This is a lot to fit into an hour

But I am going to try. I've got four things I want to explain in this upcoming webinar, and I have made some interesting calculations. Can calculations be provocative? Maybe these ones are provocative and interesting.

The Campus del Césped webinar is on 12 January at 17:00 Central European Time. You can register here.

Here is the 4 page pdf handout, in English.


These are the slides in English.

These are the slides in Spanish.

If you are are joining this webinar, you will find it useful to review the slides and handout prior to the event.

Why I don't worry about micronutrients

This is nothing new. We've been discussing this for a long time. But these charts are new. I am leading a webinar on January 12 and in my preparations for that I made these charts.

I wanted to explain why I don't worry about micronutrients.

I'm going to explain this in words first, and show the charts at the very end. There are two main reasons why I don't worry about micronutrients.

First, the quantity of micronutrients used by the grass, when compared to the amounts of N, K, P, Ca, Mg, and S, is indistinguishable from zero. The grass uses micronutrients in such tiny amounts that it seems the grass can surely get such tiny amounts from the soil.

Second, and this is connected to the first reason, the quantity of micronutrients used by the grass is almost nothing. So there is no excuse for having a deficiency of any micronutrient, because even to apply two or three times as much micronutrients as the grass can use will cost essentially nothing.

Take those two reasons together, and you can't lose. You will probably never have a micronutrient deficiency, And you can spend almost nothing and be sure to prevent one.  Sounds easy to me. Which is why I don't worry about it.

Here are three charts to demonstrate what I mean.

First, this is the concentration of elements in turfgrass leaves. You'll notice that the concentration of micronutrients in leaves is indistinguishable from 0.


That's reassuring. The soil can probably supply almost all that the grass can use. But what if the soil can't supply that much?

No problem! The amount the grass uses is so small, it costs almost nothing to supply it.

If you have a 50,000 dollar fertilizer budget, and if all the elements cost the same, you would spend less than 60 dollars for each of the micronutrients. So if the amount used by the grass is so low, it seems easy to apply that much, and to afford that much, as fertilizer.


Of course not everyone has a 50,000 dollar fertilizer budget. What if your fertilizer budget is 700 dollars? Well, the grass won't distinguish between budgets, but it will still use nutrients in the same proportions. In this case, for a 700 dollar fertilizer budget, each of the micronutrients comes in at less than $1.

I hope this makes it clear why I don't worry much about micronutrients. You will probably not be deficient. But if you are worried about it, apply them. It will cost almost nothing.


Of course, if you are spending a lot of money on micronutrients, or are supplying a lot more than the grass can use, it would be prudent to ask yourself "What am I trying to do?"


This was a new one to me. I saw the course laid out at the Ayutthaya Historical Park and thought it looked similar to Park Golf. But where Park Golf involves hitting the ball into a hole, a woodball hole is completed when the ball passes through a gate.

Woodball course laid out on *Polytrias indica* in Ayuddhaya

A photo posted by Micah Woods (@asianturfgrass) on

This video explains the woodball rules.

Looks like fun.

Monthly Turfgrass Roundup: December 2016

Some great articles and summaries come out at the end of every year. Here are some excellent items from the past month:

Bill Kreuser learned these five things about PGRs this year.

Luke Partridge with photos from Emirates GC:

And Craig Haldane with more at the end of the week:

This is how to lose a lot of money with frost delays.

Brad Revill started a new blog with this widely-read post about something new.

I wish everyone understood this about the quantity of fertilizer recommended by the MLSN guidelines.

Soil tests double MLSN and still getting recommendations to apply more.

Do those who soil test also apply more fertilizer?

Ken Mangum on how green speeds have changed since 1978:

Intriguing article about expectations for greens at the Masters in 1981.

Radko et al. from the GSR in 1981: A study of putting green variability.

An unlikely tool for the study of putting green speed variability.

This eclectic list of references for my 芝草科学とグリーンキーピング book.

Hong Kong GC was looking (and playing) great during the HK Open:

What do Hong Kong, Singapore, Iceland, and Mauritius have in common?

The number of golf holes in 30 countries.

I came across an amazing video of Victoria GC in 1967:

J. Paul Robertson and Sean Parker with this photo of Victoria GC under snow:

David Duke wrote about winter damage to golf turf.

Idris Evans showed some well-trained kikuyugrass:

I made a map to show all the flights I took this year, with some grass photos too.

You won't see this every day:

Elephant footprints on a golf course in Thailand.

These 10 posts from 2016 had the most views on the Viridescent blog this year.

And this is the opposite! These 10 posts had the fewest views this year.

For more about turfgrass management, browse articles available for download on the ATC Turfgrass Information page, subscribe to this blog by e-mail or with an RSS reader - I use Feedly, or follow asianturfgrass on Twitter. Link and article roundups from previous months are here.

