Both of these are worth your time

One is an article, another is a podcast, and you won't regret the time spent reading the first and listening to the second.

First, the 4 November issue of the Green Section Record contains Managing Organic Matter in Putting Greens by Adam Moeller and Todd Lowe.

This article explains that "there are many agronomic programs that influence the playability and health of putting greens, but organic matter management is arguably the most important." It goes on to explain the standard practices in 2016.

Moeller and Lowe conclude that "traditional programs", and by that they mean programs that include core aeration, "still provide the most consistent results for managing organic matter and improving putting green conditions."

This is a really good article for referencing what is standard in 2016, but I'm not in full agreement with their conclusion. I used to think that coring was essential, but over the past few years I've changed my thinking. More about that in the footnote.

The second item is the recent TurfNet Radio podcast with Frank Rossi and Chris Tritabaugh about managing for the Ryder Cup. If you listen to this, you will find that they discuss organic matter on putting greens (and a lot of other interesting things), but if you haven't heard, there has been no core aeration on the greens at Hazeltine since 2013.

The article says coring provides the most consistent results, and the podcast explains how greens are managed to a high standard without coring. It's good to be informed about this topic, so that you can be sure to make the right choices for any turf that you manage.

Footnote: I used to recommend the removal of 20% of the putting green surface area by coring each year and the annual addition of at least 12 mm of sand topdressing. I don't make that recommendation anymore.

Rossi and Tritabaugh talked about the grass yield and growth rate. How much was the grass growing? The idea being that one can match the quantity of sand applied to the rate of grass growth, thus avoiding coring by maintaining a consistent organic matter content at the soil surface. But they did not put a number to the growth rate. I think it is possible to put a number to the growth, and from that to make a site specific plan for organic matter management.

Consider the "new" bentgrasses with high shoot density, or ultradwarf bermudagrasses, widely considered to be prolific thatch producers. Please consider now how much thatch bentgrass will produce in Bangkok, or how much organic matter Miniverde will produce in Moscow. None, right? Now please continue that thought experiment a step further, and consider how much thatch (or organic matter) grasses produce when they grow slowly, supplied with just enough nitrogen and just enough water to produce the desired growth rate. Supply no N and no H2O to ultradwarf bermudagrass and there won't be any organic matter to manage. Is it possible that there is a level of growth at which minimal topdressing and no coring produce the desired surface? That's the goal, and I think it is possible with careful attention to the growth rate.

And that avoids (or at least minimizes) the putting surface disruption associated with coring too.

For more about this, see:


Fast release fertilizer, fertilizer burn, and root growth

I gave a seminar in July in which I discussed how much one can expect grass to grow.

I said something like "grass can always grow more, but turfgrass managers restrict the growth rate by supplying less nitrogen fertilizer than the grass can use. For example, I could apply 100 g/m2 of 10-10-10, and the grass would grow more rapidly than if I applied only 10 g/m2."

Someone in the audience disagreed with me. "You can't apply 100 g/m2 of 10-10-10," he said. "That much will burn the grass."

I wondered about that, so I went shopping for 10-10-10. I didn't find a 10-10-10 with suitable particle size. The closest analysis with a particle size suitable for application to turfgrass was 14-14-14. I bought a bag.

Then I marked out plots on a korai (Zoysia matrella) nursery. Each plot was 1 m by 1 m, and there were seven plots in total.

This is what the plots looked like right after the fertilizer application, before turning on the irrigation, on 31 July 2016.


I had measured out the 14-14-14 fertilizer and applied it to these plots. One plot received no fertilizer, and the other plots had 14-14-14 applied at rates from 2.5 up to 15 g N/m2 in 2.5 g increments (that's an N rate of 0 to 3 lbs N/1000 ft2 in 0.5 pound increments).

This is what the plot receiving the 15 g N/m2 rate looked like after I spread the fertilizer and before irrigation was applied.


I wanted to check three things with these fertilizer treatments.

