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March 2016

That's not the way it is supposed to work

Of the many interesting things in the report by Gelernter et al. on the GCSAA's second nutrient use survey, I was especially intrigued by the part about soil testing.

First, a little background. If one has no idea how much of any mineral element is in the soil, then the logical amount to apply as fertilizer is just a little bit more than the grass can use. This guarantees that the grass will be supplied with all of each element that it can use. That's like an estimate of the maximum amount of fertilizer to apply.

Why soil test? Because soil testing allows for more efficient application of fertilizer. After finding out how much is in the soil, one can often reduce the quantity of fertilizer applied, because one knows that the soil can supply some portion of the plant's requirements.

With no soil testing, it makes sense to apply all that the grass could use. With soil testing, it makes sense to apply only the amount that the grass could use that can't be supplied by the soil. It's evident that the maximum amount of fertilizer should be applied when one doesn't know the nutrient content of the soil, and that in the most infertile soils, the quantity of nutrients required as fertilizer will be close to the maximum, with the quanity required as fertilizer decreasing as soon as the soils have some quantity of nutrients.

In the last chapter of A Short Grammar of Greenkeeping, I wrote that "I'd recommend soil testing, because in most soils the correct interpretation of soil tests can reduce the quantity of fertilizer that is applied."

You may have heard me say that soil testing is broken. For more background:

Now back to the GCSAA nutrient use survey results. Here's what the survey says:

"Despite the fact that respondents said that they used soil tests to reduce reliance on fertilizers, higher use rates were observed for respondents who conducted soil tests (Table 7). This apparent contradiction may be due to some of the turf fertility guidelines currently in use, which target higher nutrient levels than are required for acceptable turf growth ...

As a result, those who conduct soil tests with the belief that it will help them to reduce fertilizer inputs may end up unintentionally increasing fertilizer instead, likely because the guidelines used to evaluate their results may be higher than necessary."

That's not the way it is supposed to work. For more, check out the fertilizer and soil categories on the blog.

Every spring when the snow melts ...

I look forward to some photos from Doug Soldat. For the past three years, he's had some fascinating photos to share of snow mold on creeping bentgrass. And each year, there was more snow mold where potassium fertilizer was applied, and less snow mold where potassium wasn't applied.

Spring of 2014

In the spring of 2014, there was more snow mold where K was applied.

Spring of 2015

Last year, there was also more snow mold where K was applied.

Spring of 2016

This year, it happened again. There was more snow mold where K was applied.

Doug will be talking about K in a TurfNet webinar in April: Is Your Potassium Program Hurting or Helping Your Turf?

On those creeping bentgrass plots in Wisconsin, adding K increases snow mold. No K had less snow mold.

At Rutgers, annual bluegrass plots deficient in K have had more anthracnose in summer and more winter injury. Eliminating the deficiency reduced those problems.

Then there is the MLSN guideline for K of 37 ppm. I recommend keeping the soil K above 37 ppm (Mehlich 3 extractant).

And there are hundreds of other studies about K. Some show a benefit from adding K, and some don't. I haven't read all of them, but I have read a lot of them. This sounds like it could be pretty complicated.

Actually, I don't think it is. Here's what seems to be the case, for both warm-season and cool-season grasses:

Ensuring the grass is supplied with all the K it can use will provide all the benefits associated with K. Adding more than that usually has no effect, other than wasting time and money, but sometimes has a negative effect.

As a turfgrass manager, all one has to do is ensure the grass is supplied with all the K it can use. This can be accomplished in 2 ways. One is by keeping the soil K above the MLSN guideline. A second is by applying N:K in a 2:1 ratio for cool-season grasses, a 1:1 ratio for seashore paspalum, and a 3:2 ratio for other warm-season grasses. I wrote about that in the final chapter of A Short Grammar of Greenkeeping and in The (New) Fundamentals of Turfgrass Nutrition.

Note that I do not recommend tissue testing for K (or any other element).

If you want to read more about K specifically, and about how the benefits of K come from correcting a deficiency, I recommend:

Optimum playing conditions, minimum inputs

"Mekong River diverted into Thailand's waterways, worrying drought-stricken neighbours like Vietnam," says a recent headline. "Drought exacts toll on crops in region," says another. And "China has embarked on an unprecedented 'water diplomacy' mission to alleviate the drought in Laos, Myanmar, Thailand, Cambodia, and Vietnam by discharging massive quantities of fresh water downstream from one of its dams," says a third article.


The recent R&A Seminars on Sustainable Golf Course Design, Renovation and Maintenance in Asia, held in early March in Beijing and then in mid-March near Bangkok, were timely in addressing the use of water (and other resources) on golf courses.

Selection_037At these seminars, I spoke about how one can optimize the playing conditions of the golf course while minimizing inputs of resources such as water.

