"Sorry if this is a rubbish question"

This question came some months ago:

"I'm just pondering something about MLSN levels for Bent vs Poa and so hopefully you can clear it up.

Having seen a bit of research coming out about k levels affecting disease pressure differently for poa and Bent does that not mean there should be two different MLSN's for the two species?

Sorry if this is a rubbish question, I might have missed something somewhere."

That is not a rubbish question. There are three general points I'd like to make about this.

  1. MLSN is a method for interpreting soil tests to prevent deficiency. That is, MLSN is designed to be conservative. The MLSN guideline serves as a quantity of K in the soil that the grass will never touch. The amount of K recommended as fertilizer using the MLSN approach differs based on three things: grass type, growth of the grass, and the quantity of K in the soil. The fertilizer recommendation for K changes for every situation, but the MLSN guideline remains the same.

  2. This article by Doug Soldat has more about varying K fertilizer amounts and bentgrass and Poa annua diseases. If one wants to adjust the K fertilizer in an attempt to incite or suppress anthracnose or snow mold, or winter kill, then one might err on the side of a little bit more K for Poa in summer, and a bit less K for bentgrass, especially in autumn.

  3. MLSN is meant to be simple, and is meant to answer two questions. Is this element required as fertilizer? If the answer to the first question is yes, then the second question it answers is "how much of the element is required?" It is meant to err on the side of recommending too much, rather than too little. One can use those recommendations as a reference, and then if one wants to try to reduce the intensity of snow mold, then cut the K.

The two green system usually means there are two bentgrass greens per hole

The idea that golf courses in Japan with the two green system have a summer green and a winter green is not quite correct. Nor is the two green system used exclusively with one warm-season grass green and one with cool-season grass.

image from
Trevor Dormer and I had a brief discussion about this.

Survey data I looked at some years ago showed 37% of courses in Japan use the two green system. That number will be slightly lower today. But I expect most courses with the two green system will have two bentgrass greens. It does vary; a busy course near Tokyo has one Champion ultradwarf bermudagrass green and one korai (Zoysia matrella) green. And there are courses with one bentgrass and one korai green. I've written about this a lot. A selection of posts on this topic are at the bottom of this page.


But for now, here's what I saw on a recent trip to Japan. When I visit golf courses and talk with greenkeepers, I often ask these questions.

  • How many holes, one or two green system, and what grasses?
  • How many maintenance staff do you have?
  • What is the number of rounds at this facility?
  • How much nitrogen do you apply per year to the greens?

Of the nine facilities I visited last week, here's the answers to those questions from the greenkeepers. Six gave the N rate. The minimum was 11 g N/m2/year, the maximum was 20 g, and the median was 13; 3 greenkeepers didn't have the number off the top of their head. The other data are in this chart.


The median staff was 15 people, and that includes everyone -- mechanics, part time staff, office staff, etc. This is actually a bit high for Japan. I was visiting facilities skewed a little to the high end. I think the nationwide average staff will be 12 or 13 people per 18 holes.


The median rounds were 44,000 per year. That seems about right. The course with 80,000 rounds has night golf and one can tee off until 21:00.

And how about the greens? I visited 9 courses. Of those, 2/3 had two greens. Of those with two greens, 1/3 had one bent and one korai, and 2/3 had two bent.


More about the two green system in these posts.

The Winter's Tale

There are more surprising photos from Doug Soldat this week. Where potassium fertilizer was applied, there is more snow mold. Where potassium was not applied, there is less snow mold.

This photo, starting in the top right plot with the lowest amount of snow mold, and going clockwise, is:

  • top right, no K for six years
  • bottom right, no K for six years but high K added from August to October 2016
  • bottom left, high K for six years
  • top left, high K for six years but no K after August 2016.

It's not so surprising, actually.

Doug has been observing these results for some years now. See, for example:

Preventing nutrient deficiencies


The recording of my webinar on preventing nutrient deficiencies is now available in the videoteca section of the Campus del Césped website.

Or watch the English version right here.

This was fun. I hope you'll read the handout too. It is only 4 pages, with lots of white space, and gives a brief overview of this important topic. If you are still interested, then watch the video of the webinar at your leisure, and watch or download the slides too.

Links in English

Links in Spanish

How to lose 120 million yen with frost delays

I'm bombarded at this time of year with reminders, notices, descriptions, and articles telling me about the importance of frost delays. Apparently, frost delays are essential for the health of the turf. Allow play on frozen or frosted turf, and the leaves will turn brown and start to die. In a worst case scenario, recovery from the damage could take months.

