining a decent level of K? I hear to apply K to help the plant harden off before the winter then I hear that it causes snow mold. i hear you need K then I hear you don't. What is a poor golf course super to do???

Jim said...


That is a good question. From some work that Doug Soldat has done at UW, he found that Phosphorous works like a light switch. In other words it does not work like a gradient. They found that at 5 ppm P the plants look terrible, but at 7 ppm the plants look fine.

We really do not know if K is the same way. Basically I would suggest to monitor your soil K levels and apply accordingly.

What do you say Micah??

Micah Woods said...

What is a golf course super to do?

In all the field, laboratory, and library research I have done, it seems that 50 ppm of K on a standard soil test is a good sufficiency level. If you apply K at half the N rate, your soil K will tend to stay relatively stable because the plant is taking up about the same amount of K that is being applied.

The benefits of K that we hear about, hardening off the plant, stress tolerance, etc., are something that are provided already when K is present in sufficient amounts.

Jon said...

Was all of the Potassium in sulfate form or chloride? The only reason I ask is that greenkeepers in Austria use Kali, which is the chloride form of potassium, as a winter treatment before snowfall but after the turf is somewhat dormant. I thought they were crazy but the superintendent I was working with left a check. Sure as heck, the check had lots of snow mold and the treated tees had very little. My theory was the salt actually was antagonistic to the snow mold. I have made that recommendation to superintendents who want to use potassium in the winter and no one ever came back to hang me.

Micah Woods said...

That is interesting. In the experiment we did, the potassium was applied in the sulfate form and we stopped applications before the turf went dormant.

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