This 12 page handout has details of what I discussed, and includes links to articles and all my presentations.

One of the easiest ways to reduce the amount of water required is to minimize the area of maintained turf.

Another way to reduce the water requirement is to use drought tolerant species. In particular, one can produce the best surfaces with the fewest inputs by using native species.

I also explained how to calculate the irrigation water requirement for any area of turf. First, estimate the water use by evapotranspiration, then subtract the quantity of effective rainfall and adjust for the surface area to be irrigated. Then, make further adjustments for the distribution uniformity of the irrigation system and the salinity of the water, and one is left with the quantity of water required as irrigation.

It is quite useful to have this number, and especially to make that calculation for a drought year. In that way, the necessary amount of water storage can be built, or one can adjust the turfgrass area or turfgrass species to make sure the golf course will be sustainable in terms of water.


If there isn't enough water for irrigation, then some grasses will die. Seashore paspalum is the grass that requires the most water to survive in Southeast Asia, and it dies when irrigation water is not supplied. Calculating the irrigation water requirement and planning to have that much water available can be quite useful. As this article states, regarding the current drought, and planning for water availability in such conditions:

Such long-term planning is unfortunately uncommon, say agriculture experts. Dr Leocadio Sebastian, a Vietnam-based regional programme leader for the Consultative Group On International Agricultural Research, says governments tend to be reactive. "They tend to favour relief intervention."

For golf course turf, one can't expect relief intervention, so it is better to plan ahead by choosing grasses that require fewer inputs.

Hanging around 1750 all summer

I looked at the photosynthetically active radiation (PAR) in Corvallis and Ithaca for each day of 2015, and there was something strange in the data. I didn't think anyone would notice, but someone caught it right away:

The station -- I've used data from the U.S. Climate Reference Network -- latitudes at Corvallis (44.4°N) and Ithaca (42.4°N) are similar, so I expect the maximum radiation to be similar. In fact, on average during summer I'd expect Corvallis to receive more radiation, and Ithaca less, because of the climate differences between those two locations.

What's going on? Are my calculations wrong? Is it sensor error? Were there forest fires producing smoke over Corvallis through the summer of 2015? Was it exceptionally sunny in Ithaca, and cloudy in Corvallis? I decided to look at more years, getting data from every year since 2007 for comparison. I looked at the daily totals.


Something strange happened with the data for Corvallis in 2015. In all the previous years, there were some days with global solar radiation above 27 megajoules per square meter per day (27 MJ m-2 d-1). In 2015, nothing. At first I'd thought that the Ithaca data were abnormally high. But in looking at the data from 2007 to 2015, it seems that Ithaca is within a normal range of global solar radiation, but Corvallis data are abnormally low.

I counted the days with global solar radiation greater than or equal to 27 MJ m-2.


In the 8 years prior to 2015, Corvallis had 4 years with more than 40 days above 27 MJ m-2, and only 1 year (2011) with less than 20 days reaching that level. Then in 2015, 0 days.

I'm guessing this was an undetected sensor problem or other data error. The photosynthetic photon flux density (PPFD) in Corvallis probably should not be hanging around 1750 all summer. It was in 2015, because of the data I was working with. But after a closer look, those data seem abnormally low. I'd expect the PPFD in Corvallis to be blasting through to 2000 in early summer. Can anyone with a quantum meter in the Willamette Valley confirm this?

A rule of thumb for cloud effect on PAR

I've shared some charts of photosynthetically active radiation (PAR) as it changes through the day and through the year at different locations. For example, this is the PAR at Corvallis for each day of 2015.

image from

For each day, as a function of latitude, and for each time within the day, as a function of both latitude and longitude, there is a maximum possible quantity of PAR. Then, in areas with no tree or structural shade, the PAR will be close to the maximum possible quantity, unless there are clouds.

But how much do the clouds reduce PAR? If you carry a PPFD meter around with you all the time, you can check it yourself. If you don't carry a PPFD meter, I suggest this rule of thumb to get some idea of just how much the clouds are reducing PAR.


I explained this at the Asian Turfgrass Field Day last week, when it was conveniently partly cloudy, with clouds of varying thickness, and I also conveniently had a meter for measuring the PPFD.

If you don't have a meter, but pay attention to your shadow, clouds, and the sun location, you can get a pretty accurate estimate of PPFD. Here's the rule of thumb, for four possible levels of cloud shade:

  1. If there are no clouds, or there are no clouds between you and the sun, then you can expect the cloud shade to be negligible, and the PAR should be close to the maximum possible. This app calculates the maximum possible for any location.
  2. If you can see your shadow, but there are clouds between you and the sun, then expect the PAR to be reduced by about 25%.
  3. If the clouds block so much light that you cannot see your shadow, but you can still tell which part of the sky the sun is in, expect the PAR to be reduced by about 50%.
  4. If you cannot see your shadow, and at the same time the clouds are so thick that you cannot tell where the sun is in the sky, then expect the PAR to be reduced by about 75%.

