## A hypothesis about the most sustainable grass

##### 26 July 2016

I've written about zoysia growing faster than bermuda. Mike Richardson asked "is that better? Slow growing has always been one of my favorite traits of zoysia."

I answered that it is better, and that I would explain my hypothesis later. Here it is:

The most sustainable grass for a given location is the one that has the most growth per unit of N and per unit of H2O applied.

Definitions:

• most sustainable grass is the one that requires the fewest inputs to produce the desired surface

Assumptions:

• one considers all the grasses that could possibly produce the desired surface at that location
• from those, one selects those that don't die when N and H2O are reduced

It follows that of the remaining grasses -- those that don't die -- the one with the fastest growth rate will require the fewest inputs to produce the desired surface, because one can supply low amounts of N and water to that grass. The one with the fastest growth rate also gives the most maintenance options, because one can adjust the growth rate across a wider range.

## New paper on variability of hybrid bermudagrass used on putting greens

##### 25 July 2016

If you work with warm-season grasses, you will want to have a look at this new paper by Reasor et al. on the variability of hybrid bermudagrasses used on putting greens.

Ever see anything like this? Off-types growing in a green? Wondered if the off-types are contamination by a completely different grass, or if the grass has mutated?

This paper explains what can happen, what has happened, and why. Plus it has a historical review of these hybrid bermudagrasses used on greens. Find out where they came from and how the grasses are related.

Sometimes I write about papers that are behind a paywall and most people can't read (or at least don't want to pay the high fees to purchase). I'm glad there won't be that problem with this article, as Reasor et al. have published this open access so everyone can read it.

I've just spent a couple weeks with the lead author Eric Reasor (pictured at right in Japan) collecting data from bermudagrass putting greens in Asia.

He's been doing a lot of interesting research about ultradwarf bermudagrass, off-types within those grasses, and the management of putting greens to minimize problems with off-types. Watch out for more interesting research from him on this topic.

## Two fine articles about two important topics

##### 24 July 2016

When I visit Japan, I like to try the various flavors of soft ice cream as I go to different places. This is peanut soft cream in Chiba prefecture.

Another thing I like to do is browse the magazines to find interesting articles. I had a chance to see recent issues of Monthly Golf Management this week, and I was pleased to see two articles that I recommend in English are now available in Japanese.

If you are in Japan, read them in the magazines. For the original versions, if you haven't read them yet:

How to develop a water budget for your golf course: "How much water does your golf facility need each year to keep the turf healthy?"

Turfgrass fertilization: "supplemental nutrition is typically necessary to strengthen critical plant components so turf can provide desirable playing surfaces ... This article covers several aspects of turfgrass nutrition, such as determining how much fertilizer is actually needed, fertilizing for enhanced playability, the economics of turfgrass fertilization, and dispelling some of the myths surrounding fertilizer applications."

## Soil temperature and fairway management from 1980

##### 08 July 2016

I don't recall what I was searching for, but I stumbled fortuitously across this article by Oscar Miles from the Green Section Record in 1980:

Soil temperature and related fairway management practices -- northern turfgrasses

It's a great read, and quite interesting to see how he anticipated so much of the maintenance as conducted today.

"The additional data, I believe, will help us set up a program that a data processor or computer can maintain for us. I feel it is inevitable that mini-computers will make their way into golf course management systems. This is not as far-fetched as you might think."

p.s. Now I recall. I probably was searching for something related to soil water content and nighttime soil temperatures in summer.

## Turfgrass and shade: daily light integral (DLI) in Sydney

##### 07 July 2016

The Australian Government Bureau of Meteorology (BOM) provide satellite-derived global solar radiation data. I downloaded 2015 and 2016 data for station number 66120 (Gordon Golf Club). The data are in energy units of megajoules per square meter per day. I multiplied by 2.04 to convert to daily light integral (DLI) units of moles per square meter per day.

This is the DLI in full sun, adjusted for clouds. Any tree or structural shade will result in a lower DLI.

Looking at monthly summaries of DLI, one can see the median and the normal range in each month since January 2015.