First, I wanted to see if this much fast release fertilizer would burn the grass. In the seminar, I'd said that 100 g/m2 of 10-10-10 could be applied, but no one would do that, because it would make the grass grow too fast. In this test with 14-14-14, I included N rates all the way up to 15 g/m2, equivalent to 150 g/m2 of 10-10-10.

Second, I wondered what would happen with root growth at different rates of fertilizer.

Third, I wondered how long a color or growth response would last. For example, when the grass starts going dormant in the autumn, would the effects of a 31 July fertilizer application still be visible?

Before I applied the fertilizer, the roots were like this. These roots are from the plot receiving the highest rate of 14-14-14, before any fertilizer was applied.


The fertilizer was watered in and there was no burn. Maybe just a little bit where a few particles didn't dissolve completely, but the overall effect was to make the grass greener. A week after the fertilizer application, the plots looked like this. In the foreground is the plot with no 14-14-14 applied, and each plot after that received an increasing 2.5 g N/m2 increment of 14-14-14.


This plot received 15 g N/m2. A week after the application, it was greener than the surrounding grass that didn't receive fertilizer. If there was any burn, one might pick out a few leaves here. They didn't last long.


 I came back a month later and had a look at the plots on 30 August.


I also looked at the roots for each of the fertilizer treatments. I had expected that adding some 14-14-14 would cause an increase in roots. All the plots showed an increase in roots by 30 August compared to the roots I looked at on 31 July. But I don't see any increase in roots with fertilizer application. If anything, the root system was largest in the control plot that received no fertilizer.


The soil on this nursery is similar to the soil on the course. The nursery soil wasn't tested, but the course soil was, and in May 2016 the median pH was 6.4. Using the Mehlich 3 extractant, the mean K, P, Ca, and Mg were 59, 172, 1304, and 57 ppm.

All these elements were present at adequate amounts in the soil, so adding more K and P in the 14-14-14 didn't make the roots grow more. I had expected more N (up to a point) would cause an increase in root growth, but after one month, that's not apparent at all.

MLSN and the probability of a response to fertilizer application

Travis Shaddox shared an impressive list of quotes about BCSR. Some key words from those quotes include irrelevant, inefficient, pseudoscience, should not be used, and NOT recommended.

Instead of BCSR, Allan Dewald asked about MLSN, and Travis mentioned that MLSN doesn't provide a response probability, but maybe that is coming.

We won't provide a response probability for MLSN because it is not a fertilizer calibration. These are two different things.

MLSN is a method for interpreting turfgrass soil test results, based on an analysis of thousands of soil samples in which turfgrass is producing a good surface. MLSN is developed from thousands of soil test results in which turfgrass performance was fine.

This is a paraphrase of what we wrote in the MLSN preprint:

Traditional soil test calibration for turfgrass is impossible and will never be done. It is impossible because turfgrass is a global crop, with many species and varieties used, in thousands of soil types, in every possible climate, across a range of turfgrass performance requirements. MLSN is a method which allows turf managers to ensure their turf is always supplied with enough nutrients.

For the full details of what MLSN is, and to see the data supporting it, please read the paper.

Now to elaborate on why I think probability of a fertilizer response is not the right way to do calibration for turfgrass, and why MLSN works even though it is not a traditional fertilizer calibration.

Calibration is based on classifying soils with different levels of nutrients into categories based on probability of yield response. For full details, see Chapter 14 by Douglas Beegle, Interpretation of Soil Testing Results, in Recommended Soil Testing Procedures for the Northeastern United States.

The classification into probability of response, according to Beegle, involves three categories. In the below optimum category, also called very low, low, or medium, "the nutrient is considered deficient and will probably limit crop yield. There is a high to moderate probability of an economic crop yield response to additions of the nutrient."

In the optimum category, also called sufficient or adequate, "the nutrient is considered adequate and will probably not limit crop growth. There is a low probability of an economic crop yield response to additions of the nutrient."

