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March 2013

Nutrient Supply and Plant Species Diversity

On March 28 (or March 29 in Asia), Episode 23 of the Turf Diseases Turf Chat will be on the subject of Soil Nutrients and Weed Management. This promises to be an interesting discussion, led by Dr. Scott McElroy from Auburn University and hosted by Dr. Larry Stowell of PACE Turf.

It is a well-known phenomenon that application of nitrogen favors grasses and reduces species diversity (i.e. reduces the number of weedy species), while increasing the soil pH through addition of lime, and adding potassium fertilizers, as an example, can increase the prevalence of weeds. In a brief exchange on twitter last week, we discussed this, and decided to make this subject the focus of the upcoming Turf Chat.

Dr. McElroy says that this phenomenon is already known, while I would argue that despite it being noticed more than 150 years ago, and the mechanisms of this worked out more recently, among turfgrass managers, there is not universal knowledge of these principles.

Woods_rossi_park_grassThat was the subject of an article I wrote with Dr. Frank Rossi from Cornell University about the Park Grass Experiment and some of the results from this classic experiment, especially the noted absence of dandelions from plots to which potassium fertilizer is withheld.

For more detail about this, please read our article about Park Grass from the Green Section Record, and you can find a list of references at the end of that article for additional reading. Of particular interest may be this one, by Silvertown et al., The Park Grass Experiment 1856-2006: its contribution to ecology.

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

20030324_woods_k_field_experimentTen 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!

Woods_cornell_snow_mold_april_2003I 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.

Waterfall Chart of Putting Green Sodium Levels

I have decscribed how a waterfall chart can be used to show the nutrients that enter and leave a system, using potassium as an example. In that example, I did not show any input of potassium from irrigation water or rainfall, because I made the assumption that those inputs would be negligible. David Kuypers, the Golf Course & Grounds Superintendent at Cutten Fields in Guelph, Ontario, asked what would happen with sodium (Na) added through irrigation water:

That is an excellent question, and this chart for Na shows what may happen with that element. Na-waterfall-chartLet's look at a few components of this waterfall chart.

  1. The horizontal blue line at 110 ppm marks the MLSN guideline for Na. Unlike the 35 ppm level for K, which is a minimum guideline, this 110 ppm maximum guideline for Na is related to increased chance of rapid blight disease at soil Na concentrations above 110 ppm.
  2. I assume that we start with a Mehlich 3 extractable Na of 75 ppm. The annual plant uptake of Na is minimal for cool-season grass and I estimate it as being equivalent to a decrease in soil Na of 5 ppm. 
  3. I assume no Na is added as fertilizer.
  4. David said that his irrigation water has an average Na concentration of 110 ppm. That means for each liter of water, there are 110 mg of Na. If he adds 205 mm of irrigation water to the greens over the course of the season, that is equivalent to 205 L of water for each square meter. If we assume that the 22,550 mg of Na contained in those 205 L of irrigation water are distributed throughout the top 10 cm of the rootzone, and that the bulk density of the rootzone is 1.5 g/cm3, then that amount of Na will increase the Na in the system by 150 ppm.
  5. With this depiction on the waterfall chart, we can see that the amount of Na expected to be added with this much irrigation is twice the amount of Na that was in the soil at the start of the year. And we can make some comparison of the magnitude of each input and loss of Na from the system.
  6. However, sometimes there will be thunderstorms or other heavy rain events that will cause some leaching of that Na. Most of that Na will be remaining in soil solution; it won't be extensively held on cation exchange sites which would make it resistant to leaching. And if rain doesn't come, I assume that David will sometimes apply extra irrigation water to induce leaching of the Na. I assume that 130 ppm of the Na will be lost by leaching.
  7. With these assumptions, that leaves us at the end of the year with 90 ppm of Na in the soil, still below the 110 ppm MLSN guideline. And if we would go through the fall, and through the winter, we would expect no irrigation water to be applied, and some leaching to occur, and by the start of the next irrigation season, the Na would be reduced even more. In an arid climate, the Na would be expected to increase and increase, but in a humid climate, one in which precipitation exceeds evapotranspiration, most of the applied Na is expected to leach.
  8. We can see that if no leaching occurs, the addition of Na through irrigation will increase soil Na above the MLSN guideline of 110 ppm.

For more about maintaining soil Na below 110 ppm, see this document from PACE Turf.

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.

SnowGolf 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.

