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February 2015

Silica and Green Speed

This is something that has never made sense to me. Actually, it seems ridiculous. Zoysia greens are not renowned for being especially fast. But zoysia has especially high silica content in the leaves. Duble, writing about Zoysia: "The species vary from extremely fine textured to coarse textured types and the leaf blades are very stiff due to a high silica content."

So if silica does make greens faster, shouldn't zoysia greens be lightning fast?

I was reminded of it this week, so I checked Nikolai's fine book, The Superintendent's Guide to Controlling Putting Green Speed, on the topic. I'd heard that silica application is supposed to increase green speed by making the leaves more turgid. I looked up the topic in Nikolai. He mentioned one study by Trenholm et al. on seashore paspalum in which silica application led to "increased turgor pressure of the turfgrass leaves."

Then, Nikolai had this short statement:

"For this reason, it is assumed that silica might enhance green speed, but, unfortunately, no study has tested this notion ... Clearly, more data is needed on this subject."

The book came out ten years ago. Anyone have some data on this subject since then?

I've reviewed 540 stimpmeter readings I made in 2011. These greens were in Japan, Vietnam, USA, Philippines, India, and Thailand. The species are listed in the table below, along with the average green speed by grass species.

species # of measurements average speed (feet)
creeping bentgrass 249 8.7
bent-poa 18 9.9
bermuda 107 8.5
fine fescue 15 8.6
zoysia 42 7.8
seashore paspalum 90 8.2
Poa annua 19 9.9

This is nothing against zoysia greens. Zoysia greens can be quite good.

Above is the 18th at Wack Wack during the Philippine Open. Below is roll on a zoysia green at Keya Golf Club in Japan.

The roll can be excellent. But it takes a lot of work to get the conditions shown. Just a high silica content of the leaves, and a high turgidity of the leaves contributing to faster green speed? I don't get it.

Honda LPGA at Siam CC, Novotek, Seashore Paspalum, and the #STMIA15 Field Day

The 2015 Honda LPGA Thailand is underway at the Siam CC Old Course this week. Here's a look at the first round highlights.

The greens are Novotek bermudagrass, and the fairways are seashore paspalum. They look great. And the players are making lots of birdies and even eagles on these smooth greens.

At Siam CC, there are 3 courses on adjacent property. The Old Course, closest to Pattaya, down the valley to the Waterside Course, and up the other side of the valley to the 27 hole Plantation Course.

On March 10, the Waterside Course will host the Asian Turfgrass Field Day -- preview here. This is part of the Sustainable Turfgrass Management in Asia 2015 conference. Also, on March 12, conference delegates have the chance to play golf at either the Plantation (host venue for the 2015 Thailand Open) or the Waterside Course at a special conference delegate rate.

"Nothing mysteriously beneficial in their formulas"

Selection_051Yesterday's Turfgrass Talk Show at GIS had an interesting topic. Interesting, in that I presume by fertility what is really meant is turfgrass nutrition. And interesting, in how the word fertility is so misused.

Look up fertility in the dictionary -- it means the quality of being fertile; fruitfulness; productiveness. Fertility is. It is not something one adds or subtracts. That is fertilizer. One can't add a little more fertility, or reduce fertility -- that just doesn't make sense.

Charles Vancouver Piper, the first chairman of the USGA Green Section, wrote an article on this in 1919, entitled "The Words Productivity, or Productiveness, and Fertility as Applied to Agriculture." Here are a few passages from the article:

The word fertility ... was originally used by the Romans when applied to agriculture with the meaning of fruitfulness, that is, productiveness in large measure.

The word fertility in modern times has tended to become more and more restricted to the conception of soil fertility, thus excluding the other potent factors that make for productivity.

In view of the fact that the word fertility is often used in agriculture in the narrow sense of soil fertility, as well as in its broader original meaning, it is an unsatisfactory and often ambiguous term to use in technical publications.

As before stated, the word fertile means productive in a high degree. Therefore, it approaches the absurd to speak of low fertility, moderate fertility, etc.

