Two completely disparate things

These things aren't related, except as a follow-up to podcasts I listened to. The topics on my mind: synthetic nitrogen and soil carbon, and disagreeing with some stuff.

I recently enjoyed listening to these TurfNet Radio podcasts. I think you will too.

Dave Wilber, in his monologue, mentioned that he "disagrees with some stuff" that I've been working on. I'm interested to have that conversation with him. Can you guess what it is that we may disagree about? I can, but I don't think the details will come out until we talk.

I'd usually say, the wonderful thing about blogs, and comments, is that one can respond and disagree and make corrections and arguments almost in real time, without waiting, and I was going to ask Dave to please do that. But I think he must have a good reason for waiting to give the details of his disagreement, plus it leads to more anticipation for that forthcoming podcast!

And it reminds me of something I disagree with, and that I was disappointed to see, and that I will go ahead and share. It ties in with the "clear as mud" comment from Mark Hunt after seminars at GIS this year. I'm disappointed when I hear those kind of comments, especially when the topic is turf nutrition, because I don't think turf nutrition needs to be complicated, and I think it is unfortunate that seminars can leave someone with that impression.

I didn't go to GIS this year, but I was glad to see so many of the presentations made available for download on the GCSAA website. I wish more presentations were shared. By the way, most of my presentation slides from the past few years are available at SlideShare, SpeakerDeck, or through the /seminar tag on the blog. When those GIS presentations were available, I downloaded and read the ones I was interested in, most especially The Knowns and Unknowns of Nutrient Uptake by Roch Gaussoin. There is a lot of valuable information in that presentation, and lots of things I agree with, but one statement on slide 44 can't possibly be right.

The statement I refer to is this: even if there is an optimum level of nutrients in the root zone, it may not be readily available. If that statement were true, then by definition there is not an optimum level of nutrients.

So that's something I disagree with. I look forward to a discussion with Dave Wilber in due time to see which of the things I've been working on are ones he disagrees with. By clearing up all the disagreements, we should move closer to the right understanding.

The second topic was discussed when Frank Rossi spoke with Bruce Branham. It relates to the N source, and the question is, when inorganic N is added to turfgrass, does that cause an increase or a decrease in soil organic matter/soil carbon? I also had a question about this from Ben Polimer:

 You can listen to Rossi and Branham discuss this topic in a lot more detail. I have three thoughts on the matter.

1. The research in question is on field crops, not grassland. Turfgrass systems are different. Soil carbon probably doesn't increase forever under turfgrass, but after establishing turf, the soil carbon is expected to increase for some years.

2. It seems that inorganic N applied to turfgrass causes an increase in soil organic matter. If inorganic N addition reduced organic matter, one could solve thatch problems and eliminate the need for coring and reduce the sand topdressing requirement by adding inorganic N fertilizer.


3. Data from Table 3 in Hopkins et al. (2008) are plotted above. The plot shows soil organic carbon from selected subplots of the Park Grass experiment receiving different fertilizer treatments, with the soil organic carbon measured in 1876, 1959, and 2002. Park Grass is not turfgrass, but it is permanent grassland, cut for hay twice per year. In a comparison of soil organic carbon from samples collected in 1872, 1959, and 2002, one can see that the addition of inorganic N fertilizer -- ammonium sulfate -- to plots 18d and 1d has led to increased soil organic carbon compared to those plots that have not received inorganic nitrogen.

Mineral nutrients in the leaves vs. those in the soil

Last year I shared an elemental cartogram of relative mineral nutrient amounts in turfgrass leaves. An elemental cartogram is a periodic table of the elements with the area of each element modified by a theme, and in this chart the area is modified by the amount of mineral nutrients.


One thing I notice on the cartogram of mineral nutrients in bentgrass leaves is this: where are the micronutrients? We can see the macronutrients clearly: N, K, and P. Then the secondary nutrients: Ca, Mg, and S. But the micronutrients are in the leaves in such small concentrations that they don't register on this cartogram, in which their quantity is compared to those of the macronutrients and secondary nutrients.

The quantity of an element required as fertilizer is the difference between the amount the grass requires and the amount present. I wondered how the cartogram of elements in leaves would compare to a cartogram of nutrients in the soil. For that, I looked up the Global Soil Survey data, and generated a cartogram using the median values of the elements measured in the Global Soil Survey.

