Tropical carpetgrass part 2: ugly duckling or swan?

When I wrote about tropical carpetgrass being an unappreciated grass, the conversations (1 & 2 & 3) that ensued showed a mixed response. Some people really like tropical carptegrass (Axonopus compressus), and others have no use for it.

Tropical carpetgrass on a golf course fairway in Singapore

It was rightly pointed out that in a a subtropical environment, tropical carpetgrass will not be ideal throughout the year, especially when it is cool. And like other grasses, there will be issues with drought tolerance, and traffic damage, and so on. Where this species is really well-adapted is in tropical climates that receive more than 1,000 mm annual precipitation; one wouldn't want this grass where precipitation is less than 800 mm. It is not a perfect grass, even in the tropics, but no grass is.

Tropical carpetgrass through the green at Chumpon, Thailand

So why do I persist in writing about tropical carpetgrass? Because for many tropical sites, this is the grass that should be used, and it has some very attractive characteristics that are especially relevant to the way I think about turfgrass management. When possible, I think we should manage turf with a minimum amount of inputs. Tropical carpetgrass, more than other species, can be maintained as a multipurpose turfgrass with the fewest inputs.

Last year I was interviewed by Matt Adams on the Fairways of Life radio show. You can listen to the interview here.

07.09.13 INT ARCHIVE Fairways Of LIfe Micah Woods_3592772

I was expecting Matt to talk with me about tournament preparation and golf and grasses around the world. Instead, he started by asking about maintenance inputs and grass selection:

Today more and more, there is pressure upon every golf facility in terms of how they maintain the golf course – the general line that we're hearing is that golf courses need to embrace more of the brown because water is at such a premium anywhere and everywhere around the world.

Then he asked, how can the type of grass chosen help us out in terms of maintainenance cost and availability of water? Rather than talking about using more resources and spending more money, the focus at the global level is to use less resources in turfgrass maintenance. 

This was also a prominent theme of Don Mahaffey's recent conversations at Golf Club Atlas (first interview, second interview). These are really good discussions about what golf course maintenance should be about, and I highly recommend taking the time to watch both of them in their entirety. In the second video, Don said something that is very applicable to turf management: 

We cut our maintenance expenses greatly, because we just focused on what's good for golf, and interestingly, no one complained.

Tropical carpetgrass fairway at Phuket, Thailand

With tropical carpetgrass, in a tropical climate with annual precipitation of at least 800 mm, and preferably with 1,000 mm or more, this grass requires only mowing. It can be maintained without fertilizer or pesticides, and irrigation is only required if one wants to make the grass green, or if the turf is to be heavily trafficked with golf carts.

There will be many golf courses or turf managers that prefer to grow and manage a grass that has different characteristics. But let's not forget about the many good characteristics of the multipurpose tropical carpetgrass. As the recent research from Trinidad and Nigeria demonstrates, this species has a number of advantages compared to other turf species in a tropical environment.

Tropical carpetgrass lawn in Ayutthaya, Thailand

Spots of excitement in a boring experiment

Doug Soldat reports on snow mold and potassium in this article. First he describes the study:

In 2011, we began a trial to attempt to identify the lowest level of soil potassium that would still provide high putting green quality. We also wanted to create severe potassium deficiences to document those symptoms for teaching purposes.

Treatments include 3 rates of potassium fertilizer, a control with no potassium, and a gypsum treatment with no potassium – adding gypsum will accelerate decreases in soil potassium. This is all on a sand rootzone with low cation exchange capacity. But those potassium deficiencies haven't appeared yet:

Visually, this study has been about as boring as it gets. In three seasons, we have yet to observe any statistical differences in color, quality, or clippings.

This spring, however, after the snow melted:

It was clear that the [pink] snow mold damage was influenced by the potassium treatments. Treatments receiving no potassium were essentially free of damage, and treatments receiving 0.2 - 0.6 lbs K2O/1000 ft2 biweekly [1 to 3 g K2O/m2/14 days] had roughly 10 infection centers per plot, covering about 3.5% of the turf.


Increasing rates of potassium fertilizer reduce the leaf calcium content. I measured this in creeping bentgrass grown in a rootzone with a high calcium content. Increasing rates of potassium fertilizer reduced soil and leaf tissue calcium and magnesium.

This happens with warm-season grass too. Grady Miller measured decreased calcium and magnesium in bermudagrass:

Increasing K fertilization resulted in a decrease in extractable Ca and Mg in both media with corresponding decreases in tissue Ca and Mg concentrations. High K rates appear to increase the potential for Ca and Mg deficiencies in bermudagrass, indicating that rates higher than those that provide sufficient K levels for normal growth should not be used.

