Viridescent - the Asian Turfgrass Center blog

Understanding Data Use for Turf Management: presentation slides (with video) from Thailand

This week I spoke to a full room of turfgrass managers at Bangkok's Thana City Golf and Sport Club about an important topic: understanding data for use in turfgrass management. I've recorded this video of the presentation slides in which I discuss the two classes of data that can be collected – data about playing surface performance, or data about plant growth – and then I go into some detail about soil moisture and photosynthetically active radiation (PAR), with a brief mention of salinity and soil pH at the end.

There were many questions and an active discussion in this seminar and in fact lunch time arrived before I could speak about salinity and soil pH, so this video provides the narration of what I would have talked about had there been more time.

David Lau from Spectrum Technologies, pictured with me at right, gave an interesting presentation in which he talked about a broad range of meters and software that can be used to collect and analyze information for improving turfgrass performance. This is part of what PACE Turf call Precision Turfgrass Management (PTM), which is a systematic effort to provide optimum turf performance using minimum resources. As David mentioned, we cannot manage something if we do not measure it.

For more information about the data I discussed, you may be interested to read this report about putting green performance, including extensive sections and data on soil moisture and temperature, and this report about photosynthetic irradiance.

The Unambiguity of Nutrient Availability Indices

I've been asked a question about nutrient elements being "locked up" in the soil and if I could explain that. This question is in some way related to these posts about soil testing and nutrient requirements:

• How much potassium does grass require?
• How much phosphorus does grass require?
• How much calcium does turfgrass require?
• Calcium deficiency in turfgrass, an imaginary problem?
• Turfgrass nutrient requirements and fertilizer choice
• Sand, sodium, and soil structure
• A fertilizer miscellany: cost, phosphite, and nutritionism
• PACE Turf and the minimum levels for sustainable nutrition (MLSN) guidelines

In those posts, I have not used the terms "locked up" or "tied up" to refer to nutrients in the soil that are unavailable for plant uptake. Those terms should not be used by professional turfgrass managers because they are ambiguous and do not give the mechanism by which the nutrients are supposedly unavailable.

If we would say that some of the phosphorus (P) applied as fertilizer becomes "locked up" in the soil, what does that really mean? Does it mean the P will be forever unavailable for plant uptake? Does it mean the P is temporarily unavailable? Does it mean that all the soil P is at risk of being unavailable? Should we use a liquid fertilizer instead, to avoid this ambiguous "lock up" in the soil? And what about calcium (Ca) in a high pH soil, is it "locked up" in the form of calcium carbonate? The questions go on and on, but cannot be answered clearly because of vague terminology. It is often the case that this ambiguous terminology goes together with dubious chemical assumptions.

We avoid these problems by using nutrient availability indices, of which the MLSN guidelines are an example. A nutrient availability index does not try to say that a certain pool of measured nutrient are all of that element available. It is simply a number that, if it has been carefully calibrated with turfgrass response or turfgrass performance, can be used to determine the probability of a plant response to additional applications of that nutrient. 

In the soil, there are various forms (pools) of the nutrient elements. With potassium (K) for example, there will be some in soil solution, some on cation exchange sites, some in what is termed non-exchangeable forms, some in the soil particles (structural K), and some, perhaps, in undissolved or unreleased fertilizer granules, and a small amount in soil organic matter. But an availability index for K does not need or attempt to assess all of this. In the case of the Mehlich 3 extraction for K, we would be extracting from the soil almost all of the soluble and exchangeable K and a small portion of the non-exchangeable K and none of the structural K. But that index is useful, because after many experiments and calibration and study, we are confident that a value of 35 ppm K is sufficient for excellent turfgrass performance. 

If the index is less than 35 ppm, we would expect a positive response to added K. If the index is above 35 ppm, we do not expect a response to added K. Availability indices such as the MLSN guidelines are unambiguous and already incorporate the "locked up" nutrients. 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. The MLSN guidelines provide an unambiguous answer.

How Much Potassium Does Grass Require?

In last week's TurfChat, in which we discussed the relationship between soil nutrient levels and weeds, I mentioned that recommendations for soil potassium (K) tend to be unreasonably high. We can see that particular section of the discussion beginning at the 31:55 time of the TurfChat video:

The most accurate, and consequently, the most useful, guidelines for interpreting soil nutrient levels for turfgrass are the minimum level for sustainable nutrition (MLSN) guidelines. These guidelines have been specifically developed for turfgrass with special consideration of the sandy soils that are commonly used for high traffic turfgrass areas.

The MLSN guideline for K is 35 ppm.