When there are no clouds, then one will see the maximum possible PAR, as shown in this chart for Bangkok and Tokyo. They are different because Bangkok is about 13 degrees north of the equator, and Tokyo is 35 degrees north.

image from c2.staticflickr.comOne can also look at measurements of solar radiation and express them in units of PAR. Now the cloud effects are taken into account. For example, this is Ithaca, NY, and you can see the effect of clouds on PAR.

image from
PAR data for Corvallis and Ithaca are converted from the global solar radiation measurement of the U.S. Climate Reference Network sub-hourly data. I usually use a transmittance value of 0.75 on a clear day to estimate the portion of extraterrestrial solar radiation (Ra) that reaches the surface as global solar radiation (Rs). That's the basis for the max possible (blue lines) I've shown on these charts. But these ones use different transmittance values. I used 0.68 for Corvallis, and 0.8 for Ithaca, because those are what made a good match for the USCRN data for those locations. I'm not sure why the measurements are different on clear days -- Ithaca has a higher Rs than does Corvallis but only a small difference in latitude. That's something I'll study some more.

Delegate maps, presentations, and photos from Sustainable Turfgrass Management in Asia 2016

It was another fun conference in Thailand, as the TGCSA welcomed 283 delegates from 24 countries to Pattaya for the Sustainable Turfgrass Management in Asia 2016 conference. This conference is organized by the TGCSA and ATC for the TGA, with support from the R&A.

Thailand sent the most delegates, with 153; next was Vietnam, with 23, and then Singapore with 18. These maps show the delegate counts by country.

Data: forPlot • Chart ID: GeoMapID4c09296ac8a7googleVis-0.5.10
R version 3.2.4 (2016-03-10) • Google Terms of UseDocumentation and Data Policy

Data: forPlot • Chart ID: GeoMapID4c096e53e2b9googleVis-0.5.10
R version 3.2.4 (2016-03-10) • Google Terms of UseDocumentation and Data Policy

Presentation slides from this year's conference (and previous years) are available for download.

Boy Yothin took hundreds of photos from the conference, field day, and AGIF turfgrass management exhibition and made them available in this Facebook album. A few of his photos from the conference are shown below.







Monthly Turfgrass Roundup: February 2016

Here's a roundup of turfgrass articles and links from the past month:

Is the leaking barrel analogy irrelevant?

Andrew Anderson with sunrise and sunset photos in Sydney.

Comments about tournament conditioning guidelines.

Paul Robertson shared what he heard about MLSN at a seminar.

December and January daily light integral in Everglades City, Florida.

It's not really about extractable or available.

Alternative classifications for soil K.

Soil pH and the MLSN guidelines, is adjustment warranted?

Grant Saunders suggests growing less thatch.

Burning grass in the spring.

An ethical and common-sense approach to purchasing new products.

I don't recommend this article.

Al Bancroft shared this photo of Poa annua germination and presence affected by mowing height.

An evapotranspiration calculator.

For more about turfgrass management, browse articles available for download on the ATC Turfgrass Information page, subscribe to this blog by e-mail or with an RSS reader - I use Feedly, or follow asianturfgrass on Twitter. Link and article roundups from previous months are here.

Animated charts showing photosynthetically active radiation for a year

I spoke at the Sustainable Turfgrass Management in Asia 2016 conference about light at different locations. The presentations slides can be viewed here, or embedded below. For more about the conference, which saw 278 delegates from 24 countries and 5 continents travel to Pattaya this year, see this post at the Asian Turf Seminar site.

Light is important. Without enough light, grass won't grow well. I suggested that "no-problem" daily light integral (DLI) values for putting greens of bermudagrass, seashore paspalum, and zoysiagrass, may be about 40, 30, and 20 respectively. And I showed what PAR is, and how PAR is measured in one second as the photosynthetic photon flux density (PPFD), and then how all the PPFD over the course of a day are added together to make up the DLI.

I showed charts for one day, and also animated charts that show PPFD and DLI for every day of the year. This chart shows the maximum expected PPFD by time of day, and maximum possible DLI by day of the year, at Tokyo and Bangkok if there were no clouds. You may need to click the browser's "refresh" button to play these animations.


I wanted to visualize how these maximum possible values, on days when the sky is clear and about 75% of the extraterrestrial radiation reaches the earth's surface. To do that, I looked up the global solar radiation for Tokyo for every hour of 2015, converted those values to PAR units, and plotted them together with the maximum possible values assuming 75% transmittance of extraterrestrial radiation. That is plotted here.


I also explained that the global solar radiation has a large influence on the evapotranspiration (ET). I demonstrated this ET calculator that uses the Hargreaves equation to estimate the ET based on global solar radiation.