The mechanism by which pink snow mold was increased or decreased on the potassium experiment at Wisconsin hasn't been determined. Soldat suggests a possible reason for the potassium effect on disease, and gives some advice on how one might optimally manage potassium:

It is possible that the effect of potassium is to lower the calcium levels to a point where the plant becomes susceptible to fungal infection ... These findings suggest that the optimum way to manage potassium on a sand root zone is to allow the soil potassium levels to drop near the ... MLSN level of 35 ppm, then begin spoon feeding potassium in spring through summer, and stopping in August to allow the tissue levels to decrease and calcium levels to rise (which will happen naturally).

The greens here have never been better: on EIQ and pest management programs

This is one of those "if I were a greenkeeper today, this is how I would do it" type of stories.

At the Bethpage maintenance facility; research here demonstrates that use of EIQ can reduce environmental impact from 33 to 85% while producing the same quality turfgrass

I was pleased to read the update from Jason Haines about his use of the EIQ (environmental impact quotient) and the results he is getting. He reports that he is ahead on cost goals, ahead on EIQ goals, and that "the greens here have never been better." That sounds like a win-win-win situation.

The EIQ Field Use Rating based on formulation and application rate allow turf managers to identify and choose products based on their predicted environmental impact. From the New York State IPM Program, which administers the EIQ:

By using the EIQ model, it becomes possible for IPM [integrated pest management] practitioners to rapidly estimate the environmental impact of different pesticides and pest management programs before they are applied, resulting in more environmentally sensitive pest management programs being implemented.

Because of the EPA pesticide registration process, there is a wealth of toxicological and environmental impact data for most pesticides that are commonly used in agricultural systems. However, these data are not readily available or organized in a manner that is usable to the IPM practitioner. Therefore, the purpose of this bulletin is to organize the published environmental impact information of pesticides into a usable form to help growers and other IPM practitioners make more environmentally sound pesticide choices.

Jennifer Grant wrote about the use of EIQ Field Use Ratings in research projects at Bethpage State Park. The results there?

Using the Environmental Impact Quotient (EIQ) as the measure, impact was reduced on progressive IPM/alternative culture greens by 33%-85% compared to the conventional pest management/conventional culture greens — almost always without a loss in quality.

The EIQ incorporates the toxicological and environmental impact data for pesticides and makes it easy for turfgrass managers to compare the products they might use, allowing them to choose the one with a lower EIQ — a lower environmental impact.

MLSN, K, and anthracnose

In recent conversations (here and here), the topic of potassium (K) requirement for turf has come up, and there has been mention of the anthracnose research at Rutgers. There has also been concern about the "longterm impact" of using the MLSN guidelines.

What's the story here? One might summarize it in this exchange between John Kaminski and (I presume Larry Stowell of) PACE Turf

Kaminski: Now discussing the MLSN recommendations from @asianturfgrass and @Paceturf. Mixed feelings from group on longterm impact.

Stowell: What is the concern? MLSN maintains soil nutrients at the level required for good turf performance.

Let me explain why I'm confident the MLSN guidelines ensure the turf will be supplied with enough nutrients in the short term and the long term, and try to relate this to the recommendations from Rutgers.

1. If you haven't, please read the article explaining the MLSN guidelines in GCM Magazine. The MLSN guideline for K is 35 ppm. This means the soil K should be kept at or above 35 ppm.

2. 35 ppm K in the soil is equivalent to just over 1 pound of K per 1000 ft2 (5 g of K per m2). That is the reserve amount of available K in the soil, even when the soil test level is low and approaching the MLSN guideline for K.

3. K fertilizer recommendations using the MLSN guidelines estimate how much K the grass will use, and recommend application of 100% of that amount if the soil is at the MLSN guideline. To rephrase this, using the MLSN guideline for K, there is more than 1 pound K per 1000 ft2 remaining in the soil as a reserve, even when the soil approaches the minimum level, and the fertilizer recommendation ensures 100% of the K the grass will use is supplied.

4. For concerns about long term impact, the data used to develop the guidelines include only samples from good-performing turfgrass sites. And these are sites of all ages. Indirectly, the MLSN guidelines have already been evaluated for long term impact. While there may be concern at a particular site with high soil K about what might happen in the long term if soil K were to decrease at that site, I'm confident that as long as soil K is maintained at or above 35 ppm, the grass will be supplied with enough. There are thousands of sites around the world with high-performing turf in soils with K at or above 35 ppm.

5. Research at Rutgers shows that K addition to Poa annua putting green turf reduces anthracnose. To read more about this, see:

There is a clear effect of K in their research. They have collected a lot of data on soil and leaf K, and I am looking forward to more publications (and more data) about these experiments. But where there is a response to K applications, as shown in this chart from PACE Turf, is at soil levels at which we would be recommending K using the MLSN guidelines anyway. However, see below that the amount of K they apply to get an effect is much more than 100% of the grass use.

image from www.paceturf.org

6. The experiment at Rutgers in which the effect of K was seen received summer N at less than 33% of the amount recommended to minimize anthracnose. That is, the experiment designed to establish sufficiency ranges for K was done on turf maintained artificially low in N, presumably to encourage anthracnose. One wonders what the K effect would be on turf supplied with the recommended nitrogen rates.