The third category is above optimum, also called high, very high, or excessive. In this category, "the nutrient is considered more than adequate and will not limit crop yield. There is a very low probability of an economic crop yield response to additions of the nutrient."

In turfgrass management, one is not trying to maximize economic crop yield. Rather, one is trying to produce the desired surface performance, and does that by modifying the growth rate of the grass.


I wrote about this in A Short Grammar of Greenkeeping.

When modifying the growth rate of the grass, one is often trying to minimize the growth rate. Let's try anyway to apply these probabilities of response to turfgrass.

If we take the categories for probability of response, as defined by Beegle, we notice that he has referred to crop yield and to an economic crop yield response. Let's drop that and substitute turfgrass performance and turfgrass performance response. Now we have a definition that makes sense for turfgrass.

Below optimum: The nutrient is considered deficient and will probably limit turfgrass performance. There is a high to moderate probability of a turfgrass performance response to additions of the nutrient.

Optimum: The nutrient is considered adequate and will probably not limit turfgrass performance. There is a low probability of a turfgrass performance response to additions of the nutrient.

Above optimum: The nutrient is considered more than adequate and will not limit turfgrass performance. There is a very low probability of a turfgrass performance response to additions of the nutrient.

I think it is impossible to do soil test calibrations for every grass, climate, soil, and turfgrass use combination. So how can we figure out some way to interpret turfgrass soil tests and assign the results into one of those three categories? That's where MLSN comes in.

What we did with MLSN was look at thousands of soil test results from the optimum and above optimum categories. The turf was performing well at the time the sample was collected, so the soil was unlikely to be in the below optimum category.

Then we studied the distribution of the nutrient levels in those soils, threw away the bottom 10% to make sure we have some buffer against being too low, and identified the MLSN guideline as the level in the soil that we don't want to drop below. Nutrient recommendations are then made to ensure the soil doesn't drop below that minimum.

Because the soils used to identify the MLSN guidelines were already in the optimum or above optimum category, there is an implied probability in the MLSN recommendations. That is, keeping the soil from dropping below the MLSN guideline is the same as keeping the soil at a level with a low to very low probability of a turfgrass performance response to additions of the nutrient.

Although such probabilities are implicit in the MLSN approach, we do not use those terms or classify soils into categories. With MLSN, we have just two categories -- enough, and not enough. Turfgrass is a perennial crop, and soil nutrient levels go down as the turf harvests nutrients from the soil. The MLSN fertilizer recommendations consider how much of an element is in the soil now, how much of that element the grass will use over time, and then makes a recommendation to provide enough of that element to meet all the grass requirements.

Soil temperature and fairway management from 1980

I don't recall what I was searching for, but I stumbled fortuitously across this article by Oscar Miles from the Green Section Record in 1980:

Soil temperature and related fairway management practices -- northern turfgrasses

It's a great read, and quite interesting to see how he anticipated so much of the maintenance as conducted today.

"The additional data, I believe, will help us set up a program that a data processor or computer can maintain for us. I feel it is inevitable that mini-computers will make their way into golf course management systems. This is not as far-fetched as you might think."


p.s. Now I recall. I probably was searching for something related to soil water content and nighttime soil temperatures in summer.

A little more data to support an anecdote

Yesterday I wrote about soil organic matter decreasing over a 3 year period, even though the greens had only been cored twice in that time, and sand topdressing amounts had been reduced each year.

17th green after coring in May 2013

When I think about reducing organic matter, I usually think of removal or dilution. Removal would be through coring or scarification; dilution would be by mixing sand with the organic matter.

12th green after 12 mm core aerification and topdressing in May 2013

But in this case, I think the organic matter in the soil is going down because the organic matter production is less than the organic matter decomposition. The reason I think this is simple. There hasn't been much removal or dilution of organic matter in the past 3 years, but the organic matter has still gone down.

The 14th green in August 2013

In the comments to yesterday's post, there was some discussion of layering if sand was not applied often enough. I agree that undesirable layering might occur, but only if the grass was producing organic matter faster than it was decomposing.

