Does sandcapping affect playability? And does species selection?

I get to talk about two of my favorite topics today. In our 1 day seminar on designing, building, and maintaining golf courses, course architect Paul Jansen will be speaking about 3 main topics:

Where do I come in? I'm going to hone in on the ground contours part, and discuss how the soil and grass conditions affect how a ball will bounce and roll. One can design and build all these great features, but if the sward isn't right, the playability won't be either.

A quick summary of my thesis is this -- sandcapping ain't so great because once one introduces a sand profile, the organic matter must be managed or it will fail. That happens by default for putting greens -- usually -- but almost never on 10++ hectares of fairway turf. And using grasses that don't die allows one to apply less N and water. That leads to firmer surfaces that are better to play on when one wants ground contours to be interesting.

Here are three ways to follow along.

First, my presentation slides are here:

Second, I shared a 2 page PDF handout at the seminar. Download it here.

Third, the above slides and PDF, along with links to all the articles and the video from the presentation, are in this online handout. For convenience, I reproduce all those links here:

Putting green construction and topdressing sand

Figure 1. A putting green being built using the USGA Recommendations for a Method of Putting Green Construction at Krabi, Thailand (January 2006)

When I teach about turfgrass maintenance, much of the discussion involves putting greens or other highly trafficked turf areas, because that is where most of the shots are played. And I am invariably asked questions about the type of sand to use, whether river sand can be used, or what type of amendments should be mixed with sand, and so on.

 These are important questions, and I have six things that I usually talk about when these questions are raised.

 1. Sand is a terrible medium for plant growth because sand has a low water holding capacity and low nutrient content. Plants, including turfgrasses, will generally grow better in soils containing some silt and clay than they will in sand. Of course, with regular maintenance, turfgrass managers are able to produce excellent turf in sand rootzones through the provision of water and nutrients to meet the plant requirements.

 2. However, a sand can be chosen that has two especially useful characteristics for high traffic turf areas. With the right particle size distribution, sands can be used that have a) a rapid infiltration rate, so that the surface is usable soon after a heavy rain, and b) resistance to compaction, even though there is a lot of traffic on the area. Infiltration rate and resistance to compaction — those are the reasons sands are used for high traffic areas.

 3. There are very specific recommendations for putting green construction provided by the USGA. This document, USGA Recommendations for a Method of Putting Green Construction, is freely available (http://bit.ly/USGA_green). These are sometimes called the “USGA specifications” and they outline everything from the depth of sand to the type of drainage to the sand particle size and various physical properties that the sand must have if the green is to meet the specifications set out in the USGA Recommendations document. Make variations from these Recommendations, and the green may still perform well, but please don’t call it a “USGA” green if the Recommendations are not followed.

 4. For topdressing sands, a good starting point is to look for sands that have physical properties that meet USGA Recommendations.

Figure 2. The same green, 8 years later, still performing well, which is what one expects when a green is built following the USGA Recommendations (May 2014)

 5. I don’t think the Method outlined in the USGA Recommendations is necessarily the best way to build a green, but it is one that works, and it is a way to build a green that many people understand and know how to manage. Figure 1 shows the construction of a USGA green in Krabi, Thailand in 2006, and Figure 2 shows the same green still performing well in 2014. That type of predictable result is what we expect when building a green to USGA Recommendations.

 6. If I were building a putting green for myself, and if I knew that I would be the one to manage it, I would probably build a green with some soil in it, with lots of surface drainage, with a slower infiltration rate than in the USGA Recommendations. But if I were building a green for someone else, and I knew that I would not be responsible for maintaining it, I would choose the USGA Recommendations. That way, the risk of unexpected problems is much reduced. 

 I encourage everyone to download a copy of the USGA Recommendations and to be familiar with the document. Many problems and confusions could be avoided by a broader understanding of this Method.

 I wrote this as part of a series for the Indian Golf Industry Association (IGIA) newsletter. For more about turfgrass information specific to India, see the ATC site www.in.asianturfgrass.com.

Relationship between soil moisture and turfgrass surface hardness

Yesterday there was a discussion on Twitter about soil moisture and surface hardness – I use the terms surface hardness and surface firmness interchangeably, but I usually prefer surface hardness.

In the report I prepared in August 2012, I included this figure, showing the relationship I measured between soil moisture (using a Theta-probe with 6 cm rods) and surface hardness (using a 500 g Clegg Impact Soil Tester).


One can't make an accurate prediction of surface hardness from soil moisture in general, because soil types and organic matter content vary, so the surface hardness can be quite variable across a wide range of soil moisture. It does seem that once soil moisture gets above 35% (by volume), it can be difficult to produce a firm surface.

However, for a consistent soil type and species and turf age, there can be a good relationship, as seen below. I'm sure that at many golf courses, there would be a consistent relationship between soil moisture and surface hardness. But that same level of soil moisture may not translate to the same level of surface hardness at another golf course. These data are from a golf course with seashore paspalum everywhere, and with a wall-to-wall sandcap.


Since I prepared the August 2012 report, I've collected another 647 paired measurements of soil moisture and surface hardness, this time measuring soil moisture to a 7.5 cm depth with the TDR-300. These results show a similar result to that measured previously. There is some relationship between soil moisture and surface hardness, but the location effect is important. One really needs to study this relationship at one's site, as Scot Dey is doing, to find how soil moisture influences surface hardness.



The same data (647 measurements collected after August 2012) from the chart above are shown by species in the chart below. 

soil moisture and surface hardness of golf course putting greens

For more about this topic, see:

Waterfall Chart of Putting Green Sodium Levels

I have decscribed how a waterfall chart can be used to show the nutrients that enter and leave a system, using potassium as an example. In that example, I did not show any input of potassium from irrigation water or rainfall, because I made the assumption that those inputs would be negligible. David Kuypers, the Golf Course & Grounds Superintendent at Cutten Fields in Guelph, Ontario, asked what would happen with sodium (Na) added through irrigation water:

That is an excellent question, and this chart for Na shows what may happen with that element. Na-waterfall-chartLet's look at a few components of this waterfall chart.

  1. The horizontal blue line at 110 ppm marks the MLSN guideline for Na. Unlike the 35 ppm level for K, which is a minimum guideline, this 110 ppm maximum guideline for Na is related to increased chance of rapid blight disease at soil Na concentrations above 110 ppm.
  2. I assume that we start with a Mehlich 3 extractable Na of 75 ppm. The annual plant uptake of Na is minimal for cool-season grass and I estimate it as being equivalent to a decrease in soil Na of 5 ppm. 
  3. I assume no Na is added as fertilizer.
  4. David said that his irrigation water has an average Na concentration of 110 ppm. That means for each liter of water, there are 110 mg of Na. If he adds 205 mm of irrigation water to the greens over the course of the season, that is equivalent to 205 L of water for each square meter. If we assume that the 22,550 mg of Na contained in those 205 L of irrigation water are distributed throughout the top 10 cm of the rootzone, and that the bulk density of the rootzone is 1.5 g/cm3, then that amount of Na will increase the Na in the system by 150 ppm.
  5. With this depiction on the waterfall chart, we can see that the amount of Na expected to be added with this much irrigation is twice the amount of Na that was in the soil at the start of the year. And we can make some comparison of the magnitude of each input and loss of Na from the system.
  6. However, sometimes there will be thunderstorms or other heavy rain events that will cause some leaching of that Na. Most of that Na will be remaining in soil solution; it won't be extensively held on cation exchange sites which would make it resistant to leaching. And if rain doesn't come, I assume that David will sometimes apply extra irrigation water to induce leaching of the Na. I assume that 130 ppm of the Na will be lost by leaching.
  7. With these assumptions, that leaves us at the end of the year with 90 ppm of Na in the soil, still below the 110 ppm MLSN guideline. And if we would go through the fall, and through the winter, we would expect no irrigation water to be applied, and some leaching to occur, and by the start of the next irrigation season, the Na would be reduced even more. In an arid climate, the Na would be expected to increase and increase, but in a humid climate, one in which precipitation exceeds evapotranspiration, most of the applied Na is expected to leach.
  8. We can see that if no leaching occurs, the addition of Na through irrigation will increase soil Na above the MLSN guideline of 110 ppm.

For more about maintaining soil Na below 110 ppm, see this document from PACE Turf.

Sand, Sodium, and Soil Structure

Abstract_sodium_hydraulic_conductivitySand rootzones are common the world over for golf course putting greens. Many athletic fields are also built with a sand rootzone, and in Asia, many of the tees, fairways, and even roughs are grown in a sand rootzone. Is sodium a problem for structure of these soils? The answer is a resounding NO. 

From the chapter Warm-season Turfgrass Fertilization by Snyder et al. in the Handbook of Turfgrass Management and Physiology, we learn that the "very sandy soils that often are used for golf greens and athletic fields have no structure and are largely unaffected by sodium."

Research presented at the 2012 Crop Science Society of America Annual Meeting by Obear et al. also showed that extremely high levels of sodium have no effect on the saturated hydraulic conductivity of sand rootzones. In this paper, Effect of Sodium On Saturated Hydraulic Conductivity of Sand-Based Putting Green Root Zones, sand, sand with various amendments, and a silty clay loam, were saturated with waters of varying sodium levels. The saturating solution with the highest amount of sodium had a sodium adsorption ratio (SAR) of 80, which is extremely high. 

But when the saturated hydraulic conductivity of the soils was measured, none of the sands, even those with the highest amounts of sodium, had a decrease in water movement through the profile

There are a few reasons to pay attention to sodium. In soils with appreciable levels of clay, soil structure can be negatively affected by sodium. If rapid blight is a possibility at one's property, then the soil sodium should be kept at less than 110 ppm. And one should be aware of the electrical conductivity (ECw) of the irrigation water and of the soil (ECe). Sodium can be a major contributor to that, and if the ECe approaches the threshold level for a species, steps should be taken to manage the soil salinity.

But sodium and soil structure in sand rootzones? That is not something to be concerned about.