Sand, leading to more growth, needing more sand, leading to more growth, needing more sand

Frank Rossi and Dan Dinelli had an interesting conversation on Turfnet Radio. I learned a few things, and I even agree with some of what they discussed. But not all of it.

The first thing that came to mind when I heard them talking about sand and growth was lawns beside the ocean. More about that later.

If you jump to the 30:40 mark of the podcast, Dinelli says, "I'm convinced that the more sand we put down, the more biomass, the more organic matter we develop. And I know that is counterintuitive."

It sure is. Because I'm thinking of a lawn next to a beach, where windblown sand just keeps coming and coming. Or I'm thinking of the 7th hole at Sandpines in Florence, OR.

In the situation I'm thinking of, the sand is not a cause for organic matter development. Back to the podcast.

When asked about this, Rossi took his turn as the guest and answered that he would say there are two components to it. First, there may be nutrient or PGR programs that need to be addressed.

Then he said this about the bigger question on it:

"When you aggressively verticut you thin that stand and then you incorporate sand into it and I believe that leads to even more biomass production and that's the chasing the tail part ... you have to thin it out .. to make room for the sand, but by doing that, aren't you stimulating more growth?"

I don't think that's how it works. If it is, sand isn't the cause of it. And I don't think verticutting is either. Growth is affected by temperature, and light, and nitrogen, and water. Those are the primary things that influence it. Put simply, more of them and there will be more growth. Less of them, and there will be less growth.

So let's go back to the beach. Or to a lawn beside a sand dune. Let's hold N constant. We'll provide whatever you consider a miniscule N rate to our beachside or duneside lawn. We'll need to make sure the grass has enough water. Let's make sure the soil is kept just above the wilting point. The grass won't wilt, but that's all the water that is supplied. And let's set the temperature to be optimum for growth, and we'll make the light optimum too.

Now let's divide the lawn into three parts. One part has sand restricted from blowing across it. With that N rate and irrigation rate, do you expect a lot of biomass production? I don't.

But I'm pretty sure that part of the lawn protected from topdressing is going to have more biomass production than the second part of the lawn, where I allow sand from the beach (disregard any salt effects here, and just consider sand) or adjacent dune to blow across at topdressing rates throughout the season, depositing let's say 1.2 cm of sand over the course of the season. Remember, we are growing this grass with a miniscule N rate and irrigation just to keep the soil above the wilting point.

I think the section of my lawn where I restrict the sand completely is going to develop more organic matter. And then there is the third section of my lawn, where I don't restrict the sand at all. In that case I have a dune at the end of the season and the grass is dead, producing no organic matter at all.

If verticutting and sand topdressing are producing too much organic matter, please consider what would happen if you continued to verticut and sand topdress while stopping all fertilizer and all irrigation. The organic matter production would stop, because the grass would die.

Here's the kind of situation I'm thinking of. These are all manilagrass (Zoysia matrella). Some people think of this species as having heavy thatch.

image from

image from

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Plant it beside a beach, give it a very slow growth rate, and then add sand, and you get no thatch at all. You do get something that would probably be a better turf if less sand were added to it.

Isn't the growth rate largely a fertilizer (especially N) and a water issue? I don't see how sand and verticutting cause the grass to grow more.

"Maybe those that soil test are just more likely to fertilize in general?"

Ryan Goss made a good point in the discussion about how much fertilizer is applied on golf courses. Original blog post here.

There are two basic scenarios.

The first scenario is no soil testing, in which it makes sense to apply the same amount of fertilizer, F, as the grass can use, G. One doesn't know how much is in the soil, one can assume the soil will supply nothing, and as an equation this can be represented as F = G. Maybe add just a little more to be sure. Call it F = G + 10%. I'd think of this as a hydroponic situation, where the soil can supply nothing.

The second scenario is with soil testing. In this case, the amount of fertilizer to apply should be the amount that the grass will use that cannot be supplied by the soil, S. Any amount that is supplied from the soil is not required as fertilizer. In this scenario using soil testing to find what the soil can supply, the amount to apply as fertilizer becomes F = G - S. Maybe add just a little more to be sure. Call it F = G - S + 10%. If the soil can supply nothing, then S is 0 and the equation simplifies to the "hydroponic" situation described in the first scenario.

With these simple equations, it is apparent that the amount of fertilizer to apply, represented as the value F, will always be lower in the second scenario, with soil testing.

Ryan is right that those who soil test are probably more likely to fertilize in general. But there is something interesting if we look at the data in Table 7 from Gelernter et al. (2016). Phosphorus and potassium are often recommended based on soil tests, but turfgrass nitrogen rates are not based on soil tests. Therefore, I'm going to use the amount of N applied as a baseline estimate of how much more likely soil testers are to fertilize than non-testers.