Piper suggested not using the word. I mentioned this yesterday, and James Hempfling asked if Piper had discussed this topic in Turf for Golf Courses. [Note that this book is one of many with full text available from the Turfgrass Information Center.] 


Today I went to the Fertilizers chapter of the book, to see how Piper and Oakley had used the word fertility. Turf for Golf Courses was published two years before the fertility terminology article. They used the word just five times in the entire book, and only one time in the Fertilizers chapter. And in all cases, they used the word to refer to soil fertility, specifically to the nutrient supplying capacity of the soil.

But enough about that. What was really interesting was this advice about fertilizers:

It is a common practice of commercial fertilizer companies to mix fertilizing materials in different proportions with the view to selling them for special conditions. These ready-mixed fertilizers are extensively advertised under various trade names such as "Turf Grower," "Grass Grower," "Lawn Fertilizer," and the like, and the opinion seems to prevail in the minds of many that they are just what is required. While these mixed fertilizers are very generally used, they are not to be recommended. Commercial concerns possess no special information regarding the action of fertilizers on grass that an intelligent greenkeeper cannot soon acquire, and, therefore, there is nothing mysteriously beneficial in their formulas.

When mixed fertilizers are desired, it will be found cheaper and generally more satisfactory to buy the ingredients separately and combine them in suitable proportions. By doing so the purchaser does not have to pay a high price for a considerable quantity of inert filler that is commonly present in ready-mixed fertilizers.

For more about the exciting life of C.V. Piper, this profile tells how he climbed Mt. Rainier with John Muir, collected plants and grasses around the world, and what happens to one's golf game after becoming interested in golf course design, construction, and maintenance.


A humorous, numbered, and long one: "I'm not an enthusiast for diversity of opinion where factual matters are concerned"

I'm going to throw all kinds of things together here.

1. This post on Pitchcare shows that there is a diversity of opinion about turfgrass nutrition and the interpretation of soil tests.

2. I received a question about that particular post, tried to answer it here, and it ended up being quite a lengthy discussion on a range of topics (see the comments section at the bottom too).

3. My approach to turfgrass nutrition specifically, and turfgrass management generally, is that it is simple, but not easy; if we can identify the principle factors influencing turfgrass performance, and modify them, we will be making great progress toward our goal of producing the desired turfgrass surfaces. When it comes to turfgrass nutrition, I suggest making sure that soil nutrient levels are kept above the MLSN guideline levels.

We are very open about how we develop these guidelines, which data are used, what our assumptions are, and we even share the code we use to generate the guidelines. We study this topic intensively, and we only recommend or suggest nutrient application when we are confident it will have an effect on turfgrass performance. This approach reminds me of these comments by Richard Dawkins on facts vs. opinion:

I don't give a damn for anybody's opinion; I only care about the facts. So I'm not an enthusiast for diversity of opinion where factual matters are concerned.

Watch/listen to Dawkins here.

4. I spoke with Frank Rossi on TurfNet RADIO about turfgrass nutrition and nutrient guidelines. This conversation is about facts, and doesn't give a damn for opinions. If you do turfgrass maintenance, you should be aware of what we talked about.

5. I've been writing here since January of 2009, and I've never mentioned BCSR. I make an exception today, to share this point by Max Schlossberg (with counterpoint from Joel Simmons) about how soil tests are done and interpreted and how fertilizer recommendations are made.

Max has an account on Twitter now. I'm excited about that because he has great insight to share about turfgrass nutrition. And a lot of other things too, but I'm especially counting on him to correct me when I err.

6. Turf nutrition doesn't have to be that complicated. Turf maintenance in general doesn't have to be that complicated. You can think it is complicated if you want to. I take the approach that we try to modify the growing environment of the turfgrass to create the desired playing surface, and we take special care to control the growth rate of the grass. If we do those things, which in principle are simple, but which in practice may require a lot of work, we achieve the desired turfgrass conditions.