This is a story about something completely different. How about no frost delays at all, and removal of snow by any possible method so the course can remain open? That's the approach used at well over 1,000 golf courses in Japan. I guess there are about 600 courses that are at such a high elevation or are so far north that they close for the winter; at the remaining courses, golf is a year round sport.

I will admit, I was terrified to allow play on frosted turf when I was a superintendent in Japan. I'm sure I protested, explained how much the grass would be damaged, said I would not take responsibility for the damage, and so on. But much to my surprise, the damage was negligible and temporary.

I wrote about how temporary the damage is in this post about winter traffic on frozen bentgrass. As a follow-up to that, I was asked if it mattered if it was a leaf frost or a ground frost. I said I didn't know, but I would look up the temperatures from that winter and share some more details of my experience.

Here's the story.

This was at Habu CC in Chiba prefecture. The greens were Penncross creeping bentgrass, the tees and fairways were Tifway 419 bermudagrass overseeded with perennial ryegrass, and the roughs were noshiba (Zoysia japonica). Here's the 15th in November.


The course is at an elevation of 120 m. I downloaded the daily temperature data for the winter of 2000/2001 from the nearby JMA Sakahata weather station, which is also at 120 m. I think these temperatures are similar to those at the golf course.


From 29 November 2000 until 2 April 2001 there were 73 days with a low of 0°C or below. I think frost can form on the leaves even when the air temperature is above 0°C, but I'll stick with 73 days as an estimate of mornings with frozen or frosty turf.

In Japan, it is customary to do a two tee start, with tee times at 7 minute intervals, the golfers stopping for a meal at the clubhouse before starting their second nine. At Habu, there were about 3,000 rounds per month in the coldest months of that winter -- maybe more -- and 4,000 to 5,000 rounds per month in November, March, and April.

I wanted to implement frost delays, but it was impossible. The golfers wanted to play, and the owner wanted to accept their money. Let's say for each of those 73 days with frozen or frosted turf, we did not allow the golfers to play for 2 hours in the morning. That's 2 hours of tee times off 2 tees, on 7 minute intervals, which comes to 137 golfers. Let's say the green fee was 12,000 yen. And let's lose those customers for 73 days. 137 times 12,000 times 73 = 120,000,000 yen. That's about a million USD. The only days we had to close were when we could not clear the snow. But we were trying everything possible to clear it. That's some serious money.



So how about the grass? How much damage was there? On the tees and fairways, the damage was negligible. Of course traffic on slow-growing turf is going to beat it up a little bit. I did not notice that the traffic on frost or frozen ground added to that.

On the greens I was really worried. Courses with more staff would typically put covers out on the greens, at least over the area where the day's hole location would be. We did that as much as we could, but we could not cover all the greens, or even cover all of a single green, with the limited covers and staff that we had.

I've looked through old photos. This is the worst spot on the practice putting green in January. The putting green got a lot of traffic every morning. Pretty ugly.


This, in February, is the worst spot on the 11th green, which was shaded until mid-morning in winter.


That was as bad as it got. By March, even though frosts were still happening, the grass filled in. The damage had not been nearly as bad as I'd expected.


In fact, the greens were cored on March 27. But winter still wasn't over.



By April, there wasn't a hint of damage from all the traffic. No grass was dead, any thin spots were gone, and the grass was growing like crazy.



I'm not sure there's a moral to this story, other than one must do what is in the best interest of the facility. In the case of Habu CC that winter, it was best to have customers playing the golf course.

Fall potassium and winter traffic on a bentgrass green


I just finished reading Winston Mirmow's thesis on Fall potassium fertilization and winter traffic effects on a creeping bentgrass putting green. I downloaded this in September and read the abstract then, but only read the full thesis now.

As I've mentioned previously, I like reading theses, because they are the most recent research results presented in a detailed format. I can learn new things and correct my thinking if I've been in error about something. I really enjoyed this one. It was about two of my favorite topics: potassium (K) and winter traffic.

The thesis

You can read the thesis yourself if you like. Here are the three things I found most interesting.

First, the fertilizer. Adding supplemental K in the autumn had no effect on traffic damage over frozen turf in the winter. Where no K was added was the same as where K was added. The low rate was 0 K, and the high rate was 7.3 g K/m2 (1.5 lbs K/1000 ft2).

