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July 2013

Something you don't see everyday: interveinal chlorosis on grass leaves

interveinal chlorosis caused by micronutrient deficiency

Nutrient deficiencies of turfgrass are rare. Macronutrients are usually supplied as fertilizer in amounts that prevent deficiencies, and micronutrients are required in such small amounts that the grass can usually obtain all that are required from the soil, from micronutrients contained in the irrigation water, and from trace amounts contained in various products.

These photos show textbook symptoms of interveinal chlorosis, probably caused by iron deficiency. The leaves have turned yellow, but the veins remain green. This is tropical carpetgrass (Axonopus compressus) grown in sand. The symptoms are especially evident on this grass because of the broad leaves. Click the photos to see a full-screen image.

interveinal chlorosis of Axonopus compressus

Influence of Phosphorus on Annual Bluegrass Encroachment in a Creeping Bentgrass Putting Green

Its_vol2_coverIn yesterday's mail I received a big package containing the International Turfgrass Society Research Journal Volume 12, which stretches to 848 pages, and that is before the subject and author indices! This book contains the papers presented at the International Turfgrass Society Conference held this month at Beijing.

I didn't attend – various other travel in the past month saw me fly on Boeing 787, 777, 767, 747, and 737s, as well as bullet trains, rapid trains, express trains, and local trains, along with innumerable ferries, buses, taxis, and private vehicles, so I was not anxious to travel any more – but the contents of the journal have left me ensorcelled, and I will share some of my favorite articles here over the next few weeks.

The paper I was most excited to read was this one, Influence of Phosphorus and Nitrogen on Annual Bluegrass Encroachment in a Creeping Bentgrass Putting Green, by Raley et al. Some of the highlights, which I will quote from the paper:

Changes in annual bluegrass cover due to P treatment were detected on all evaluation dates. Annual bluegrass cover always increased, relative to the pre-treatment population, in plots treated with P versus those in which no P was applied.

Increased levels of P in the current study had no effect on clipping yield

Tissue P concentrations above those found in the [no P applied] treatment tended to show greater annual bluegrass cover

Results of this study demonstrate that annual bluegrass encoachment into a newly established creeping bentgrass putting green can be curtailed by withholding P fertilizer such that soil P concentrations and P uptake are below levels that foster the competitive ability of annual bluegrass.

After 2 years of treatments, soil Mehlich 3 phosphorus concentrations were positively correlated with changes in annual bluegrass cover; treatments producing concentrations ≥ 13 ppm had greater annual bluegrass cover than those measuring < 13 ppm.

An annual bluegrass plant

Kreuser et al. found a similar level of soil P to be adequate for creeping bentgrass, and the MLSN guideline level of 21 ppm, developed using a robust method to evaluate thousands of soil samples from good-performing turfgrass sites, is similar to the 13 ppm threshhold identified by Raley et al. 

This is another indication that conventional guidelines (usually in the range of 45 to 75 ppm, more than 3x the MLSN guideline) are targeting a higher level of soil P than is necessary.

For more about this, see:

How much phosphorus does grass require?

Fertilizer and Weeds at Park Grass

How much potassium does grass require?

Turfgrass Interview: Fairways of Life on the Back9Network


Yesterday I spoke with Matt Adams on his Fairways of Life show, broadcast on the Back9Network and SiriusXM's PGA Tour Radio.

07.09.13 INT ARCHIVE Fairways Of LIfe Micah Woods_3592772

Click the play button above to listen to interview, or watch a video (my interview starts at 55:30) on the Back9Network. We talked about how to choose grasses that use less water, and what I am really excited about in ways to use less water and improve playability.


You may also like to listen to this interview from last year, when I spoke with Chicho Morales on Bajo Par Canarias. My comments start at about the 10 minute mark.

Turfgrass Mystery: what happened to this green?


This is a MiniVerde ultradwarf bermudagrass green in the western part of Japan.

These photos were taken on 1 and 2 October. For a closer look at the grass, click on the image below:


At this location, the average air temperature for the previous three months had been 27.7°C in July, 30.3°C in August, and 26.3°C in September. Those are almost optimal temperatures for the growth of ultradwarf bermudagrass. It rained a lot in July, 454 mm, and then August and September saw 70 and 139 mm of rain, respectively.

In the worst area of the green, it looked like this:


However, it would seem that the weather in the preceding three months had been almost ideal for the growth of ultradwarf bermudagrass. 

The mystery is, what happened to make the green look like this? 

Here is one more photo. In the foreground is the mysterious MiniVerde green. In the background is a manilagrass (Zoysia matrella, called korai in Japan) green, that seems to be fine by comparison.

This was a tough mystery to solve, with many guesses, ranging from disease, to localized dry spot, to salt damage, to scald from hot topdressing sand, and many more. This damage was actually caused by application of the fungicide tebuconazole. I don't usually expect to see fungicides having this effect on grass, so I found this a difficult mystery to solve myself. Here is the correct answer.

Thanks to everyone who helped to solve this. I have seen damage, sometimes severe, on ultradwarf bermudagrass greens in multiple countries in Asia after they have been sprayed with DMI fungicides (such as propiconazole or tebuconazole) at the label rate. Difenoconazole is supposed to be safer. For more information about DMI fungicides and bermudagrass greens, see this article by Dr. Monica Elliot: Bermudagrasses vulnerable to injury from some DMI fungicides.

In this situation, the tebuconazole damage was compounded by uneven application of the product. In the photos above, one can see various patterns of heavy or light application. The application method was similar to below, using a tanksha sprayer and applying the product with a hand wand.

I should give some partial credit to these responses also, for correctly identifying that the application method applied a product unevenly.


Looking back to a July with record heat and drought

Habu CC 10 green

Twelve years ago this month, I was the greenkeeper at Habu CC in Chiba prefecture, near Tokyo. I was recently looking at some photos of the course from that month, and reminiscing on the hard work of golf course maintenance that summer. I remember that it was hot, and that we had to irrigate a lot, and that I or one of the interns or employees would have to go to the course every night to check if the irrigation system was working properly.

Today I wondered just how hot and dry it was that month. So I looked it up. The most extensive set of data near Habu CC are from the Chiba station, with data for 47 years, from 1966 through 2012. I have made a few plots to show these data.

July 2001 matched the previous record monthly average temperature, and that record was only broken in 2010. This chart includes a red line with the average for all 47 years, and the data for 2001 are shown in a green square. The mean July temperature in 2001 was more than 2.5°C above the long-term average.


At the time, July 2001 set a new record for average daily high temperature, breaking the previous record by almost 1°C, nearly 4°C above the long-term average. That record was broken in July 2004.


Combined with the record-setting heat, I was surprised to discover that it was the driest July on record, with only 8 mm of precipitation, less than 10% of the long-term average.


I remember that we worked hard that summer, but at the time, I did not realize that we were working through record heat and drought. Thanks to the fine records of the Japan Meteorological Agency, I now have a better idea of how that month compares to a typical July. And with that knowledge, I am especially grateful to the fine greenkeeping staff from that summer – a third of whom have gone on to become golf course superintendents themselves – who worked so hard to maintain these conditions through that record-setting heat and drought. 

Habu CC 14 tee

Monthly Turfgrass Roundup (June 2013)

In case you missed them, these articles and links from June are likely to be of interest to turfgrass managers in Asia:

To understand turfgrass nutrient requirements and how grass will respond to fertilizer, one must understand just what it is that controls nutrient demand. Kussow et al. explained this in Evidence, Regulation, and Consequences of Nitrogen-Driven Nutrient Demand by Turfgrass.

I wrote about temperature-based turfgrass growth potential and explained how one can use growth potential to derive an estimate of grass nitrogen use. Download the guide here: Using temperature to predict turfgrass growth potential (GP) and to estimate turfgrass nitrogen use.

Greg Evans, MG, on the Ealing Golf Course Aronomy Blog, wrote about the results seen after implementing the growth potential method. He explained in detail what has been done, and how it compared to last year. "Our conclusions so far are very positive. We have used less fertiliser ... but our performance was better."

At the US Open, Dr. John Kaminski captured this great image of USGA agronomist Darin Bevard with a stimpmeter in the rain.

PACE Turf put together this chart looking at rain amounts during the week of June 7 to 14 (US Open week) in Philadelphia for the past 20 years. Was the rain that fell in 2013 usual, or unusual? The chart makes the answer pretty clear.

In Philadelphia, cool-season grasses are typically used for golf courses. In Seoul, where the average temperatures through the year are almost identical to Philadelphia, the warm-season grass Zoysia japonica is in common use. Why? I suggest that even though the temperatures are similar, the shockingly different timing in rainfall between these two cities creates a difficult environment for cool-season grass in Seoul.

Keith McAuliffe wrote about how to get more play through better drainage in a new My View piece on The R&A's Golf Course Management page.

Don't Take Your Vitamins was the headline in the NY Times. Large quantities of supplemental vitamins can be quite harmful indeed. If there is already enough of something, ingesting more may cause more harm than good. Shouldn't we take the same care with turfgrass? The MLSN guidelines are a good place to start.

Dr. Rick Brandenburg created this funny (but important) video about snake oils and how to evaluate their effectiveness.

I wrote about making using of nutrients in the soil, showing through a graphical approach how the amount of available calcium and potassium in the soil is related to annual plant use and consequently to fertilizer requirement (or not).

The GCSAA announced a new webcast series for the upcoming months. I'll be teaching about Nutrient Use and Requirements on 24 October. You can register for the webcast here

I taught about irrigation management in summer at a seminar in Osaka. The handout from the seminar is available for download in English and in Japanese.

I wrote about summertime syringing to cool bentgrass greens, and why I would not do it today. This post (and the Twitter discussion that prompted it) drew a lot of attention, with some agreeing, and others vehemently opposed. What do you think?

Rather than attempting to cool grass through syringing, which I consider to be a spurious effort, I suggest maintaining the optimum level of plant-available water in the soil.

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An Invitation to the Philippine Turfgrass Forum


I am excited to be a part of the upcoming Philippine Turfgrass Forum, organized by Dr. Amihan Arquiza from University of the Philippines Los Baños (UPLB). The Forum will be held at UPLB on 1 August, with Dr. Arquiza and Tomas Valencia as the other keynote speakers.

My talk on minimum nutrient requirements of putting green turf will introduce the MLSN guidelines and the temperature-based turfgrass growth potential with an explanation of how this system can be applied to golf course putting greens and to other turfgrass areas. I will explain how to ensure the grass is supplied with enough nutrients to produce the desired surface, while avoiding application of unnecessary nutrients. I will also share five easy ways to improve turfgrass performance, based on extensive study of turfgrass conditions and maintenance practices in Southeast Asia.

The Forum is open to the public with advance registration required.