"I've waited far too long to voice my opinions concerning this extraordinary profession of greenkeeping"

How's that for a start? "The Walking Greenkeeper" introduced himself this morning. I expect this will be a fun blog to read.

Selection_010Now for an assortment of things that came to mind today, all of which are in some way related to Joe's blog post.

He wrote about some of his research this winter. Among other things, he mentioned me, MLSN, Jason Haines, and Chris Tritabaugh. "These fellas," he wrote, "and what I consider to be their alternative style to greenkeeping have inspired me ..." -- that's awesome.

So what came to mind? First, the #MLSN approach is about something very specific -- making fertilizer recommendations from soil tests to prevent nutrient deficiencies by ensuring the grass is supplied with enough of each element. However, the approach we have taken with MLSN has attracted interest from turf managers around the world who are interested in minimizing other inputs as well. And it is a lot of interest. I've been surprised that the MLSN newsletter mailing list, started just 6 weeks ago, already has more than 300 subscribers, from more than 30 countries.

If you are interested in the MLSN approach, you can subscribe to the newsletter here.

If you want more than just MLSN, you can sign up to the ATC newsletter here.

Here's an interesting question. Just what is the MLSN approach? Nadeem Zreikat wrote that he prefers efficient to minimalist:

Here's how I'd describe it. Lots of people are interested in MLSN and in the idea of managing things as efficiently as possible. I'd describe what I try to do, and with MLSN as a part of that, in this way:

For turf management at any site, the first thing to do is to define the conditions that one is trying to produce. Then, produce those conditions with the fewest possible inputs.

One could describe that as efficiency, or as minimalistic. I think both words, and many other words too, can fit the MLSN approach.

I wrote more about that in the Short Grammar of Greenkeeping. To produce the desired conditions, the turf manager manipulates the growth rate. In the Short Grammar, I wrote that greenkeeping can then be defined as modifying the growth rate to get the desired surface conditions. And the grammar provides a framework for adjusting the inputs to produce the desired conditions.

If that all sounds really vague, you'll want to read a great description of that approach in practice. I recommend Jason Haines' Turfhacker summary of everything that's interesting to me as a description of how these principles can be applied.

The whole idea is to produce the conditions we want, doing so with the minimum amount of work. Maybe that's efficiency, or minimalism, or sustainability, or something else. But that's where I'm coming from, that's the type of definition that the MLSN approach fits into, and this is for any type of turf.

I made a huge omission in last month's roundup. I forgot to include the 2016 Ryder Cup: Hazeltine National Turfgrass Team video featuring Chris Tritabaugh.

2016 Ryder Cup: Hazeltine National Golf Club, The Turfgrass Team from Chris Tritabaugh on Vimeo.

This is part of the approach too, and the video shows it. Be passionate about the work. Produce the conditions one is trying to produce. Do so with a minimum of inputs. Or as efficiently as possible. Have fun doing it. Find ways to do it better.

I expect everyone in this business is doing that in some way. It seems to me that the MLSN and Short Grammar approaches have provided a framework from which we can all work on and compare ways to do it better.

A Shiny app with adjustable rootzone characteristics and irrigation rules

I made this Shiny app that calculates the daily soil water balance.

The idea of the app is to change the soil conditions, specifically the rootzone depth and the field capacity, to see how changes in those parameters influence the irrigation requirement.

And the irrigation "rules" can be changed too. When will irrigation water be added? How much water will be added? What is the crop coefficient? What is the distribution uniformity of the irrigation system?

Then the soil conditions and the specific irrigation "rules" are matched to a year of weather data from a location, to see how any changes influence the amount of water required to satisfy the rules.


A water budget that accounts for rootzone depth

There is an excellent article in the Green Section Record that explains how to estimate irrigation water requirements.

Based on this approach, where the grass uses a certain amount of water, and then one accounts for the effective precipitation, it seems like one has the answer to the irrigation requirement. If the grass needs the water, but the effective precipitation cannot supply that water, then that difference between the amount needed and the effective precipitation must be the irrigation requirement, right?

This approach works perfectly where it doesn't rain, because the amount the grass uses is the amount required as irrigation.

As I started making these calculations, I realized that it gets a bit trickier where it rains. The reason for that is the effective precipitation. How can one make an accurate assessment of that? And wouldn't it make sense to include something about the ability of the soil to store the precipitation?

Where it rains, one can consider both the depth (and the water holding capacity) of the rootzone, and also consider how much water is in the rootzone at each precipitation event, and thus how much water holding capacity the soil has for each rainfall.

I've found the daily soil water balance to be an easy way to make precise calculations. This approach was also used by Gelernter et al. in their analysis of water use on golf courses in the United States.

Here are some calculations for Khon Kaen, showing the different results obtained by calculation method, year, and changes in rootzone depths or irrigation rules.