Presentation Slides and Handouts from Thailand Conference Available for Download

The presentations slides and handouts from the Sustainable Turfgrass Management in Asia 2013 conference are now available for download. Delegates to the conference – there were 242 in total, from 20 countries! – received this information in their seminar books and on CD, and we make these materials available online for those who were not able to attend the conference.

With information on a range of important topics, from maintenance equipment to fertilizer choice, irrigation management to recovery from flooding, and much more, you will be sure to find something of interest in these educational materials.

And these materials, although developed specifically for this conference, are in many cases applicable to anywhere in the world. As an example, you can look at my guide to estimating nutrient requirements which is applicable to turfgrass grown anywhere, John Neylan's superb presentation and handout on Irrigation Management - Making the Most of Your Water, and Dominic Wall's presentation on Setting Up a Golf Course for a Championship. And the slides from Kittipong Haranrat's presentation about recovery from the devastating floods that hit central Thailand in late 2011 have some great information about flood recovery, along with amazing photos of the flood.


Using Waterfall Charts to Look at Soil Nutrient Levels: potassium as an example

6I have recently described a method that can be used to estimate nutrient requirements for any turfgrass, grown at any location. This method makes use of the temperature-based growth potential and the minimum levels for sustainable nutrition (MLSN) guidelines.

This method makes a few basic assumptions about turfgrass management.

  1. The soil can hold a fixed amount of nutrients; it cannot hold an unlimited amount.
  2. The plant takes up a limited amount of nutrients; the plant does not take up an unlimited amount.
  3. Application of more nutrients than the soil can hold, or than the plant can take up, provides no benefit to the grass, nor to the soil, and is in fact inherently wasteful.

This is essentially a mass balance approach, in which we consider the rootzone and the turfgrass as a system and we account for the nutrients that enter and leave that system. We can use a waterfall chart to visualize the individual and cumulative effects of the nutrient addition and the nutrient loss from our turfgrass and rootzone system.

This type of chart is described on Wikipedia as:

The waterfall chart is normally used for understanding how an initial value is affected by a series of intermediate positive or negative values. Usually the initial and the final values are represented by whole columns, while the intermediate values are denoted by floating columns. The columns are color-coded for distinguishing between positive and negative values.

Let's look at potassium (K) as an example, developing the chart step-by-step. I first make a frame for the chart. I've labeled the y-axis with K expressed in units of ppm (mg/kg).


Next, I draw a horizontal line, in blue. 


This line is at 35 ppm, which is the MLSN guideline level for K. What the MLSN guideline means, in simple terms, is that we have a high level of confidence that turf will perform well and will have access to ample amounts of an element, as long as the soil level remains at or above the MLSN guideline. For K, we are confident that the turf will perform well and will have access to ample K when the soil K, as measured by the Mehlich 3 soil test extractant, is at or above 35 ppm.

Then I add on a column to represent the amount of K actually in the soil, as determined by a soil nutrient analysis. In this example case, the soil test value is 70 ppm. This is a typical value for Mehlich 3 K in a sand rootzone. Note that this is more than the 35 ppm MLSN guideline, and we consider this soil test level as our starting point. Any positive amount of an element, or an addition of that element to the system, I will represent with a black color. Any loss of an element from the system will be represented in red.

Next I add a column for annual plant uptake. This is based on the assumption that leaf clippings will be collected and removed from the system. This removes whatever elements are in the leaf clippings, including K. We can note a few things here:

  1. The color of the "Annual Plant Uptake" bar is red, meaning this is a loss of K from the system.
  2. ­­­‒54 is shown at the bottom of the bar, which indicates 54 ppm of K is estimated to be lost from this system by annual plant uptake.
  3. 54 ppm is equivalent to 8 g/m2 (or 1.6 lb./1000 ft2) when expressed on a mass per area basis, and this assumes average rootzone depth of 10 cm and a soil bulk density of 1.5 g/cm3.
  4. This amount of annual uptake and removal from the system is what we would expect when average leaf K content on a dry matter basis is 2% and when the annual dry matter clipping harvest is 400 g/m2. This would be typical of creeping bentgrass greens in a climate such as Tokyo or New York.
  5. Notice that if we simply combine the soil test level at the start of the season, which is 70 ppm, and then account for the annual plant uptake, wich is estimated to be 54 ppm, then we drop the amount of K in the system to less than the MLSN guideline, all the way down to 16 ppm.


But we don't want the K to drop below the MLSN guideline. To prevent this, some K will be applied as fertilizer. Let's look at the chart now that the "Fertilizer Applied" column has been added.