Selection_044This looks a bit different, and is illustrative of a couple things related to fertilizer. First, N is low in the soil, but the plant uses a lot of N. Comparing the two charts makes it clear why N is applied as fertilizer to most turfgrass sites. Second, K is relatively large in the cartogram for leaves, and much smaller in the cartogram for soil. Because the plant demand for K is relatively high, compared to the amount in the soil, K is often required as fertilizer. Third, Ca and Mg and some micronutrients are much higher in the soil than they are in the leaves, providing an illustration of why these elements are rarely required as fertilizer.

Waterfall charts provide a more explicit example of these calculations, but the cartograms are kind of fun to look at.

The 2015 Global Soil Survey report and data are now available

Selection_040The end of August marked 2 years of the Global Soil Survey. This report gives a summary of the results so far, shows a map of the locations -- now up to 9 countries! -- from which samples have been submitted, and announces that the survey will end on 31 December.

Thanks to all who have participated in this project for contributing samples from good performing turf at their sites. We now have a dataset which can be used for comparative analyses and as a reference for soil chemical conditions of professionally managed turfgrass.

A few related links:

This pretty much covers everything

Selection_039In January at the Northern Green Expo, I get to talk about light, water, temperature, and nitrogen. Those are the factors that influence growth, and getting the growth rate right is what greenkeeping is all about.

There are five different seminars, all linked by that common theme.

The (New) Fundamentals of Turfgrass Nutrition

Most seminars, presentations, articles, and even semester-long courses about turfgrass nutrition discuss the functions of different elements. Potassium is involved in stomatal regulation, phosphorus is essential for root development, calcium for cell wall strength, and so on. All true, but largely irrelevant for the turfgrass manager. What the turfgrass manager must know is not the function of each element, but the quantities -- is enough of this element present to meet the grass requirements, or is it not? If it isn't present in adequate quantities, how much must be added to ensure the grass has enough? In this seminar, the fundamentals of turfgrass nutrition will be explained, with a focus on an understanding of the amount of each nutrient that is required.

Nutrient Use by the Grass and Nutrient Supply by the Soil

Grass grows in soil, and nutrients used by the grass come either from the soil or from fertilizer. When the soil contains enough of an element to meet all of the grass requirements, none of that element is required as fertilizer. When the grass can use more of an element than can be supplied by the soil, that element must be applied as fertilizer. This seminar will explain how to estimate the maximum amount of an element the grass can use, how to identify the quantity that can be supplied by the soil, and how to use those two amounts to get an estimate of the amount that may be required as fertilizer.

Calculating the Fertilizer Requirement for Any Turfgrass, Anywhere

This presentation builds on the fundamentals of the turfgrass nutrition talk, and the nutrient use and nutrient supply talk, by explaining a system by which a turfgrass manager can calculate the amount of any element required by any turfgrass, under any growing condition, anywhere in the world. Some common misapprehensions about turfgrass nutrition and soil testing will also be discussed. The minimum levels for sustainable nutrition (MLSN) guidelines for interpreting soil test results, and the temperature-based turfgrass growth potential (GP), which were introduced in the two previous seminars, will be discussed in even more detail.

Soil Water Management: Timing, Amount and Syringing

Fifteen years ago, it was rare to use a soil moisture meter. Today, it seems that almost every turfgrass manager has some idea of the soil moisture content. In this presentation, Micah Woods will show that daily irrigation can use less water than infrequent irrigation, while maintaining a lower soil moisture content than deep and infrequent irrigation. Woods will explain how soil moisture meters can be used to prove that, how they can be used to measure the real evapotranspiration rate, and why syringing turf for the purpose of cooling the surface is a waste of time, water, and energy.

Instead of Shade, Let's Talk About Light

Shade from trees, buildings, clouds or mountains affects a lot of turfgrass areas, and shade can make it impossible to produce the desired turfgrass conditions. Rather than talk about the impossible, in this presentation Woods will talk about light. Specifically, he'll discuss photosynthetically active radiation (PAR), the photosynthetic photon flux density (PPFD), and the daily light integral (DLI). These sound complicated but are quite simple and can be easily measured or estimated. With an understanding and ability to measure and communicate about PAR, PPFD, and DLI, it makes it a lot easier to manage those previously impossible shade problems.


Monthly Turfgrass Roundup: October 2015

Here's a roundup of turfgrass articles and links from the past month:

Bill Kreuser shared a video about pigments/colorants.