Second, traffic was applied at 8 a.m. to the creeping bentgrass green when the canopy temperature was below freezing. That worked out to be 19 traffic events in the first winter of the study, and 18 traffic events in the second winter of the study. Yes, traffic decreased the turfgrass quality. The trafficked turf was worse than the untrafficked turf from January 15 until March 15.

But guess what? The untrafficked turf in mid-winter was rated at less than acceptable quality too, from February 1 to March 15. The trafficked turf was worse, and the untrafficked turf wasn't very good either.

And then when the temperatures warmed up in the spring? "When the weather warmed to the point where no more traffic treatments were applied, there were no significant differences in turfgrass quality ratings." That is, by April 1, all the plots were the same, whether they had been protected from traffic when frozen, or whether they had received 8 a.m. traffic over frozen turf.

Third, the soil K was below the MLSN guideline and the grass did not respond to K fertilizer. That's not at all what this experiment was about, but it shows something that I often explain, and will do so here again.

Even though the MLSN guidelines are lower than conventional soil nutrient guidelines, they are still set to be conservative. By that I mean the quantity of fertilizer recommended when using the MLSN guidelines is deliberately meant to err in one direction -- on the side of too much fertilizer, rather than too little. Of course the MLSN approach will in most cases recommend less fertilizer than will conventional guidelines, but at the same time there is a built in margin of error to make sure there is no deficiency.

Results like those presented by Mirmow, where the soil is below the MLSN level (Mirmow's results, converted to Mehlich 3 units, had values in the 20 to 30 ppm range), but the grass does not respond to applications of the element, indicate that the element was not deficient. Thus, more confidence that the MLSN guidelines are conservative.

Winter traffic on bentgrass

I used to be horrified of traffic on frozen bentgrass. I still kind of am, but I have also seen all kinds of traffic on frosted or frozen or snow-covered bentgrass.


And my observations of what happens are similar to Mirmow's research. The traffic makes the grass worse than where no traffic occurred, but in early spring everything is back to normal.

These are the practice greens at Habu CC near Tokyo in mid-March. This is after a winter of play on frosted greens, of snow removal by any means possible so that golf could be played, and by mid-March these greens were already recovered from the damage.


A request to authors

I was pleasantly surprised to see the soil test and tissue test data shared in their entirety in this thesis. That's great.

However, for the soil test data, the methods section doesn't give the sampling depth. And the methods section only says which lab the analyses were conducted at, but not which testing method was performed. Because both the sampling depth and the testing method affect the soil test data, authors of technical papers should include that information. I looked up the lab in this case, and can infer that the test was Mehlich 1.

I've reviewed a paper recently with the same issues. Essentially, it said soil samples were sent to X lab for analysis and the results are in Table Y. That's fine, but one can't understand the numbers unless some details of the analysis are given.

Applying the grammar of greenkeeping

Over the past two weeks, I've had multiple conversations about the way I think of turfgrass management. It all starts with a definition of greenkeeping as managing the growth rate of the grass. I wrote about this in A Short Grammar of Greenkeeping. You can get your copy here.

Application of the grammar allows for easy communication among turfgrass managers about the work they are doing. I'll use the creeping bentgrass greens at Hazeltine National GC as an example. Volunteers from near and far were at Hazeltine during the Ryder Cup.

Let's say that I was from Madrid, or San Francisco, or Sydney, and I wanted to get green conditions that were more like those at Hazeltine. One of the ways I would try to do that would be to apply a similar quantity of nitrogen. But how to compare locations?

I would use the temperature-based growth potential (GP). For Minneapolis, the GP looks like this.


If I set the maximum monthly N at 3 g/m2, and multiply by the GP, I get a maximum annual N of 13.3 g/m2 for that location (Minneapolis). Now I'll make up a number, because I don't know exactly what it is, but let's say the actual quantity of N applied at Hazeltine was 9 g/m2.

I'll use the log percentage (L%) difference for consistency. The L% is the natural logarithm of the ratio of two numbers, multiplied by 100:

If 9 g N were applied at Hazeltine, and the value calculated using GP as described above is 13.3 g, that is a 39 L% reduction.

If I want to apply proportionally the same amount of N at another location, I can calculate the GP amount, which I'll call a standard value, and then take a 39 L% reduction.