For more about these calculations, see:

Turfgrass roundup: February 2017

From Jason Haines, can one introduce more sand with solid tine aeration?

He also shared his slides from GIS, including on how reduced fertilizer has benefited my golf course.

K fertilizer and snow mold photo from Doug Soldat:

The Micah no jikan book (芝草科学とグリーンキーピング (マイカの時間 The BOOK) is now available.

Burning noshiba for the shiba yaki ceremony.

The slides from the #MLSN and GP seminar at GIS.

More details: another year, and another set of photos from Doug Soldat showing K fertilizer and more snow mold.

Three salinity levels, how do they affect the grow-in?

Five grass varieties 28 days after planting.

I created and sent the first MLSN newsletter. Read it here, or subscribe to be sure to get the next one.

Ian Daniels shared some good advice:

Peter McCormick wrote another interesting article at TurfNet.

Are you subscribed to the ATC updates mailing list? Or the MLSN newsletter list? 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.

Estimating irrigation water requirement for different soil conditions

In previous posts, I wrote about the daily soil water balance and irrigation frequency using Bangkok (DMK) weather data, and showed how changes in irrigation "rules" can change a predicted irrigation water requirement, that time using Phuket (HKT) weather data.

Thailand conveniently has golf courses adjacent to many of its major airports, so I can imagine turf being maintained at that location, and then make the calculations using data from the airport.

Let's go to Chiang Mai. The Star Dome Golf Club sits right next to Chiang Mai International Airport (CNX).

Now I want to consider fairways, and specifically the soil type of the fairway. There are a number of advantages to growing fairways in soil, rather than in sand, and using surface and subsurface drainage, and perhaps a bit of sand topdressing, to create the desired playing surface. One of the advantages to growing in soil is a lower irrigation water requirement.

I'll use 2015 weather data from CNX. Let's imagine a fairway with a 20 cm rootzone depth, a field capacity of 40%, and irrigation at 20% to return the soil back to field capacity. With 2015 weather data, that gives an expected irrigation requirement of 718 mm.

That's a deep and infrequent irrigation regime, and with a 20 cm rootzone depth, about 40 mm will be required at each irrigation event. That's a lot of water. It would probably be more reasonable to do more frequent irrigation.

And that can save water too. For example, with that same rootzone depth and field capacity, but now irrigating at 24% to increase VWC to 30% (supplying about 12 mm at each irrigation event), the expected irrigation requirement goes down to 674 mm.

In SE Asia, it is common to sandcap fairways. For example, see this course now under construction in Thailand:

What would the irrigation requirement be for a sand rootzone at CNX in 2015? I'll keep the same rootzone depth and the same crop coefficient and distribution uniformity, just changing how much water is held in the rootzone because of the sand. I'll estimate that a fairway sand will have a field capacity of 20% (I think that is a generous estimate) and that irrigation will be supplied at a VWC of 10% to return the soil to field capacity. That gives an estimated irrigation requirement of 909 mm.

For simplicity, let's say that for the soil rootzone, the irrigation requirement is 700 mm, and for the sand rootzone it is 900 mm. Let's say this water requirement is for 10 ha of irrigated fairways. For the soil fairway condition, that gives an irrigation requirement of 70,000 m3. With a sandcapped fairway, an extra 20,000 m3 are required. Plus the energy to pump the extra water.

What happens to the irrigation water requirement after changing the irrigation "rules"?

I've shown how calculation of the daily soil water balance, matched to precipitation data, can be used to estimate the irrigation water requirement for a given set of irrigation "rules." That is, if I calculate how much water is in the soil (details about the calculation method here), carefully adding in the amount added by rainfall, and subtracting the amounts lost to drainage or evapotranspiration, I can determine when and how much irrigation is required.

And the irrigation rules are things like the quantity of water I will apply at each irrigation, the soil's field capacity, at what quantity of soil water will I reapply irrigation, the distribution uniformity of the irrigation system, and so on.

The first set of calculations I showed were for a location in Bangkok. Now let's go south, to the island of Phuket, and look at the irrigation water requirement using weather data from recent years. I got the data from the Phuket International Airport (HKT), which is just north of Blue Canyon Country Club. I'll imagine that these calculations are for a hypothetical stand of turfgrass at that location.

This is a view over the Canyon course looking north, with the control tower for HKT visible in the top left corner.


Now I will calculate the irrigation requirement using the weather data from HKT in 2015. First, I'll start with a scenario of:

  • rootzone depth at 10 cm
  • field capacity of 25% VWC
  • irrigation threshold of 12% VWC -- when the soil is predicted to drop below 12%, an irrigation event is triggered
  • each irrigation is set to return the soil to field capacity
  • the crop coefficient used to adjust the reference evapotranspiration to crop evapotranspiration is 0.7
  • the distribution uniformity of the irrigation system is 0.75

Calculating the water balance for every day of the year with those conditions, the annual irrigation water requirement is 644 mm.