I am not going to rewrite all on these topics here. If you are interested, read more of the other posts on this blog. But please do contrast the simplicity of the approach I describe, and the MLSN approach, to the more complicated description here:

And it continues here:

Actually, those complicated descriptions of nonsense weren't about turfgrass fertilizer. But you may have heard or read descriptions of turfgrass products and maintenance that were approaching that level of complexity. It really shouldn't be like that.

7. Everyone probably knows about Occam's razor. I had a great discussion about this with John Bladon last month. If you don't know what this is, you can read about it here.

Frankly Speaking about turfgrass nutrition, the MLSN guidelines, & the GSS on TurfNet RADIO

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

I had a chance to talk with Frank Rossi tonight on TurfNet RADIO. We discussed turfgrass nutrition, soil testing, the MLSN guidelines, the Global Soil Survey (GSS), and not much else. But Dr. Rossi has a way of asking interesting questions, and I tried my best to answer them in a way that makes sense. Have a listen to our discussion and see if we succeeded!

For more information about the things we discussed, here are direct links:

"Do you have a rough guide of all MLAN ranges for nutrients?"

This page in Carrow et al.'s Clarifying Soil Testing series has a list of SLAN guidelines.

I received that question by e-mail. It's a good one to answer in that I can point out the differences between the SLAN (sufficiency level of available nutrients) and MLSN (minimum levels for sustainable nutrition) guidelines.

1. The SLAN guidelines are in this article.

2. The MLSN guidelines are in this file.

3. This article in GCM points out why the MLSN guidelines were developed and how to use them. We wrote:

Conventional guidelines [the SLAN guidelines] are not only complex, they are also relatively static, without regular or systematic updates. However, regular updates seem like a good idea, because many research projects suggest that high-quality turf can be produced at levels below the conventional guidelines.

4. I can't stress enough how much I prefer the MLSN approach to SLAN. First, SLAN guidelines are not updated and no one is supporting them. MLSN are under continuous review and development. Second, MLSN allows one to calculate a fertilizer requirement for any grass grown anywhere in the world. Please read about SLAN for turfgrass, try to calculate a fertilizer requirement, and then tell me how it is done. I can't figure it out. And I bet you can't either. The SLAN guidelines are nice to look at in a table, but they are ambiguous in the amount of fertilizer that will be recommended.

A hypothesis concerning the most important time for sunlight to fall on turfgrass

Adam Garr asked if there is a great resource on morning light for turf:

I have a hypothesis about this. I wrote it on Twitter in response to Adam's question, but I got it slightly wrong, in that I wrote max DLI when I meant max PPFD -- or something like that. Here's my hypothesis.

The most important time for full sunlight to reach a turfgrass surface corresponds to the optimum temperatures for photosynthesis for that species. More specifically, the longer the duration of time at which the PPFD on the turf surface is near the maximum the grass can use, while at the same time the air temperature is close to an optimum for photosynthesis, will optimize turf performance.

Turf grows best in full sun. But full sun is a concept -- the reality is there are clouds, trees, buildings, mountains, and whatever other causes of shade that exist. My hypothesis would predict that morning sun, when temperatures are cool, would be better for cool-season grass in the heat of the summer, when afternoon temperatures are better for photorespiration than for photosynthesis. My hypothesis also predicts that morning sun is less important for warm-season grass in hot weather, because it is the afternoon sun combined with high temperatures that produces the maximum carbohydrates for those species.

I've got lots more to write and say about this. For a couple of things you can look at now, if you are interested in this topic:

1. It is, I hope, more general than the title suggests. How much do clouds affect photosynthetic irradiance? Measures of light at Thailand, Hong Kong, Vietnam, and Japan.

2. Presentation slides from a talk about Eternal Sunshine of the Spotless Green at the NTA conference.

"Perhaps I am reading too much into it"

Selection_043More about that Bah! Humbug! thing.