The standard using these calculations comes to 16.7 g at Madrid, 20.1 at San Francisco, and 28.9 at Sydney. Knowing that there was a 39 L% reduction at Hazeltine, my starting point for Madrid, after applying the same reduction, would be 11.3 g N/m2. At San Francisco, the N would go from the standard calculation of 20.1 down to 13.6 g, and at Sydney the 39 L% reduction takes N from 28.9 to 19.6.

This grammar facilitates the rapid sharing of relative inputs used to produce turf surfaces all over the world. Let's say we know there are amazing bentgrass greens in Sydney with N inputs of 10 g/m2/year. A corresponding quantity of N in Minneapolis would be 4.6 g.

This same approach can be applied for the quantity of water supplied in comparison to evapotranspiration (ET), to frequency of mowing, to evaluation of the growth rate, to assessment of the photosynthetic light, and so on. I find this approach quite useful in rapid implementation of maintenance practices that work well at location A, applied to location B. One then has a site specific starting point that can be further adjusted at location B, based on turfgrass response at that location.

Another interesting technique to modify fairway conditions

I've seen introduction of seashore paspalum to bermudagrass, and manilagrass to bermudagrass, by hand planting the introduced species into slices cut into the exisiting turf. This post shows seashore paspalum planted into a bermudagrass fairway using that technique.

I've also seen resodding to convert to a different grass, but in a way that doesn't require course closure.

At PGA Catalunya, hybrid bermudagrass was introduced into the creeping bentgrass fairways. These photos show the fairways in 2016, five years after the bermudagrass was added.


The idea was to improve fairway conditions in summer with the bermudagrass, due to the poor irrigation water quality. I've been impressed with the fairway conditions at PGA Catalunya, and also with the technique used to introduce the bermuagrass. These videos of the technique are shared on course superintendent David Bataller's YouTube page.


What technique was used at PGA Catalunya?

First, simulated divots were made in the bentgrass fairways using an aerifier fitted with custom "tines".

Second, a rotovator or landscape tiller was used to make a divot mix from certified Tifway 419 sod and sand.

Third, the divots in the bentgrass fairways were filled with the bermudagrass divot mix.

The result is improved fairway performance during the summer, due to the presence of bermudagrass. And with this technique, the improvement was accomplished rapidly, without closing the course, and used a relatively small amount of purchased sod.


Every spring when the snow melts ...

I look forward to some photos from Doug Soldat. For the past three years, he's had some fascinating photos to share of snow mold on creeping bentgrass. And each year, there was more snow mold where potassium fertilizer was applied, and less snow mold where potassium wasn't applied.

Spring of 2014

In the spring of 2014, there was more snow mold where K was applied.

Spring of 2015

Last year, there was also more snow mold where K was applied.

Spring of 2016

This year, it happened again. There was more snow mold where K was applied.

Doug will be talking about K in a TurfNet webinar in April: Is Your Potassium Program Hurting or Helping Your Turf?

On those creeping bentgrass plots in Wisconsin, adding K increases snow mold. No K had less snow mold.

At Rutgers, annual bluegrass plots deficient in K have had more anthracnose in summer and more winter injury. Eliminating the deficiency reduced those problems.

Then there is the MLSN guideline for K of 37 ppm. I recommend keeping the soil K above 37 ppm (Mehlich 3 extractant).

And there are hundreds of other studies about K. Some show a benefit from adding K, and some don't. I haven't read all of them, but I have read a lot of them. This sounds like it could be pretty complicated.

Actually, I don't think it is. Here's what seems to be the case, for both warm-season and cool-season grasses:

Ensuring the grass is supplied with all the K it can use will provide all the benefits associated with K. Adding more than that usually has no effect, other than wasting time and money, but sometimes has a negative effect.

As a turfgrass manager, all one has to do is ensure the grass is supplied with all the K it can use. This can be accomplished in 2 ways. One is by keeping the soil K above the MLSN guideline. A second is by applying N:K in a 2:1 ratio for cool-season grasses, a 1:1 ratio for seashore paspalum, and a 3:2 ratio for other warm-season grasses. I wrote about that in the final chapter of A Short Grammar of Greenkeeping and in The (New) Fundamentals of Turfgrass Nutrition.

Note that I do not recommend tissue testing for K (or any other element).

If you want to read more about K specifically, and about how the benefits of K come from correcting a deficiency, I recommend: