## Daily versus monthly calculations of ET and irrigation requirement

##### 29 October 2016

I showed how weather data can be used to calculate a daily soil water balance. One can adjust the rootzone characteristics, and the timing and amount of irrigation, so that the calculations are representative of what one wants to know.

By keeping track of what the soil water content would be on each day, given the actual weather conditions, and given the water holding capacity of the specified rootzone, one can find how much irrigation water would be required.

I've also made calculations using the standard method, which takes the evapotranspiration (ET) and subtracts the effective rainfall. I've used this method before to make calculations, and it made sense to me, but I've realized that this method doesn't account for rootzone depth. For turfgrass, one should probably adjust the effective rainfall calculation for each site based on the rootzone depth.

I wondered if these methods give a similar result in predicting the irrigation requirement. I had daily data from Sapporo from 2013 to 2015, and I also got the monthly averages or totals for the same time period. I've just made some calculations to find out.

I looked at the months from April to October in each year. That's a total of 21 months.

For the ET, the result is almost the same whether it is calculated daily, and summed for a month, or whether one calculates ET using the monthly data.

For the irrigation requirement, there is not a consistent agreement. I made these calculations based on an approximation of a loam soil with a 10 cm rootzone depth, a field capacity of 40% (by volume), with irrigation supplied to return the soil to field capacity when soil water content would drop below 20%.

I've got some more calculations to make about this. The standard method seemed pretty good to me until I started making the daily calculations.

## The daily soil water balance at Sapporo from 2013 to 2016

##### 27 October 2016

One can calculate a water budget for a particular location to get an estimate of how much irrigation water is required. This article from the Green Section Record describes those calculations.

If one considers the depth of the rootzone, and then steps day by day through the year, the irrigation water requirement can be calculated as part of the daily soil water balance.

I downloaded data for Sapporo for the past few years. Since the ground is covered in snow during the winter, I'll just show the daily water balance from 1 April to 31 October. This is for a simulated 10 cm rootzone with a field capacity of 23% and irrigation applied to keep the soil from dropping below 10%. That will be something like a golf course putting green. The blue line shows the soil water content. The black circles show the irrigation events. Interesting stuff.

## Top 25 tweets of the Ryder Cup*

##### 12 October 2016

There's an asterisk on this, because I limit this to 4,098 unique tweets returned by a search for ct_turf from September 22 to October 4. From those, I selected the 25 with the highest favorite count. Note that the favorite count was at the time of the search, which was multiple times from Sep 29 to Oct 4. Thus, the favorites on the tweets may be quite different now from the time of the search.

As an example, Jeff Johnson's "tweet of the year" about amazing surfaces didn't make my top 25 because that tweet was saved just a couple hours after it had been posted, when it hadn't yet reached the 103 favorites that I see at the time of this writing.

From the 4,098 tweets returned by a search for ct_turf, I wanted to find those that had the most favorites. That's an easy assessment of which tweets were the most popular.

First, I checked the favorite count on all the tweets. I had a set of tweets from the evening of September 22 until midday on October 4.

Then I found the top 25 in terms of how many favorites they had at the time the search was made.

For easy viewing, I put all 25 of those tweets together here:

## Monthly Turfgrass Roundup: September 2016

##### 11 October 2016

In this month’s roundup: fertilizer, roots, golf in Japan, identifying a turf disease, the Ryder Cup, putting green performance, and much more.

What's the probability of a positive response to fertilizer application?

Sue Crawford reports on a #MLSN trial green:

Golf with two greens on each hole.

Lawn fertilizer calculator from University of Missouri.

Eric Reasor shared this tip on scouting for offtype grasses:

Fast release fertilizer, burn, and root growth.

Andrew McDaniel shared photos of pre-Ryder Cup preparations:

Measuring ball roll dispersion on putting greens.

Andrew Kniss on the environmental impact quotient (EIQ). It's not better than nothing.

Paul Jansen on the Japanese golf experience.

A new Shiny app with the temperature and sunshine combination for 11 cities in Japan.

Chris Tritabaugh from the 1st tee at Hazeltine:

The turfgrass disease called dog's footprint.

Documenting more preparations for the Ryder Cup:

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.

## Applying the grammar of greenkeeping

##### 10 October 2016

Over the past two weeks, I've had multiple conversations about the way I think of turfgrass management. It all starts with a definition of greenkeeping as managing the growth rate of the grass. I wrote about this in A Short Grammar of Greenkeeping. You can get your copy here.

Application of the grammar allows for easy communication among turfgrass managers about the work they are doing. I'll use the creeping bentgrass greens at Hazeltine National GC as an example. Volunteers from near and far were at Hazeltine during the Ryder Cup.

Let's say that I was from Madrid, or San Francisco, or Sydney, and I wanted to get green conditions that were more like those at Hazeltine. One of the ways I would try to do that would be to apply a similar quantity of nitrogen. But how to compare locations?

I would use the temperature-based growth potential (GP). For Minneapolis, the GP looks like this.

If I set the maximum monthly N at 3 g/m2, and multiply by the GP, I get a maximum annual N of 13.3 g/m2 for that location (Minneapolis). Now I'll make up a number, because I don't know exactly what it is, but let's say the actual quantity of N applied at Hazeltine was 9 g/m2.

I'll use the log percentage (L%) difference for consistency. The L% is the natural logarithm of the ratio of two numbers, multiplied by 100:

$L{\%}&space;=&space;100\:log_{e}(\frac{y}{x})$

If 9 g N were applied at Hazeltine, and the value calculated using GP as described above is 13.3 g, that is a 39 L% reduction.

If I want to apply proportionally the same amount of N at another location, I can calculate the GP amount, which I'll call a standard value, and then take a 39 L% reduction.

The standard using these calculations comes to 16.7 g at Madrid, 20.1 at San Francisco, and 28.9 at Sydney. Knowing that there was a 39 L% reduction at Hazeltine, my starting point for Madrid, after applying the same reduction, would be 11.3 g N/m2. At San Francisco, the N would go from the standard calculation of 20.1 down to 13.6 g, and at Sydney the 39 L% reduction takes N from 28.9 to 19.6.

This grammar facilitates the rapid sharing of relative inputs used to produce turf surfaces all over the world. Let's say we know there are amazing bentgrass greens in Sydney with N inputs of 10 g/m2/year. A corresponding quantity of N in Minneapolis would be 4.6 g.

This same approach can be applied for the quantity of water supplied in comparison to evapotranspiration (ET), to frequency of mowing, to evaluation of the growth rate, to assessment of the photosynthetic light, and so on. I find this approach quite useful in rapid implementation of maintenance practices that work well at location A, applied to location B. One then has a site specific starting point that can be further adjusted at location B, based on turfgrass response at that location.

## Golf and health

Yesterday I saw the new paper by Murray et al. in the British Journal of Sports Medicine on The relationships between golf and health: a scoping review. The reviewers identified 301 studies on this topic that met their search criteria, and then they summarized the results in terms of:

• participation
• golf and physical activity
• golf and longevity
• golf and physical health
• cardiovascular system
• respiratory system
• metabolic health
• cancer risk
• musculoskeletal health
• golf and injury
• golf and mental health/wellness
• mental health
• mental wellness

It's a comprehensive review, and if you are interested in this topic, I suggest you read the paper. From the golf and physical activity section, here's the calorie burn and walking distance:

Studies assessing calorie expenditure during golf typically classify golf as a moderate intensity physical activity with energy expenditure of 3.3—8.15 kcal/min, 264—450 kcal/hour, and a total energy expenditure of 531—2467 kcal/18 holes. Golfers walking 18 holes take between 11,245 and 16,667 steps, walking 4—8 miles, while those playing and riding a golf cart accrue 6280 steps or just under 4 miles.

This ties in well with something I've written about before, which is golf and health and multifunctional facilities. In the words of Don Mahaffey, "golf is good for you" but this aspect of golf is often overlooked.

See these posts for more from Don Mahaffey, and from info about STERF's research into multifunctional golf facilities:

## A few examples of multifunctional facilities

Weddings and banquets, of course, are common at many facilities. This is a chapel at Club de Golf Escorpión in Valencia.

Use of a practice tee for sports training, at Escorpión.

A football field at El Saler, just to the right of the 8th and 9th holes. This has been used by the Spanish national team and by Valencia CF, among many others.

Birdwatching is a common activity at El Saler, and this sign near the clubhouse shows many of the species one can find in this area.

Many golf facilities have trees or hedges with fruits or nuts. At Golf Costa Brava, the cork oaks are harvested.

Walking, hiking, or biking the Cami Ral will take one right through PGA Catalunya.

Hiking paths at Domaine de Falgos in the Pyrénées start at the golf clubhouse.

The driving range fairway at Domaine de Falgos doubles as a rugby field.

## A Ryder Cup miscellany, in charts

##### 06 October 2016

I was recently at Hazeltine National Golf Club for the Ryder Cup. When I arrived, I was informed that it had been extraordinarily rainy since early to mid-August. I had a chance to observe the rain myself as well. I wondered just how extraordinary the rain was, so I looked it up.

You can see all the charts I made in this Flickr album.

Another thing I looked at was when, who, and about what were people communicating with Chris Tritabaugh, the golf course superintendent at Hazeltine National Golf Club.

These are the words used most often during the week in tweets mentioning Chris's Twitter account.

This shows the discussion about the @ct_turf account on Twitter for the week. There are a number of hubs in the discussion.

Zooming in to just one hour on Saturday morning, one can see accounts grouped into conversations based on who was communicating at that time.

I even made a word cloud, these for the conversation on Saturday, 1 October.

All 33 charts are in this album if you would like to see more.