I use the log percentage (L%) to show the relative changes. More about log percentage at the end.


I took the average L% increase across all areas of the golf course for each nutrient. A typical 18 hole golf course that soil tests will have an 18 L% increase in nitrogen rate compared to a typical golf course that doesn't soil test. Because nitrogen is not based on soil tests, I'll pick that number and say that the overall increase in fertilizer from those who soil test is likely to be 18 L% more than those who don't soil test, just based on what Ryan pointed out.

Then I move to phosphorus and potassium and compare them to the 18 L%. Phosphorus and potassium recommendations are based on soil tests, so if they increase by about 18 L% too, then we can't say soil tests have anything to do with it. Phosphorus fertilizer (shown as P2O5) was variable. The average was a 19 L% increase when soil testing, but there was a wide uncertainty interval around that estimate.

Potassium had an average increase of 39 L%. Even if the typical golf course that soil tests is already likely to apply 18 L% more fertilizer in general, that baseline increase does not explain the 39 L% increase in potassium fertilizer.

Why log percentage (L%)? This is described in Törnqvist et al. (1985) as "the only symmetric, additive, and normed indicator of relative change."

I didn't want to compare the absolute amounts of N, P, and K applied, because it is normal that one will apply more N than K, and more K than P. Saying the soil testing sites used half a pound more N (it was 0.4875 lbs more, to be exact) than the sites that didn't soil test is fine. Then I can also say that the soil testing sites used 0.16 pounds more P2O5 than did the sites that didn't soil test. Both those statements are correct. But that's not exactly what I want to compare. I don't want the absolute difference. I can't compare the half pound of N to the 0.16 pound of P. What I'm interested in is the relative change.

I could use the usual percentage, but that has problems too. The sites that soil tested used 3 lbs of N on average. 3/2.5 = 1.2. 3 is 120% more than 2.5. A 20% increase. So is that also a 20% decrease? 20% of 3 is 0.6. That's not symmetric. And 2.5/3 = 0.833. So is it a 17% decrease then? Or a 17% increase? It is confusing.

The log percentage solves this. ln(3/2.5) = 0.182. An 18.2 L% increase. ln(2.5/3) = -0.182. An 18.2 L% decrease. Very convenient.

Top 10 posts of 2016

These ten posts from 2016 had the most pageviews. Here they are, counting down from the tenth to the most viewed post. And I'm including a pretty photo of Mt. Fuji just for fun.


[10] November, Both of these are worth your time about organic matter management, and coring greens, or not.

[9] May, Roots, growth potential, and fertilizer discussing what was applied to putting greens in New Delhi.

[8] April, Is this the most common oxymoron in turf? about a question that just won't go away. Can nutrients be adequate but not available?

[7] November, Fall potassium and winter traffic on a bentgrass green about the remarkable tolerance of creeping bentgrass to traffic when frozen.

[6] October, Daily versus monthly calculations of ET and irrigation requirement in which I show that a daily soil water balance gives a totally different irrigation requirement than does a monthly calculation using the standard method.

[5] February, Which products and technologies are truly beneficial and cost-effective? is a quote from Dr. Carrow's Green Section Record article on Purchasing new products and technologies: an ethical and common-sense approach. He explains why this is an ethical issue, and gives 7 questions to ask about products and technologies.

[4] January, Knowing which soil test results are important can simplify turf management. That's a quote from Bill Kreuser; he says that "while soil tests can be useful, their results are frequently overanalyzed and overinterpreted."

[3] September, Fast release fertilizer, fertilizer burn, and root growth in which those topics were mentioned.

[2] November, High expectations, about the energy use and greenhouse gas emissions from golf courses.

[1] May, Data to support an anecdote about decreasing organic matter in the top 10 cm of putting greens with minimal coring or topdressing.

Thanks for reading!

Lists of the most popular posts from previous years are here:

  • Top 10 posts of 2015 about fertilizer, green speed, soil tests, wind at St. Andrews, the 1/3 rule of mowing, U.S. Open at Chambers Bay, and foliar applications.
  • Top 10 posts of 2014 about seasonal N use, control of turf diseases, an anecdote about ammonium sulfate, salesmen suggesting calcium, cool-season grass in the tropics, irrigation, and soil moisture.
  • Top 5 posts of 2013 about summertime syringing to cool bentgrass, nutrient requirements, and potassium.
  • Top 5 posts of 2012 about five articles every greenkeeper should read, 1 minute on fertilizer, the real price of fertilizer, and the imaginary problem of calcium deficiency.
  • Top 5 posts of 2011 about modifying fairway conditions in Thailand, sandcapping or topdressing, weeds in Malaysia, and turfgrass potassium requirements.
  • Top 5 posts of 2010 about zoysiagrass fertilizer, the China Golf Show, grass selection and manilagrass, Guidelines for Tropical Turfgrass Installation and Management, and turfgrass performance data at the Open Championship.
  • Top 5 posts of 2009 about mowing patterns and grass color, core aeration, salt for weed control, seeded seashore paspalum, and turfgrass in Dubai.