  1. The "Fertilizer Applied" column is in black, indicating that this is an addition of K to the system.
  2. The amount added, 67 ppm, is equivalent to 10 g/m2 (or 2 lbs/1000 ft2). This assumes the K is added to the top 10 cm of the rootzone and that the soil has a bulk density of 1.5 g/cm3.
  3. Notice that the Soil Test column has a length of 70, the Annual Plant Uptake column has a length of 54, and the Fertilizer Applied column has a length of 67. This is useful in comparing the magnitude of the amounts in the system. The amount of Fertilizer Applied is greater than the amount of Annual Plant Uptake, and the Fertilizer Applied is similar in amount to the level of K in the Soil Test at the beginning of the season.
  4. The amount of K in the system, because of the K addition through fertilizer, has now increased to above the MLSN guideline of 35 ppm.


To complete the chart, I add a final column, to show the amount of K "Remaining in Soil". This column has a length of 83, showing that there is 83 ppm of K in the system. This is 70 minus 54 plus 67. And it indicates that when we have a starting level of 70 ppm of K in the soil, with a harvest through plant uptake of 54 ppm, and a fertilizer addition of 67 ppm, then we expect to have 83 ppm of K remaining in the system (in the soil) and that this level is well above the MLSN guideline.

I find this to be an interesting graphical approach to depicting soil nutrient levels and their relationship to the MLSN guidelines. If we would look at nitrogen, or calcium, or magnesium, or phosphorus, using this approach, we can understand more clearly how the amount in the soil is related to the plant uptake, and how that helps to determine the annual nutrient requirement as fertilizer.

Turfgrass Nutrient Requirements and Fertilizer Choice

WoodsI 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

Two Excellent Articles: course maintenance standards and bermudagrass green edges

Niven_value_maintenance_standardsThis week's issue of the USGA Green Section Record has two articles that I really enjoyed reading. One, by MacDonald Niven, explains the value of course maintenance standards and give links to many resources that can help in the development of standards for your club. I've written about maintenance standards before, and I've spoken about their value at various seminars, but Niven explains their value much better than I ever have. He summarizes the key benefits:

  • organizing and analyzing priorities for golf course maintenance
  • developing an accurate budget to support desired standards
  • the maintenance standards document becomes an effective communication tool to share with golfers, decision makers, and the community
  • written maintenance standards eliminate emotion and subjectivity when evaluating the effectiveness of the maintenance department

I have sometimes described maintenance standards as being essential because they define what the course maintenance department is actually trying to achieve. The work can be done most efficiently if we know exactly what type of conditions we are trying to produce.


Another article gives an excellent and novel technique (at least to me) for reclaiming bermudagrass putting green edges that have been contaminated by another type of grass. Todd Lowe has written some excellent articles that I have highlighted before, on off-types in ultradwarf greens and on new trends in ultradwarf putting green management, and this one, Reclaiming Putting Green Edges Using Core Aeration Plugs, is a must-read for anyone who manages warm-season putting greens.

Lowe-reclaiming-3-8-13Lowe writes that "plugging perimeters with aeration cores offers a practical solution to encroachement of rough-type bermudagrasses into bermudagrass putting greens." After reading the article, I believe that this method can be used not only with bermudagrass greens, but also with seashore paspalum greens or manilagrass greens. The method involves identifying the original green edge, killing the encroaching grass with a non-selective herbicide, removal of the contaminated turf with a sod cutter, and then core aeration of the greens with the cores being pushed into the prepared areas at the green perimeter. 

The USGA Green Section Record is a great source of turfgrass information and is available with a free subscription.

Slides and Handout from GCSAA Paspalum Webcast

On 7 March, I taught a webcast for the Golf Course Superintendents Association of America (GCSAA) entitled Today's Turf is ... Paspalum.

Paspalum_gcsaa_handoutThe GCSAA has made these slides and the three page handout available for download.

In the webcast, I discussed the two main reasons for using seashore paspalum (Paspalum vaginatum): the excellent salinity tolerance of the grass and its beautiful visual appearance. I also showed where we find seashore paspalum growing in the wild, which has some implications for how we might best manage the grass on golf courses. And I discussed some of the challenges we face in producing fine seashore paspalum surfaces, specifically talking about dollar spot disease and bermudagrass (Cynodon) weed problems.

The GCSAA makes these webcasts, available on a range of topics sure to be of interest to golf course superintendents, free to their members the world over. This is just one of the many benefits of GCSAA membership