To put this into context, I added up the volume of clippings from the greens in 2015, to give some idea of the growth rate at which the maintenance work described yesterday has led to a decrease in soil organic matter.


Add that up for the year and it is 270 L/100 m2. Measurements of the fresh weight of clippings on these greens give 0.3165 kg for each liter of clippings, so that is 85 kg of fresh clippings per 100 m2. I expect these clippings are about 70% water and 30% dry matter, so I've estimated the dry weight of the clippings at 26 kg/100 m2.

That gives three estimates of how much the grass is growing at this location. Those numbers might be useful if you'd like to compare the growth of grass where you are.

As an aside, these types of calculations are how I estimate nutrient harvest. If you've been to one of my seminars about how to use the MLSN guidelines, I will have described that the use of the guidelines involves taking the amount the grass will use (I'll call that a), adding that to the amount I want to make sure remains in the soil, which is the MLSN guideline (I'll call that b). These values a and b, together, are the amount of an element we want to be sure is present. a + b represent the amount we want to have. The amount we actually have is measured by the soil test, and I call that c. It follows that the amount of an element required as fertilizer is the amount we want to have, minus the amount we do have, represented in an equation as a + b - c.

Data to support an anecdote

Last week I received the latest soil tests from Keya Golf Club, where Andrew McDaniel is the superintendent. I'm sharing the organic matter results from the greens, because I think they will be of general interest. This chart shows the soil organic matter % on the greens for samples taken in early 2013, 2014, 2015, and now 2016.


Now for a bit of a tangent, and then back to the work that's been done at Keya since 2013. It would seem that not core aerifying, and not topdressing all the time, would be considered alternative maintenance. Another way to look at it is that the management of soil organic matter -- the amount of work required in that regard -- will be proportional to the growth of the grass.

I remember a conversation I had once during break time at a seminar in New Delhi. "Tifeagle and other ultradwarf bermudagrass varieties accumulate too much thatch," someone told me, "and will require almost constant and aggressive verticutting to keep it under control." I disagreed, pointing out that the amount of thatch (organic matter) control required will be related to how much the grass grows. "Tifeagle in Siberia won't produce any thatch at all," I said.

As an example, this is Zoysia japonica in late July in Yorkshire, surrounded by cool-season grasses. The zoysia is not producing much organic matter at all, and there's no need to verticut or topdress or core.


Another example: this is Penncross in Thailand. It germinates, but doesn't require mowing. If you can keep it alive, you certainly don't have to worry about organic matter management.


Rather than prescriptive recommendations of surface area to be removed by coring (I've recommended this in the past) or the quantities of sand that should be applied as topdressing (I've also recommended this in the past), I now think it is more reasonable to consider the growth rate of the grass, and to manage the organic matter as required based on the growth rate.

Ideally, there will be no coring, minimal verticutting, and minimal topdressing. That's easier, and it causes less disruption to the playing surface. Such an approach may not be possible, but I prefer to have my ideal as great surfaces all the time, with minimal disruption, compared to the alternative ideal of great surfaces except when coring to remove x % of the surface area each year while applying a total of y mm of sand per year.

Back from that tangent to the greens at Keya, where the organic matter on greens has been going down since 2013.


If one does a regression on these data, for each day that passes, the organic matter in the top 10 cm of the soil has gone down by 0.005 g per kg. In 365 days, the reduction is about 1.8 g/kg.

Here's where the data support an anecdote. The anecdote is, managing the growth rate allows one to minimize or eliminate coring.

The N rate on these greens in 2013, 2014, and 2015, respectively, has been 14.6, 9.5, and 10.6 g/m2. That is still enough to produce a dense korai turf (manilagrass or Zoysia matrella).


Coring and solid-tine aerification has been minimal and has decreased while the greens have only improved. 12 mm core in May 2013, 12 mm solid in July 2013, 12 mm core in June 2014, and 13 mm solid cross tine in July 2015. That's not much, and the organic matter is going down.