I mentioned in the video that conventional guidelines are much higher, ranging typically from the conventional PACE Turf guideline of 110 ppm to the Penn State University target of at least 180 ppm. But there is no reason for soil K to be so high, nor can we expect most turfgrass soils to hold that much K.

When we look at the results of relevant research papers, we see that the recommendations developed after the completion of carefully controlled experiments give guideline levels very close to the MLSN guideline. Here are just a selection of typical results.

Ebdon et al., 2013: less than 50 ppm, Morgan extraction, "there were no observed changes in shoot and root growth in response to K fertilization even at low soil test K levels"

Paul, 1981: 20 ppm, ammonium acetate extraction, "beyond 20 ppm, there is no response to K fertilization"

Sartain, 2002, 30 ppm, Mehlich 1 extraction, "the critical Mehlich-1 extractable level of soil K appeared to be near 30 ppm"

Woods et al., 2006, less than 50 ppm, Mehlich 3, Morgan, and ammonium acetate extractions, "the current target ranges of extractable K in sand rootzones promote K fertilizer application that may be detrimental to turfgrass performance. Recommended levels of soil K should be reevaluated to avoid gratuitous use of K fertilizers"

The MLSN guidelines have done just that, and the methodology used to develop the MLSN guidelines results in a recommendation in line with those developed through controlled field research.

There are a number of implications resulting from using outdated and inaccurate K guidelines. It is obviously a waste of money to apply unnecessary potassium. There is wasted thought in trying to solve an imaginary problem. Application of K will reduce, unnaturally, and possibly to the detriment of plant health, the amount of calcium and magnesium in the grass. In some situations, it is expected that addition of K will increase the number of weed species that can grow. And unnecessary applications of K may cause other unexpected problems, such as increased disease.

10 Years Ago Today, a Startling Observation About Potassium and Snow Mold

Ten years ago today, I was a graduate student at Cornell University, and after the snow had melted off of the research green, I walked over to the research area to check the condition of my experiment. It was a cold day, in early spring, and I took this picture not noticing so much about the differences in snow mold incidence on the L-93 creeping bentgrass of this experiment. It was not until April (see below) that I really noticed what a huge difference there was between the different fertilizer treatments.

In the previous summer, the turf was all the same, showing no visual response to any application (or withholding) of potassium (K) fertilizer.

And in the autumn of 2002, just before the snow would fall and would cover the green for months, there was no difference at all in turf performance.

The previous summer the turf was all the same, no matter how much K was applied, and in November before the snow the turf was all the same also. There was more K in the leaves where K had been applied, and there was more K in the soil, where K had been applied, but the visual appearance of the turf was all the same. 

I did not apply any fungicides to this experimental area in the autumn of 2002. 

In the spring of 2003, when the snow melted, I expected that all the plots would be the same, as they were in November before the snow fell.

So it was a startling observation to find that there was more snow mold damage on the plots to which K had been applied in the previous year. The plots with more available K in the soil, and the plots with more K in the leaves, had more damage from snow mold than did the plots to which no K was applied at all the previous year!

I wrote about this in my article summarizing this experiment. Continuing research by Moody and Rossi has shed more light on just what it is that may cause this phenomenon. 

Application of K when it is not required may cause unexpected problems. By using the MLSN guidelines to determine when K fertilizer is required, one can have confidence that unnecessary fertilizer applications are being avoided.

Manilagrass Tees and Divot Problems, Fact or Fallacy?

Yesterday I shared this photo from Takarazuka Golf Club near Osaka. I mentioned that the manilagrass (Zoysia matrella) tee, even though it is on a par 3 hole, and even though the course has been open and busy for the past five months, five months in which the grass has been dormant, we see that the condition of the turf is still quite suitable for golf. And that is after five consecutive months of no growth.

I pointed this out because I know manilagrass can provide a superb playing surface in tropical Southeast Asia, even on tees, but I have often heard objections to the use of manilagrass, especially on tees, because of its supposed slow recovery from divots. I believe that is a fallacy, certainly in tropical Southeast Asia, and I think the situation with manilagrass and tees in Japan can inform us of a great deal on this particular subject. 

After more than four months of dormancy, a tee at Hirono GC near Osaka

Japan has about 2,400 golf courses, of which the tees are overwhelmingly manilagrass, which is called korai (コウライ) in Japan. In a recent survey of grass types on golf courses in Japan, more than 75% had manilagrass tees. So we are looking at about 1,800 golf courses in Japan with manilagrass tees. And the climate is such that the manilagrass will go dormant sometime in November and will start to grow again in April. The dormant period for manilagrass in most parts of Japan will be five to six months.

Golf is a year-round and all-weather sport in Japan. I've written about the ordeals of greenkeepers in removing snow so courses can open, and courses will be open all through the year except in the northern and mountainous regions that have extended snow cover.