I downloaded temperature data from the Sydney Airport (SYD) and used those to calculate an estimated DLI using the Hargreaves equation, as described in Estimating daily light integral in 4 Tennessee cities. I did not make any corrections to the estimate from the Hargreaves equation, and SYD is about 25 km south of Gordon. Still, the uncorrected Hargreaves equation gives a decent estimate of DLI.

## Monthly Turfgrass Roundup: June 2016

##### 07 July 2016

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

Kreuser with a cool video of syringing to cool turf:

Silvertown on Agatha Christie and Park Grass.

MLSN data and code.

The preprint about the MLSN guidelines was published.

Sand as a finite resource in the NY Times.

TPC Piper Glen with decades of aerification holes:

99 articles titles from Golf Course Seminar (Japan).

Robertson showed how to double cut and triple roll:

Does soil water content affect nightime soil temperatures in summer?

Six Shiny apps for making turfgrass calculations.

Daily light integrals (DLI) for warm-season putting green grow-in.

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.

## This is what the southwest monsoon looks like

##### 06 July 2016

I downloaded daily precipitation data for Mumbai from Weather Underground. That's what the start of the monsoon season looks like. Almost no rain for the first half of the year, and then the monsoon.

The India Meteorological Department (IMD) have a great web page all about the monsoon. This chart pasted below shows the advance of the monsoon over the past few weeks.

## Checking my calculations

##### 28 June 2016

I enjoyed reading the recent paper by Hodges et al. on Quantifying a daily light integral (DLI) for establishment of warm-season cultivars on putting greens. They measured the DLI at Starkville for the duration of this experiment, from 13 June to 29 September 2013 and again from 2 June to 27 September 2014. The mean DLI in full sun, on their test area, was 42.3 mol m-2 d-1 when averaged across those dates.

Last year I made some calculations to estimate DLI. You can read about that in Estimating daily light integral in 4 Tennessee cities. I wondered what that calculation method would give for a mean estimated DLI in Starkville. That is, Hodges et al. measured DLI with a quantum light sensor from Spectrum Technologies, and I wanted to check my calculations to see how close the estimated DLI was to the measurement.

The code for the calculations is in the dli_tn repository.

In full sun, Hodges et al. measured an average DLI of 42.3. The mean estimated DLI, using my calculations, for those same dates, was 40.6. Not too far off. To put the error of my estimate into context, that's a difference of 1.7 moles. An hour of midsummer midday sun at that location will have about 7.2 moles of PAR per hour, so 1.7 moles is equivalent to about 15 minutes of midsummer midday sun.

## Six turfgrass Shiny apps

##### 27 June 2016

These Shiny applications make calculations related to turfgrass management.

### Evapotranspiration (ET) calculator

Returns the reference and crop evapotranspiration for a day given inputs of latitude, maximum and minimum air temperatures, and crop coefficient. Based on the Hargreaves equation.

### Sustainability index

Returns the sustainability index (SI) based on soil test inputs. This is a direct comparison of input soil test results to the MLSN data.

### PPFD by time, date, and location

Returns the expected photosynthetic photon flux density (PPFD) for a second within any specified minute, given inputs of latitude, longitude, date, and time. Also returns expected daily light integral (DLI) at that location if it is sunny all day.

### MLSN K fertilizer calculator

Calculates the fertilizer K requirement given inputs of grass species, soil test K, and annual N rate.

### ET（蒸発散値: 標準 ETと特定作物 ET）計算機

このプログラムは、標準蒸発散値(ETo) を、年月日、緯度、その日の最高気温と最低気温を基にしてmm 単位で計算します。算出された ETo に、作物係数を乗算すると、 その作物の蒸発散値（ETc）が求められます。これらの計算はHargreaves の ETo

### MLSN ガイドラインからK要求量を求める

ここでの計算は、持続可能な最低栄養 （MLSNガイドライン） をベースとしています。

## Does soil water content affect nighttime soil temperatures in summer?

##### 26 June 2016

I was wondering what the effect was. I expected a 1 or 2°C decrease in nighttime soil temperature in drier soils, compared to soils with more water. I didn't find it.