Greens were verticut 3 times in 2013, 3 times in 2014,and 4 times in 2015.

Topdressing amounts have been 8 mm in 2013, 4.6 mm in 2014, and 3.8 mm in 2015.

You see the trend? Core aerification is done infrequently, sand topdressing is applied less and less, N fertilizer is applied at a reasonable rate, and the soil organic matter goes down. It's a viciously good cycle.

How to save 82% on fertilizer cost

There is another good article in the Green Section Record, this one by Blake Meentemeyer and Brian Whitlark on Turfgrass Fertilization. You'll want to read the full article. It talks about the overall goals of fertilizer application, soil tests, some myth busting, fertilizer and playability, and more. It's a modern article with a lot of historical references too.

The most interesting part of the article for me was the economic case study. A course reduced the putting green fertilizer cost by 82% and the result was "the putting greens have never been healthier."

For more about this topic, see How to save 60% or more in turfgrass fertilizer cost.

Roots, growth potential, and fertilizer

Last month Bhupendra Singh shared this photo of roots on a Tifdwarf putting green in New Delhi.


Growing roots! Tifdwarf at Peacock Course Greens, Delhi Golf Club.

A photo posted by Bhupendra Singh ( on

I wondered how the grass had been managed for the past six months.

Here's the high and low temperatures in New Delhi from November 1 until April 9. Delhi_temperatures
Those temperatures, converted to a C4 growth potential (GP), show that the GP was low in winter and approached a maximum as the temperatures warmed in the spring. Delhi_gp
So was there anything extraordinary done to develop roots like this?

Bhupendra informs me (and sent along those photos to confirm the results) that the N sources have been ammonium sulfate, urea, and potassium nitrate. The P source is single super phosphate, and the K has come from potassium nitrate and potassium sulfate.

The application rates have roughly tracked the GP.

In the winter, N was applied at an average of 0.5 g N m-2 mo-1. In February and March, as the grass came out of dormancy and the GP approached 1, the N rate has been 3 to 4 g N m-2 mo-1. The P and K are applied in proportion to the amount of N applied, in the approximate ratios used by the grass.

The mower bench setting was 4.25 mm in early April when the photo was taken, with a 3 mm prism reading on the ground.

These are new greens, planted in autumn 2015.

Even for new greens, those are still pretty impressive results. Sure, one doesn't putt on the roots -- what really matters is the surface. But these photos demonstrate that supplying the grass with the nutrients it can use, at the time when net photosynthesis is at its highest, and given water and air in the soil, roots are going to grow.

Is this the most common oxymoron in turf?

An oxymoron is a contradiction in terms, and the one about nutrients being present but not available, or exchangeable but not available, or adequate but limited, is one I hear again and again.

Paul Walsh recently posed this common question:

I've tried previously to answer this in a lot of different ways:

Let me answer in a slightly different way this time.

First, it's an oxymoron to think of availability in terms of present but not available, or adequate but of limited availability. A clearer way to think of this, and the way that I try to express it now, is enough or not enough. For any element, is there enough to meet the grass requirements, or is there not enough? The MLSN guidelines provide an answer to this question.

Second, have you noticed what is missing in all this discussion about the semantics of availability? Turf performance. That's what is missing. I want to know if there is enough, or not enough, in order to produced the desired turfgrass surface. Sure, the solubility of different elements changes with pH. Sure, the ion exchange characteristics of the soil change with pH. But only when turfgrass performance is affected do we need to worry about this. So I suggest going back to the first point: is there enough or not enough?

Here is grass performing just fine across a range of pH from 3.7 to 9.5. Yes, the soil chemistry changes across that pH range. Yes, there will be differences in nutrient solubility. But the grass is fine. You'll see that there is enough in each of these soils.

Soil pH from 3.7 to 7.4


Soil pH 6.5


Soil pH 7.8


Soil pH 8.3


Soil pH 9.5