That would be a classic deep and infrequent irrigation regime. For that same location and same weather data, what happens if I change to a light and frequent approach? Now I'll irrigate at 15%, rather than at 12%, but I will add only enough water at each irrigation to reach 20% VWC in the top 10 cm, rather than 25%. In this case, the annual irrigation requirement drops to 620 mm.

What might happen if I start using a (or use an improved) soil surfactant? I could reasonably expect that the spatial variability in soil water content would be reduced, and that the soil would be easier to rewet after drying. I can go back to the original deep and infrequent rules, but now with the surfactant use I will let the irrigation threshold drop down to 10%, instead of the more conservative 12%. With the surfactant, I think that is a reasonable and safe adjustment. Now what happens? The irrigation water requirement drops from 644 mm to 605 mm.

What happens if I can get the roots to grow a little deeper? If I then increase the rootzone depth from 10 cm to 12 cm, the irrigation water requirement goes from 620 mm down to 569 mm.

Here's a way to make a substantial drop in the irrigation water requirement -- improve the distribution uniformity of the irrigation system. If I improve the DU from 0.75 to 0.8, while keeping the other rules as in the previous scenario, the irrigation water requirement goes from 569 mm to 533 mm.

And if I then go back to frequent irrigation rules, in this case irrigating at 15% and adding water to increase the top 12 cm to 20%, the irrigation water requirement is 529 mm.

Simulating irrigation frequency at the world famous "snake" course

The "snake" course, and simulation using the daily soil water balance

Many of you will have seen the Kantarat Golf Course when flying into Bangkok. Maybe you've played it. It's a cool course, set between the two runways at Don Mueang International Airport in Bangkok.

It is commonly called the snake course, and I can confirm there are a lot of snakes out there.

image from c1.staticflickr.com

And then there are the planes, and the crossing of active taxiways.



The most common problem with irrigation water quality is high salinity, and the solution to that problem is adjusting the quantity of water supplied. At the end of yesterday's seminar, I switched from talking about water quality, and discussed the application of the daily soil water balance in managing irrigation water quantity.

I used the snake course as a hypothetical location, because I had a set of daily data from the weather station at Don Mueang (DMK).

More about irrigation frequency

I've written previously about whether it is better to do deep and infrequent irrigation, or whether it might actually be better to irrigate frequently in small amounts. I applied the daily soil water balance to work through this for a location at DMK.

Let's say we are growing grass at DMK and have a 10 cm rootzone depth and then the weather happens as it did every day at that location in 2015.

I'll have some plan of how I'm going to irrigate, too. Let's say there is a field capacity of 25%, and I expect the grass may wilt when the volumetric water content (VWC) is less than 10%. I will try to irrigate to keep the soil from dropping below 12%, and every time I irrigate, I will fill the soil back to field capacity. When I do that, with the details as shown here, for example using a crop coefficient (Kc) of 0.7 and a lower quartile distribution uniformity (DULQ) of 0.75, I can then simulate the soil water content day by day through the year. I do that by stepping through each day of the year, with the evapotranspiration and precipitation as it happened, adding irrigation as required by the rules I've set. Doing that for 2015, the irrigation requirement is 1011 mm and the median VWC through the year is 19.7%.

image from c1.staticflickr.com

I can also simulate the soil water content and irrigation required for a different set of rules, but for the same soil and weather. I did that, for those same 2015 weather data, now irrigating at 14% rather than at 12%, but instead of supplying enough water to raise the soil back to field capacity, I only add enough to increase the soil water to 18%. When I do this, the irrigation requirement drops to 970 mm, and the median VWC goes to 15.5%.

image from c1.staticflickr.com

I checked this for 2016 data, and the results were similar: a total 949 mm of irrigation required and median VWC for the year of 20.2% using deep and infrequent rules, 889 mm irrigation and a median VWC of 15.6% with light and frequent irrigation.

image from farm1.staticflickr.com

image from farm4.staticflickr.com

My presentation on irrigation water quality

Yesterday I taught a seminar about irrigation water quality.

Here are some links related to that presentation.

Field day poster: 5 grass varieties, 3 levels of salinity, and a month to grow-in -- or not

This poster for today's field day describes what happened when we planted five grass varieties as stolons and then supplied irrigation with different amounts of salt in the water. I think two things might surprise you. First, some of the grass varieties, including a particular manilagrass (Zoysia matrella), can reach full coverage in about one month after planting. Second, irrigation with salty water, so long as enough is applied, doesn't slow down the growth of many warm-season grasses.

image from c1.staticflickr.com

When the grasses can grow like this, it shows that managing the problems with water quality are closely tied to the quantity of water supplied. I will be talking more about this tomorrow when we are back for another day of seminars.