Map of all the flights I took in 2016

I took 82 flights this year, for a total of 221,494 km (137,000 miles), and I've just mapped them. That's more than 5 times the circumference of the earth. Routes flown once are more blue, and the routes flown more often are more red.


That's more flights and more km than in 2015, when I flew 54 times for 186,056 km. A map of 2015 flights is here. It's been another extraordinary year for studying grass around the world.

Festuca and Agrostis in Washington


Native grasses at BKK when it hasn't rained for months


Organic matter accumulation from Zoysia japonica above a sand rootzone in Japan


Creeping bentgrass practice green with lots of target flags in Girona


Puccinellia maritima (I think that's the species) near Reykjavik


Poa pratensis at Kashima Soccer Stadium


Zoysia japonica and Zoysia matrella in Japan


Fine fescue in Nebraska


A rare first edition of Short Grammar of Greenkeeping in Kyoto


If you want to see more photos, have a look at the ATC photos on Flickr, or scroll through the @asianturfgrass media tweets.

The soil test numbers are almost double MLSN standards and I'm still getting recommendations to apply more

That arrived in my inbox recently, plus a few questions about calculating K requirements using the MLSN guidelines, and whether if there are minimum levels, are there optimum levels too? Here's how I answered.

It sounds like you are on the right track. Here's a few general remarks based on what you described/asked:

If the lowest K on that course's greens is 57 ppm, you are great. You are mostly Poa on those greens, right? The grass will use about twice as much N as it does K. Therefore, my suggestion is to apply half as much K as you do N, and that should keep the soil at about that level well above MLSN. Check a year later and see if the trend is going up or down. If going up, you can cut the fertilizer, and if going down you might increase it. What you are basically doing is applying 100% of what the grass is using plus you are keeping a nice reserve in the soil. That is a safe way to do it and it is not gratuitous overapplication.

For the other courses, it makes sense to let the numbers get a little closer to the MLSN minimum. I would make the calculation based on the soil test and the expected N application rate. The 22 ppm change in soil concentration is correct for a pound, if you are thinking of a 6 inch deep rootzone. For putting greens -- actually for most mowed turf in general -- I think of the rootzone as being 4 inches. In that case you can expect a pound of application per 1000 ft2 to increase the soil by 33 ppm. You can expect the harvest of a pound per 1000 by the grass to reduce the soil by 33 ppm.

If you apply 4 pounds N, expect the grass to harvest about 2 pounds K (50% K use compared to N). MLSN at 37 ppm is about 1 pound of K. That's always going to be there in reserve; we don't want the soil to drop below that. If you have a soil test at 45 ppm, then the way to calculate a fertilizer requirement is like this.

Amount needed is amount to keep in reserve (the MLSN minimum) plus the amount the grass will use minus the amount actually present. I'm going to say you calculate this for a 4 inch rootzone depth and you will apply 4 pounds of N.

That is 2 lbs of K use + about 1 lb K needed as the MLSN minimum - (45/37 = 1.2 lb in the soil now). That is 3 - 1.2 = 1.8 pounds of K required to keep the grass from dropping below the MLSN guideline. I suggest dividing that 1.8 pounds (your number is going to be different, I am just showing how I make the calculation) into as many apps as possible and then applying it through the season. Or, if you are applying 4 pounds N, then you have a 4 to 1.8 ratio of N to K, and just apply close to that ratio at every application.

It can be simpler than that, but that is the detailed work through of the calculations. The really simple way is if the soil is less than 50 ppm, apply N and K in a 1:1 ratio. That is bound to make the soil K go up, so you will be sure to be staying above MLSN. If the soil is in the 50 to 75 ppm range, apply 2:1, and that should keep the soil at a similar level. When the soil is above 75 ppm, so long as you aren't applying a ton of N, you probably can get by with little or no K.

I prefer to make the exact calculation. And then check the grass response to the fertilizer and adjust inputs accordingly.

Oh, is there an optimum? I don't think there is. I think there are problems if you get too low with any element, but once you move from "too low" to "enough", then all the benefits from that element have happened. The MLSN approach is designed to prevent you from getting "too low" and to make sure you are always in the "enough" range. Once there is enough, the problems are expected to be from traffic, or dry spots, or shade, or whatever. The idea with MLSN is to provide a framework to put every element in the "enough" range and then you can focus your limited time and energy on the other things that might be affecting turfgrass performance.