In reference to this discussion on Pitchcare, Mario Ernst sent me this question:

Pretty much at the same time you added the post "Concerning the Availability of Nutrients" I have come across a discussion in a forum about this topic.
There is a passage that has confused me a bit:
"Grass with a good population of mycorhhizae in the root system may need 50% less fertiliser than non mycorrhizal grass. Unfortunately high iron concentrations sometimes reduce beneficial fungal levels but generally mycorrhizal colonisation rate is one of the most important factors in determining the amount of fertiliser required to maintain healthy plants.
The analysis (soil test) only measures the available extractable/exchangeable levels of nutrient. It does not measure the total levels. Locked up nutrients become available due to solubilisation by organic acids and by microbial activity, mycorrhizae produce enzymes which make a lot of nutrients available, especially phosphate and many bacteria and fungi also solubilise locked up nutrients."
The person that wrote this seems to argue that soil test (extractant not known here) results in general do not give a clear picture since they don't consider the influence/activities of acids and organisms between consecutive soil tests. The logic behind it also seems to be that there may be a higher amount of nutrients in solution during the summer as opposed to early spring when many people send out their soil samples...or perhaps I am reading too much into it. In one of your posts you wrote
Not all nutrients in the soil are available for plant uptake. But they don't have to be. We just need to know if there are enough, or not enough...
...nutrients available in solution and on the exchange sites, that is, correct?

Could you help me clarify whether the points (mycorrhizae in particular...e.g. should the impact of the fungi be taken into account somehow for example by calculating with an adjusted rootzone depth) above do affect how one should look at soil test results or is the answer once again Bah! Humbug!...?

My response in short -- this is making it more complicated than it needs to be. Here's what I wrote immediately, before I had seen the entire thread on Pitchcare:

The person that wrote that is making the common error of not understanding how one uses and interprets a soil test.

Because the soil test level is calibrated to turfgrass response, we can say that turf growing in soil with 8 ppm P by the Mehlich 3 test is very likely to respond to P application, while turf growing in soil with 50 ppm P by the Mehlich 3 test is almost certainly supplied with enough P.

The soil test data are not just random numbers unrelated to turf performance. The soil test guidelines, if they have been developed in a standard way, are related to probable turf response. So the soil test value is compared to the guideline and one can then make a decision about application of that nutrient.

That means that ALL of the information about the availability of a nutrient, in terms of is there enough of it available or not, is embedded in the soil test result.

If one interprets soil tests in another way, what is the point of testing?

After I found the thread and read it, I have a few more thoughts.

First, I wouldn't be so harsh in my wording about "the person that wrote that." After I read the thread, I thought it was a reasonable post, with a reasonable interpretation of the soil test, and a reasonable recommendation of how to fertilize the rugby pitches in question. Although I would add a little manganese in this case too.

Second, the mycorrhizae are not really related to interpreting soil tests. We can expect mycorrhizae in turf soils, and if there are more mycorrizae, the effective root system will be larger, so the quantity of an element such as P required on the soil test would be lower in a soil with more mycorrhizae than in a soil with fewer. But this makes it unnecessarily complicated. P in the soil will change through the season. The root system size and architecture also changes through the season. The plant demand for P changes through the season. The amount of mycorrhizal infection of the roots changes through the season too. All these things are in flux. And largely irrelevant.

What is relevant is that the value of an element (P in the example I am using) is enough or is not enough to produce good turf. It is not about locked up, exchangeable, or seasonal variables, or mycorrhizal counts, or anything like that. One just gets the soil test number, compares it to a guideline, and decides if the soil levels of P can meet the plant requirement, or if fertilizer P is required.

If one cannot trust the guideline, or believe the number, then the soil test was a waste of time and money. Soil testing is useful as a decision-making tool to determine if an element should be applied as fertilizer. If one does a test, and then cannot make a decision, what was the point?