The courses are played extensively while the manilagrass is dormant, but the grass survives, the playing surfaces are acceptable, and the divots, which occur month after month through the winter with no recovery at all, do not become a major problem.

A manilagrass tee on a par 3 at Keya GC in late March, photo courtesy of Andrew McDaniel

In fact, there is plenty of turf remaining on the tees, even at the end of winter, and once the weather warms up, and the manilagrass starts to grow, the tees have a full cover of grass with minimal divots. And during the growing season for manilagrass in Japan, there is little concern about divots on manilagrass tees at all. It's just not a major problem. The tees get beat up a bit in the winter, but they don't fail, and they are fine for the rest of the year.

If manilagrass works on over a thousand courses in Japan, and only grows for part of the year, and still produces a fine surface for tees, shouldn't we expect it to work well in a tropical environment, where the temperatures are nearly at an optimum for manilagrass growth 365 days a year?

A fine-bladed manilagrass tee on a busy par 3 hole at Muang Kaew GC in Bangkok; about 72,000 rounds a year are played at this course

When we do look at manilagrass tees in Southeast Asia, we find that the turf is generally just fine. In fact, I would argue that the average manilagrass tee performs better than the average Cynodon tee. And manilagrass can outperform seashore paspalum too.

Seashore paspalum at left is damaged by foot traffic at this busy course near Bangkok, while the manilagrass tee surface at right has much less traffic damage

Research conducted at the University of Arkansas has determined that manilagrass is more resistant to divots than are Cynodon species. In fact, divots from Cynodon species on average were almost 2x larger than were divots taken from manilagrass. So we can expect that there will be fewer (and smaller) divots on manilagrass tees. Another research project at the University of Arkansas found that some cultivars of manilagrass have divot recovery times equal to or faster than some cultivars of hybrid Cynodon. So we can have a situation with manilagrass of smaller divots to begin with combined with a recovery time very similar to Cynodon hybrids.

Turfgrass Nutrient Requirements and Fertilizer Choice

I made two presentations this week at the Sustainable Turfgrass Management in Asia conference. The slides and supplemental handouts from these presentations are available for download with links provided below.

The handouts for each talk are the most useful of these documents. Although the title of the first presentation is Nutrient Requirements of Tropical Turfgrass, the handout outlines a method that can be applied to any grass, at any location, to determine nutrient requirements.

This presentation makes use of the temperature-based growth potential (GP) of PACE Turf. After my talk, I was asked if there is a web-based service available for determining GP at one's location. There is not, but PACE Turf, in their IPM planning tools, provide Climate Appraisal Forms that have the growth potential equation embedded and are an easy way to introduce oneself to these calculations.

The second presentation is entitled What Fertilizer Should I Use? The accompanying handout explains how expected nutrient use of the grass can be compared to soil nutrient levels to determine exactly how much, and of which elements, should be applied in order to keep the nutrient availability at or above the minimum levels for sustainable nutrition (MLSN) guidelines.

Handout: Nutrient Requirements of Tropical Turfgrass, 5 page PDF

Handout: What Fertilizer Should I Use, 4 page PDF

Shade and the Performance of Warm Season Grasses in Asia

Have a look at this image. It is an aerial view of Wack Wack Golf and Country Club, a 36 hole golf course in Manila. The West Course is on the left side of the image, and the East Course is on the right side. Do you notice a difference in the grasses?

View Larger Map View Bird's Eye

To me, the grass on the East Course looks greener and healthier than the grass on the West Course. And the grasses are different. The East Course has broadleaf carpetgrass (Axonopus compressus) fairways and manilagrass (Zoysia matrella) greens; the West Course is all hybrid bermudagrass.

Trees on the East Course (see below) throw shade everywhere, but the carpetgrass and manilagrass still thrive in these conditions. The bermudagrass does not.

This case study on The R&A's Golf Course Management site provides more details and photos about the benefits of using native grasses at Wack Wack. The aerial view shows just how well those native grasses perform in that environment.

Just down the road at Manila Golf Club, there is some incredible shade thrown across the course each morning by a row of 55 story buildings on the east side of the property.

In such heavily shaded conditions, manilagrass performs the best, then seashore paspalum, with bermudagrass (Cynodon) not doing well at all. In the photo below, I identify the manilagrass with my nose, and the bermudagrass test plots identify themselves - they are basically dead. 

In tree shade or in building shade in Southeast Asia, manilagrass performs exceptionally well as a fine turfgrass. But there is another type of shade, one that can block up to 75% of photosynthetically active radiation. That is the shade that comes from clouds. 