You can read the abstracts of the newest turf research projects.

Not what one wants to hear after an educational conference: "as clear as mud".

Rain and fungus, a report from NCSU.

Light or temperature?

Benjamin Warren wrote about golf's urban future.

Bentgrass in hot places.

Frank Rossi spoke with Doug Soldat and Bill Kreuser on TurfNet Radio: listen when you have time.

I spoke at the Japan Turf Show. Here are my presentations.

Edwin Roald's conversation on Bogey Nights is a good listen, about golf for the modern era and lots more.

Is it necessary or advisable to apply potassium after a heavy rain? Four related posts on this.

1: I'd be applying potassium all the time, part 1.

2: part 2.

3: part 3.

4: How soil K changes over time.

This chart shows the average PPFD for every hour of the year so far, along with the DLI.

Details of the 2016 Sustainable Turfgrass Management in Asia conference announced, with registration available in January.



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.

How soil K changes over time

These data show what happens to potassium (K) in the soil when different rates of K fertilizer are applied. Over two years, I made 25 applications of K to a plot of L-93 creeping bentgrass in Ithaca, New York. In 2002, I made 13 applications, and in 2003, I made 12 applications. K was applied at 6 different rates, and N was supplied in equal amounts to each plot.

This chart shows the starting soil test K, before any of the 25 treatments had been applied, and also the final soil test, two years after the first one, and after all those 25 fertilizer applications had been made. I'm showing data here from the 0.01 M SrCl2 soil test (that is "hundredth molar strontium chloride") because that test has high accuracy and sensitivity in sand rootzones. These data are proportional to Mehlich 3 data, but lower in this sand by about 50 ppm. So 30 ppm by 0.01 M SrCl2 would be about 80 ppm by Mehlich 3.


Before any of the treatments were applied, the soil test K was about 29 ppm. When no K was applied, the soil test K went down. When more K than N was applied, the soil test K went up.

This next chart shows those same data, with the 25 application dates when K was applied marked in green.

K2I'd like to point out that on the final date of sampling shown here -- 30 May 2004 -- it was 7 months after the final K fertilizer application of 2003. And you'll notice that there is a big difference in soil test K, with less than 20 ppm in the plots to which no K fertilizer was applied, and more than 50 ppm in the plots to which 4.6 grams of K were applied for every gram of N applied.

What about precipitation? Shouldn't heavy precipitation cause the K to leach? That's not the way it works. From the first soil test date of 4 June 2002, when the soil test K was 29 ppm, to the last date, there were 20 days during which the precipitation was greater than 25 mm. This chart adds on those dates, marked as blue asterisks. The asterisks are jittered up and down, to avoid overplotting.

K3Each of those 20 days had more than 25 mm of precipitation, for a grand total of 719 mm (28.3 inches) just on those 20 heavy precipitation days. There were 4 such days between the last K application and the soil testing on 30 May 2004. But the amount of K in the soil looks like it was controlled by the quantity of K fertilizer applied, not by the amount of precipitation.

I wrote about this in "I'd be applying potassium all the time" parts 1, 2, and 3. Adding K based on rainfall is a sure way to apply way more potassium than the grass can use or the soil can hold. For that matter, so is adding more K than N.

What is even more important than all the soil test numbers is the performance of the grass. And all the K added in this experiment, all 25 applications of K at different rates over 2 years, didn't cause any improvement in turf performance. Here, in the flagged rectangle, are those L-93 plots to which the K treatments were applied. This photo was taken on 19 August 2003.

K trial north

At the soil test levels of K in this experiment, there was enough K to meet all the grass requirements, across the range of adding no K for every 1 gram of N (a 1:0 ratio of N:K) all the way to the highest rate of 4.6 grams of K for every 1 gram of N (a 1:4.6 ratio of N:K). All the more reason not to worry about replenishing soil K after a rain.

What one should do is look at the soil test K, make sure it will stay above the MLSN guideline for K, and then don't worry about K.

A chart of PPFD at two locations this year from January 1 through last Friday

The photosynthetically active radiation (PAR) changes through the day and through the year. The PAR is measured instantaneously for a duration of 1 second as the photosynthetic photon flux density (PPFD), and by adding up the PPFD for all the seconds in the day, one gets the daily total of PAR, which is called the daily light integral (DLI).