Thai GCSA Meeting: Managing Organic Matter in Sand Rootzones

Vintage_meetingToday 110 people attended the Thai GCSA meeting at The Vintage Club near Bangkok. I gave a presentation on Putting Green Management and Putting Green Performance. This dealt with the main reason for poor performance of sand-based putting greens – the accumulation of too much organic matter.

The presentation slides can be downloaded here.

In my talk, I first mentioned the three main problems we have with turfgrass surfaces that are wet and soft because of too much organic matter in the soil.

  1. Mowing cannot be done properly and low mowing heights are impossible to obtain without scalping the turf.
  2. Ballmarks are excessively large and general playability of the course is not at an optimum.
  3. The probability of fungal diseases is increased.

I shared some data collected over the past year that shows an increase in soil moisture in a sand rootzone will usually lead to softer surfaces. We looked at a clip from a classic video of water movement in soils, to see what happens as water moves from a relatively fine-textured (sand + organic matter) layer down to a coarse-textured (sand without organic matter) layer, and then we discussed the four ways in which we can manage soil organic matter. Of these, I think the first two are the most important.

  1. Manage the growth rate of the grass to avoid excessive accumulation of organic matter, allowing the grass to grow at a rate sufficient to recover from traffic damage, but no faster.
  2. Apply sand topdressing to dilute the organic matter as it is produced. As a general rule, plan to apply at least 0.012 m3 sand/m2/year.
  3. Verticut (vertical mowing down to the soil surface) and scarify (vertical mowing that goes below the soil surface) to remove organic matter.
  4. Core aerify to remove organic matter, keeping in mind that tine size and tine spacing should be carefully considered to optimize the organic matter removal at each time of aerification. This will minimize disruption to golfers.

Vintage_meeting2I would like to thank the TGCSA for inviting me to speak today and for all the superintendents who attended. I spoke at a TGCSA seminar at The Vintage Club when I was just starting with the Asian Turfgrass Center in 2006, and it was fun to be back six years later, with about twice as many people in the room, to be presenting about things that we have learned, based on research conducted here in Thailand and in other parts of Asia.

For more information, see these documents:

A Report on Putting Green Performance Characteristics (Woods, 2012, Asian Turfgrass Center)

Aeration and Topdressing for the 21st Century (Hartwiger and O'Brien, 2003, Green Section Record)

Cultivating to Manage Organic Matter in Sand-based Putting Greens (Landreth et al., 2007, USGA TERO)

Why is there cool-season grass in Philadelphia and warm-season grass in Seoul?

We can look at temperature data for Seoul and Philadelphia and we find that the average temperatures throughout the year have almost complete overlap. So we might expect that with such similar temperatures on a month by month basis, the grasses used in those cities would be similar. But while the courses at Philadelphia are mostly cool-season grasses, what we find at Seoul are primarily courses planted to Zoysia japonica. Here is a dormant zoysia fairway near Seoul in early spring.


Why such a different choice of grass when the temperatures are the same? I suggest that it has to do with summer precipitation. 


From June through September, Seoul has a higher monthly average rainfall than does Philadelphia, and during the two hottest months of the year, July and August, Seoul has more than three times the rainfall, on average, than does Philadelphia. This combination of high temperature with high precipitation can be deadly for cool season grasses.

Customize the chart yourself to see data for other cities.

Data: korea • Chart ID: ATC_climate_chart_Korea

R version 2.15.0 (2012-03-30) • googleVis-0.2.16
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Try This Technique for Improving Drainage


It is always a challenge to manage areas with poor drainage, and on sandcapped turfgrass areas the drainage can be quite problematic once organic matter builds up over the sand layer. Topdressing and aerififying and verticutting can all be used to dilute or remove organic matter, but when the organic layer gets too thick, it holds a lot of moisture, negating the value of the sandcap and creating an ideal growing environment for weeds.

Sand_om_layer The image above shows how an organic layer develops on a sandcapped fairway, and the image at right shows how weedy species have colonized the surface of what was once a zoysia fairyway. The buildup of organic matter over sandcapped fairways is why I have often suggested that sandcapping is not an ideal way to construct a fairway. Sandcapped fairways require more maintenance and deteriorate over time. Topdressed fairways, on the other hand, require less maintenance and improve over time.

But no matter what type of soil you have, this tip from Larry Gilhuly at the USGA is one that might be useful for you. Have you ever encountered areas with excessive organic matter buildup that slows water from infiltrating into the soil? Gilhuly asks,

"Can this condition be easily fixed at no cost or should all of these locations have complete renovation? . . . Sand topdressing and regular aeration are used to help negate the problems of excess organic material, but often this is not enough. After testing several methods to dry these areas, Rich Taylor, CGCS, struck upon the idea of using cup cutters spaced every one to two feet to go as deep as possible. The excessive organic material and some soil is removed and replaced with sand. This change essentially creates multiple dry wells in the area. If the soil underneath has reasonable permeability, the results are fast and effective. Follow-up sand topdressing is then practiced to minimize future layers. In the past few years, previous wet areas around the greens are now gone by using this simple technique."

Read the entire article on the USGA website here.