Last week, I took this photo at 10:51 in the morning. The sun was behind a cloud and the quantum meter has a reading of 498 micromoles of photosynthetically active light per square meter per second. That is less than 25% of full sunlight. The effect of clouds is not terribly important for cool-season grasses, and most textbooks ignore it, but this is a big issue for warm-season grasses.

I've studied and written about this and its relevance particularly to the conditions so common in East and Southeast Asia.

Click here to download How Much do Clouds Affect Photosynthetic Irradiance? Measures of Light at Thailand, Hong Kong, Vietnam, and Japan

From Indonesia in the south to Japan in the north, we see that manilagrass, and in the areas with average annual temperature above 22°C, carpetgrass as well, perform extremely well. Particularly in shaded conditions, which can be caused by trees, buildings, or clouds, these grasses outperform bermudagrass and seashore paspalum. 

An Exemplary Guide to Control of Turfgrass Diseases

One of the best guides to control of turfgrass diseases is this one: Chemical Control of Turfgrass Diseases 2013 by Dr. Paul Vincelli and Dr. Gregg Munshaw from the University of Kentucky. 

In just 24 pages, this guide covers it all. And it is free! Topics covered include:

• Contact and systemic fungicides
• Preventative and curative use of fungicides
• Details on more than 40 fungicidal and biological control products
• Advice on cultural methods to reduce disease
• Management recommendations for more than 25 turfgrass diseases
• Links to additional information

This is a document that I use for reference throughout the year and I have now updated my files with the 2013 version. If you find it as useful as I do, you should do the same. Download it here.

Another turfgrass disease reference that I use frequently is the Compendium of Turfgrass Diseases. 

Related articles

Soil and Water Testing for Turfgrass: valuable tool, or absurd pretense?

Turfgrass Fertilizers: an exemplary fact sheet

Turfgrass Mystery: how was this bunker revetted?

Sand, Sodium, and Soil Structure

Sand rootzones are common the world over for golf course putting greens. Many athletic fields are also built with a sand rootzone, and in Asia, many of the tees, fairways, and even roughs are grown in a sand rootzone. Is sodium a problem for structure of these soils? The answer is a resounding NO. 

From the chapter Warm-season Turfgrass Fertilization by Snyder et al. in the Handbook of Turfgrass Management and Physiology, we learn that the "very sandy soils that often are used for golf greens and athletic fields have no structure and are largely unaffected by sodium."

Research presented at the 2012 Crop Science Society of America Annual Meeting by Obear et al. also showed that extremely high levels of sodium have no effect on the saturated hydraulic conductivity of sand rootzones. In this paper, Effect of Sodium On Saturated Hydraulic Conductivity of Sand-Based Putting Green Root Zones, sand, sand with various amendments, and a silty clay loam, were saturated with waters of varying sodium levels. The saturating solution with the highest amount of sodium had a sodium adsorption ratio (SAR) of 80, which is extremely high. 

But when the saturated hydraulic conductivity of the soils was measured, none of the sands, even those with the highest amounts of sodium, had a decrease in water movement through the profile. 

There are a few reasons to pay attention to sodium. In soils with appreciable levels of clay, soil structure can be negatively affected by sodium. If rapid blight is a possibility at one's property, then the soil sodium should be kept at less than 110 ppm. And one should be aware of the electrical conductivity (EC_w) of the irrigation water and of the soil (EC_e). Sodium can be a major contributor to that, and if the EC_e approaches the threshold level for a species, steps should be taken to manage the soil salinity.

But sodium and soil structure in sand rootzones? That is not something to be concerned about.

The R&A Holing Out Test: measuring the probability of making a putt

The R&A Holing Out Test is conducted by rolling 10 golf balls in a direction and at a pace so that the ball should, if the roll is not disrupted by irregularities, fall into the center of the hole. From the number of the balls that actually do fall into the hole, out of 10, one can get some idea of the smoothness, trueness, or reliability of the putting surface. This video gives an introduction to this test and shows balls being rolled from the Greenstester. 

This is an exciting new measuring tool that I just started using this week. The stimpmeter is one thing, and it is interesting to know the green speed. A Clegg Hammer or Tru-firm or Yamanaka Tester is interesting also, to get a measure of green hardness. The R&A Holing Out Test is an important addition to the evaluation of putting green performance, because it allows us to measure something that is very related to the game.

If we make a perfect stroke, is the green reliable enough that the ball will go in in the hole? The stimpmeter reading and the green firmness reading don't even attempt to answer that, but The R&A Holing Out Test does.

Putting greens that are reliable, meaning that the ball goes where it is intended, are sure to reward good putters with more birdies. I, for one, am excited about that prospect.