7. The amount of K supplied in the Rutgers experiments was much more than the grass could use or the soil could hold. The K recommendations based on this are for application of N and K in N:K molar ratios of 2:1 or 1:1. Based on plant use of K, those recommendations supply K at rates from 280% to 560% of plant use on a mass basis.

8. The MLSN guideline for K ensures 100% of the grass K requirement will be supplied, by fertilizer or from available soil K, all while keeping more than 1 pound of K per 1000 ft2 in reserve. 

A Fortunate Stroke of Serendipity

Yesterday, while botanizing in Kanagawa prefecture near Kamakura, I saw Zoysia japonica near the ocean and Miscanthus sinsensis near Daibutsu.


On a headland at the end of Inamuragasaki Beach, I saw a bit more zoysia and what appeared to be a viewpoint in a grove of pine trees. I climbed up to the grove, and there I saw a monument. From a distance, I could see what appeared to be some text in English. 


I was surprised (and pleasantly surprised) to see that this monument was erected to commemorate the visit of Dr. Robert Koch to Kamakura in 1908. You will be familiar with Koch's postulates, the four criteria that establish a causative relationship between a pathogen and a disease. Click the image to see a larger view of the inscription. 

Identification & Management of Turfgrass Diseases

CoverThis guide is one that all turfgrass managers should have on their desk or in digital format: Identification & Management of Turfgrass Diseases. And it doesn't cost anything. It is a free download, as a 56 page full color PDF file.

Written by Barb Corwin, Ned Tisserat, and Brad Fresenburg, and published by the University of Missouri Extension, this guide begins with an overview of disease ID and control and proceeds to a 2-page section on each of the major turfgrass diseases.

I've found this guide especially useful, along with the Chemical Control of Turfgrass Diseases (also free!) by Vincelli and Munshaw.

If you want to see which turfgrass species are hosts to which diseases, or which fungicides can control which diseases, you will find that information in the opening pages.


Then comes a step-by-step guide to identifying diseases. After that are the 2-page summaries of each disease, covering Symptoms and Signs, Conditions under which the disease can occur, and Management.


In which I wrote a long answer to a short question about golf course grass in Rio de Janeiro

I've written this answer to a question I received last month about grasses for the Olympic Course in Rio de Janeiro.

The GEO Sustainable Golf Development Guidelines give a simple criterion for grass selection:

Sustainable grassing plans are based on the use of the most drought-tolerant and disease-resistant turfgrasses for the locality.

Read the question and my answer to learn more about expected performance of manilagrass and seashore paspalum.

Potassium + Dogma Might Increase Turf Problems

Last week I read two contrasting things about potassium and Microdochium nivale (fusarium patch or pink snow mold).

In the March Greenkeeper Internationalthis article about fusarium patch instructs one to:

Feed turf by all means - but with fertiliser formulations rich in potassium to make the most of the ‘gatekeeper’ nutrient with its intrinsic abilities in good water relations and strengthening of grass plant tissues.

There was also this, from Doug Soldat, showing an interesting result in which M. nivale was increased by potassium application:

When it comes to potassium application, one should not think that adding potassium will always "strengthen" the plant or improve resistance to diseases. Eliminating a potassium deficiency is almost always a good thing. Eliminating the deficiency will improve root growth, increase leaf growth, and ensure that the grass is able to function normally. Adding potassium beyond the amount required to eliminate the deficiency may cause problems.

  • dandelion increased by potassium application
  • snow mold increased by potassium application
  • foliar disease of bermudagrass increased by potassium application

Because too little potassium is problematic, and too much can also cause a problem, the approach to potassium fertilizer that seems most likely to optimize turf performance is this one - supply the potassium the grass requires, but only that amount.

It's here! Chemical Control of Turfgrass Diseases 2014

Ppa1_2014This reference guide by Paul Vincelli and Gregg Munshaw is updated for 2014 and is available for download from the University of Kentucky. 

Much more than just chemical control, the guide provides information on just about everything one might need to know about common turfgrass diseases, what may have caused the disease, and how it can be controlled. And there is a wealth of information about fungicides too. What is most amazing to me is that this much useful information can be delivered in just 24 pages! 

If you have already used this guide, you will want to get a copy of the 2014 version. And if you haven't used it, download it here. I think you will find it useful on more than one occasion this year.

Counting Down, Top 10 Posts of 2013 (#6 to #10)

Last year, the most viewed posts on this blog were all about fertilizer. This year, turfgrass nutrient topics were popular again, but a broader range of topics made it onto the list. Here are #6 to #10 on the 2013 list:

6. The Unambiguity of Turfgrass Nutrient Indicies 

7. Turfgrass Mystery on the Putting Green

8. Explaining the Turfgrass Growth Potential

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

10. An Exemplary Guide to Control of Turfgrass Diseases

I previously listed the 5 top posts from 2009, the top 5 from 2010, the top 5 from 2011, and the top 5 from 2012.

Coming up next week, I'll share the top 5 from 2013.