I like to use the MLSN guidelines because they are developed from more than 3,000 soil samples, with turf of multiple species, sampled throughout the year, and in all the turf was performing well. That means that at the time the sample was taken, that amount of an element, as measured by the Mehlich 3 extractant, was sufficient to produce good turf. And we can then make calculations of how much the grass may use going forward, to make sure that the fertilizer recommendations keep that element from dropping below the MLSN guideline.

Concerning the availability of nutrients in soil

The most common question I receive is some variation of this: "What about nutrients in the soil that are not available?"

That question throws me for a bit of a loop, because the very purpose of soil testing is to find the availability of nutrients. Let me try to answer this question three times, in progressive order of complexity.

1. "What about nutrients in the soil that are not available?"

Answer: Soil tests already take availability into account. So one doesn't need to consider the term "availability." Just look at the number on the soil test and compare it to the guideline value that you choose. I think the most accurate values to compare to are the MLSN guidelines.

2. "What about nutrients in the soil that are not available?"

Answer: Marschner's Mineral Nutrition of Higher Plants has a chapter conveniently entitled Nutrient Availability in Soils. It begins:

The most direct way of determining nutrient availability in soils is to measure the growth response of plants by means of field plot fertilizer trials. This is a time-consuming procedure, however, and the results are not easily extrapolated from one location to another. In contrast, chemical soil analysis -- soil testing -- is a comparatively rapid and inexpensive procedure for obtaining information on nutrient availability in soils as a basis for recommending fertilizer applications.

Soil testing already provides information on availability.

3. "What about nutrients in the soil that are not available?"

Answer: Bah! Humbug!

See these links for more detail:

Is sodium an imaginary problem?

On sand putting greens, it is. The problem caused by sodium is a reduction in the downward movement of water in soils. This is caused by the deflocculation of clay in the soil. It is a real problem in soils with appreciable amounts of clay, and in those soils, an exchangeable sodium percentage (ESP) of 15% or more is indicative of potential problems. The solution? Add gypsum to reduce the ESP, and add water to leach the sodium.

But in sand rootzones, what happens when there is a high ESP? Obear and Soldat wrote about this in their recent Soil Science paper, Saturated Hydraulic Conductivity of Sand-based Golf Putting Green Root Zones Affected by Sodium.

Selection_041In this experiment, they constructed 6 sand rootzones, with 5 with amendments, and 1 without. The sand was mixed with each amendment in a 4:1 ratio by volume -- 4 parts sand, 1 part amendment.

  1. Nonamended sand
  2. Sand + peat humus
  3. Sand + Profile
  4. Sand + sphagnum peat
  5. Sand + silt loam
  6. Sand + loam

Then, "the soil cores were placed in plastic tubs and allowed to equilibrate for 48 h in a range of solutions of differing ratios of sodium chloride, calcium chloride, magnesium chloride, and potassium chloride." These solutions ranged in sodium adsorption ratio (SAR) from 0 to infinity, including two solutions with high sodium (37 mmol/L and 185 mmol/L, respectively) and no calcium, magnesium, or potassium.

After these equilibrations in solutions of different SAR, each of the soils had some cores with ESP < 15%, and some with ESP > 15%. How did the sodium influence the saturated hydraulic conductivity (Ksat) of the soils? It didn't do much, except for the sand mixed with loam, which had a clay content by weight of 4.8%. In the unamended sand, sand mixed with peat, or Profile, or silt loam, increasing ESP did not reduce Ksat. In fact, in the unamended sand, the Ksat actually increased after the soil was equilibrated with high SAR solutions.

These are some key results:

In the case of sand-based golf course putting green root zones, which often have very low clay contents, increasing ESP well above the standard sodicity threshold of 15 had no effect on Ksat.

The application of soil amendments for remediation of sodic soils (e.g., gypsum) would only be warranted for sodic soils with higher clay contents and may not provide significant infiltration benefits to sand-based golf course putting greens.

This study also provides evidence that increasing exchangeable Mg2+ [magnesium] does not affect Ksat of sand root zones.

For more about imaginary problems in turf maintenance, see: