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.
In 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.
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.
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.
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.
@asianturfgrass looks like whatever it caused the damage was applied by back pack sprayer. Not to familiar with warm season issues...
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.
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.
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.
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).
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.