These charts show the average PPFD on an hour by hour basis. With a look at a chart like this, one can see:

  • how length of the day affects PAR, by looking at what time in the morning and what time in the evening the PPFD goes to 0.
  • how time of the day affects PAR, by looking at the change in PPFD hour by hour through the day.
  • how day of the year, and consequently sun angle, affects the PAR, by looking at the maximum values of PPFD at midday and seeing how they change through the year.
  • how clouds reduce the PAR, by comparing PPFD on sunny hours or days to PPFD on hours or days that don't have full sun. For more about sun and clouds and time of year, see these descriptive slides with data from 4 days in Tokyo this year: a sunny summer day, a very cloudy summer day, a sunny autumn day, and a partly sunny autumn day.

This chart shows, for every hour of this year through last Friday, the average PPFD for that hour at Tokyo (red) and at Watkinsville (blue). Each panel of the chart is a single day, and the DLI in units of mol m-2 d-1 is written on each panel, in red for Tokyo and in blue for Watkinsville.

image from

There have been 296 days this year, through October 23. On one of these days, February 10, there were erroneous data at Watkinsville, so I don't have a DLI. That leaves 295 days with a DLI for both Tokyo and Watkinsville. These locations have similar temperatures, and similar latitudes. How do they compare for photosynthetically active radiation? There have been 115 days with a higher DLI at Tokyo than at Watkinsville, and 180 days with a higher DLI at Watkinsville than at Tokyo.

I've made a couple other similar charts. This one shows the average PPFD at Tokyo hour by hour this year through October 12. Because the chart shows data for only one location, I've used color to indicate the month.

image from

And the next one is the same location and dates as the above, with the addition of the DLI written on each panel.

image from

The Watkinsville data are from the US Climate Reference Network and the Tokyo data are from the Japan Meteorological Agency.

You'll want to listen to these when you have time

I really enjoyed these two podcasts by Frank Rossi on Turfnet Radio, with guests Doug Soldat and then Bill Kreuser.

Check Out Golf Podcasts at Blog Talk Radio with TurfNet RADIO on BlogTalkRadio

They talk a lot about turfgrass fertilizer, which is something that I'm quite interested in, and I learned a lot by listening to these two podcasts. I think you will too.

Check Out Golf Podcasts at Blog Talk Radio with TurfNet RADIO on BlogTalkRadio

Why light is more important for ultradwarf than for bent: my presentations at the Japan Turf Show

I'm giving two presentations at the Japan Turf Show in Tokyo this week. In the first one, I explain why light, by which I mean photosynthetically active radiation (PAR), is more important for ultradwarf bermudagrass than it is for creeping bentgrass. I use data from Tokyo and from Watkinsville, Georgia, to demonstrate this and to point out the difference in PAR between Japan and the region of the USA with similar temperatures.

The slides for this presentation about light are available in English and in Japanese.

In a second presentation, I talk about management of ultradwarf bermudagrass greens, explaining how this species performs compared to creeping bentgrass in Japan, and how it should be managed.

The slides for this presentation about ultradwarf management are available in English and in Japanese.

Bentgrass in hot and not so hot places

Creeping bentgrass is a cool-season grass. When temperatures are hot, it doesn't perform well. I was asked if bentgrass in southern China was comparable to bentgrass in Spain. I don't think that is the right comparison. It would be more appropriate to compare southern China to Florida.

I downloaded the 2014 daily temperatures for the international airports at the cities shown in this chart, then plotted the cumulative sum of the mean temperature for the year.

SumTemperatureGuangzhou and Orlando had the same cumulative sum of temperature. Bentgrass wouldn't be a good choice in Orlando, and I don't think it is a good choice in Guangzhou either.

A better way to look at bentgrass suitability is to look at the low temperatures. If the low temperatures are too high, for too many days, bentgrass will be really difficult to manage, eventually becoming too much of a problem and one would be better off with a warm-season grass.

For 2014, here's the number of days with a low temperature greater than or equal to 22°C. I'd look at anything more than 60 days in a year above that level as being difficult for bent.

BarChartLowsThis way of evaluating the temperature fits pretty well how one expects bentgrass to perform in these locations. Perfect in Kunming, the "Spring City." Pretty good in Spain. A challenge in Shanghai summers, with some warm-season greens there also, but possible with good management. Not used in Orlando. And I wouldn't want to try it in Guangzhou.

For more about temperatures and bentgrass, see: