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April 2012

Turfgrass Mystery: what grass is this?

You may be surprised at the answer. What grass is referred to here? From an article by Charles Vancouver Piper, first chairman of the USGA Green Section:

"________ is the best of all grasses in the South for fairways. It makes a dense, uniform turf even on pure sands and the leaves are stiff enough so that the ball is always well off the ground. The only other grass to compete with it is Bermuda; but under conditions where both will grow, _________ makes far superior turf."

Please leave a comment here or reply on twitter with the answer. I'll post the answer and some descriptive photos in a few days. And here it is:

green fairway of Laguna Phuket

The grass Piper was referring to is broadleaf carpetgrass, Axonopus compressus. Read the article here, from the December 1921 issue of the Green Section Record. Thanks to Captain Ben Sims, Jason Chennault, Jim Prusa, Scott McVey, and John Dempsey who all gave the answer of carpetgrass or the genus Axonopus. At right, the beautiful carpetgrass fairways of Laguna National Golf Club in Phuket.

Other guesses pretty much covered the spectrum of warm-season grasses used on fairways: kikuyugrass, buffalograss, St. Augustinegrass, seashore paspalum, bahiagrass, centipedegrass, and zoysiagrass. 

Carpetgrass was a bit of a surprise to be mentioned in this way, and I received a lot of comments from people who said they don't like the grass. Perhaps in an area with a lot of sunshine, and a relatively high maintenance budget, bermudagrass would be a better choice. But there are a lot of areas in the world where carpetgrass thrives and provides the type of playing surface that no other grass can. Just yesterday, I played the famous course at Nuwara Eliya, on stunning carpetgrass fairways (note that these are Axonopus affinis, similar but not the same species as referenced by Piper). See below. 

At this course, the fairways are pesticide free. Weed-free too, except for a few other naturalized grasses that come in. And in the salubrious climate of Nuwara Eliya, the fairways are mown less than five times a month.


For more information, have a look at this photo gallery, read this article about Manila's Wack Wack Golf and Country Club, and see this article I wrote about C.V. Piper, who made the stunning statement about carpetgrass in the first place!

Turfgrass Disease Reference Guides

Last week at a seminar in Ho Chi Minh City, there was a question about how to choose which fungicides to apply to control certain turfgrass diseases. A reference that I find especially useful, because it is updated, packed full of information in only 24 pages, and is freely available from the University of Kentucky, is the Chemical Control of Turfgrass Diseases 2012 guide written by Paul Vincelli and David Williams.

Vincelli_chemical_control_turfgrass_diseases_2012.pdf (page 1 of 24)Another excellent and free resource is the NC State University TurfFiles website's disease section. For more general information about turfgrass diseases, the TurfDiseases website and associated Facebook page, twitter feed, and Google+ page are good places to find information. 

The book that I always keep handy is the Compendium of Turfgrass Diseases, 3rd Edition. This comprehensive guide covers the diagnosis and control of approximately 80 diseases and is packed with useful photographs of various warm- and cool-season turfgrass diseases.

A Wonderland of Grasses: Hawaii

Micah-lesThe climate of the Hawaiian Islands is such that a tremendous variety of grasses can grow well and produce fine turfgrass surfaces. I was recently at Hawaii to do some botanizing on the Big Island and on Oahu. Thanks are due to Les Jeremiah, CGCS, who helped guide me to some of the most interesting turfgrass sites; we visited fifteen distinct sites and made a quick survey of the grasses growing at each.

The species added up in a hurry! In just two days we saw:

  • Creeping bentgrass, Agrostis stolonifera
  • Bermudagrass, Cynodon dactylon
  • Hybrid bermudagrass, C. dactylon x C. transvaalensis
  • Broadleaf carpetgrass, Axonopus compressus
  • Narrowleaf carpetgrass, Axonopus affinis
  • Kikuyugrass, Pennisetum clandestinum
  • Manilagrass, Zoysia matrella
  • Japanese lawngrass, Zoysia japonica
  • Seashore paspalum, Paspalum vaginatum
  • Hilograss, Paspalum conjugatum
  • St. Augustinegrass, Stenotaphrum secundatum

North-shoreWe saw what was growing in the sun, what was growing in the shade, what grows under irrigated conditions, and what grows where no irrigation is applied. There is a striking contrast in grass species performance between the relatively sunny climate at Honolulu (at right) and the much cloudier conditions at Hilo (top right). At Hilo, even in full sun, we saw a lot of carpetgrass and manilagrass and very little bermudagrass. In full sun at Honolulu we saw a lot of bermudagrass and much less manilagrass or carpetgrass. And naturally, in unirrigated areas, we saw lots of bermudagrass, and very little seashore paspalum. 

Here is a collection of images showing these grasses and their distinctive appearances.  

Five Articles Every Greenkeeper Should Read

ReadThere are some articles about turfgrass management that I find myself referring to again and again, using as a reference, and making suggestions to turfgrass managers based upon the information in the articles. I've found these five articles quite useful, and if you haven't read them, you will find them to contain plenty of useful information.

Aeration and Topdressing for the 21st Century, by Pat O'Brien and Chris Hartwiger: this article from the Green Section Record gives recommended amounts of annual sand topdressing for different grass types

Cultivating to Manage Organic Matter in Sand-based Putting Greens, by Josh Landreth, Doug Karcher, and Mike Richardson: this article from the USGA's Turfgrass and Environmental Research Online publication shows that scarifying the surface removes more organic matter from the green than does coring, and suggests that coring should be done with tines spaced as close together as possible for maximum effect.

Soil Fertility and Turfgrass Nutrition 101, by James Baird: this article from the Green Section Record gives, in eight concise pages, a thorough review of turfgrass nutrition.

Interpreting Turfgrass Irrigation Water Quality Test Results, by Ali Harivandi: this publication from the University of California gives you all the information you need to understand an irrigation water test. It has plenty of technical detail and useful tables for interpretation and reference, but it all fits in eight easy-to-read pages.

Improved Overseeding Programs 1. The role of weather, by Wendy Gelernter and Larry Stowell: this article was publiched in Golf Course Management and has a somewhat misleading title, for it is about a lot more than overseeding. This article explains the growth potential concept, giving a method for simple calculations of probable turfgrass growth rate for both warm- and cool-season grasses, based on the optimum temperatures for growth. The use of growth potential can be extended to fertilizer requirements, aerification timing, disease pressure, and mowing frequency, among many others.

Want to read more? Here are Five More Articles Every Greenkeeper Should Read.

A New Look at Calculating Calcium Requirements, in metric units

OceanWe have worked with PACE Turf to develop the Minimum Levels for Sustainable Nutrition (MLSN). These new guidelines ensure ample amounts of mineral elements are present in the soil to meet the requirements of turfgrass. The target for calcium is 360 ppm using the Mehlich 3 extractant, meaning that if calcium is present in the soil at 360 ppm or more, none is needed as fertilizer, because the soil can supply all the calcium that the plant requires. 

Calcium is also used to replace sodium in the soil. For that use of calcium, it is not a fertilizer, but rather a soil amendment. And the MLSN guideline for sodium is to have no more than 110 ppm in the soil, measured in a Mehlich 3 extract.

SalinityWhat if you have sodium at more than 110 ppm in the soil, perhaps from salt spray, or more likely, from sodium in the irrigation water? A new document from PACE Turf explains how to calculate the calcium requirement. That document, however, uses pounds and acres and thousands of square feet. I make the calculations here in metric units.

  1. First we look at how much sodium is in the soil. Our goal in this calculation is to find out how much calcium we need to apply to match the amount of excess sodium. If we can apply calcium to match the sodium, then it will be easier to leach the sodium from the soil.
  2. Let's pretend we have just received a soil test report and the sodium is at 150 ppm. This means that there are 150 mg of sodium for each kg of soil, and our excess sodium is 40 ppm (or 40 mg) more than the 110 ppm maximum on the MLSN guidelines. 150-110 = 40 mg/kg
  3. We can take that 40 mg of sodium and find out how many ions it is. One millimole of sodium has a mass of 23 mg, so we have 40/23 = 1.7 millimoles of sodium per kg. Let's write millimole as mmol for simplicity. Now we are ready to calculate how much calcium we require.
  4. Sodium is a monavalent cation, meaning it has one positive charge for each ion. We have 1.7 mmol of sodium, and also 1.7 mmol of positive charge. We need 1.7 mmol of positive charge from calcium. But calcium is a divalent cation, with two positive charges for each ion. So we only need 0.85 mmol of calcium. One mmol of calcium has a mass of 40.1 mg, so we need 40.1*0.85 = 34 mg of calcium. We've almost got it: 34 mg of calcium will provide the same amount of charge as will 40 mg of sodium.
  5. We now need to consider how much area and volume of soil we will apply that calcium to, so that we can get an application rate. Let's assume we have a rootzone 15 cm deep and with a bulk density of 1.33 g/cm3. In that case, 1 m2 of the soil has a mass of 200 kg. Remember, we've previously been making our calculations on a per kg basis. Now we want to change to square meters. To replace the excess sodium, we have already calculated that we need 34 mg of calcium per kg of soil. And we have 200 kg soil in 1 m2, so we need 34*200 = 6,800 mg calcium per square meter (6.8 g/m2).
  6. That's how much calcium we require in this example. If you want to simplify this and not work through the calculation every time, we can simply apply 0.17 mg of Ca for every 1 ppm sodium in excess of 110 ppm. If sodium were at 120 ppm on the soil test, the calcium requirement would be (120-110)*0.17 = 1.7 g/m2. If sodium were at 204 on the soil test, the calcium requirement would be (204-110)*0.17 = 16 g/m2

Of course, if you have more than 360 ppm Ca and less than 110 ppm Na on the soil test, then there is no calcium requirement. The soil already has enough, and the sodium does not require treatment.

World Cities Plotted by Climatological Normals, April


This chart shows 46 world cities plotted by their average temperature, precipitation, and sunshine hours during April.

Normal temperatures this month at Hong Kong, Hilo, Honolulu, Miami, and Rio de Janeiro are all very similar, ranging from 22.5°C at Hong Kong to 24.5°C at Rio de Janeiro, yet there are major differences in sunshine hours, with a range from 102 at Hong Kong to 294 at Miami. These differences in sunshine hours translate into differences in photosynthetically active radiation, producing completely different growing environments for grass, despite the similar temperatures that are suitable for the growth of warm-season grasses.

This difference is exemplified by Honolulu and Hilo. These cities are only 340 km apart, but when looking at the climate, we see that Hilo has more in common with Hong Kong and Rio de Janeiro than it does with Honolulu. I visited Hilo and Honolulu last month and experienced this difference in climate. These pictures show what the climate chart predicts.