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)

Golf Course Maintenance at Japan: week 2, core aerification with no clean-up required

The maintenance equipment used on Japan's more than 2,400 golf courses is usually the same as is used in other parts of the world, but sometimes the equipment is quite different – the Yanmar helicopter comes to mind.

Last week at Hokkaido I saw the self-collecting fairway aerifier in action, and was again surprised at how fast the fairways can be cored, and at how clean the finish is.

The cores are collected in central drums and are emptied in about a minute beside the fairway.

After that fast and clean coring of the fairways, sand topdressing is applied, and these creeping bentgrass fairways are better prepared for the upcoming summer season.


Ten Years Ago on a Golf Course in Japan: part 1


I was a golf course superintendent in Japan from September 2000 until August 2001. Now, ten years later, it is interesting to see some of the photos from that year and to remember what it was like. We were working with a maintenance crew of about sixteen people in July of 2001, and I think five people on the crew went on to be golf course superintendents themselves; two interns from the United States, and three of the Japanese crew. 

habu cc eighth hole 22 July 2001We had a great team. July 22 was a Sunday that year, and on Japanese courses then, it was not typical to have much afternoon or "twilight" play. Golf tended to be (and generally still is) a structured event, so tee times (Japanese courses usually do a two tee start, off #1 and #10) would generally be booked a few weeks in advance, with the last tee times usually set at midday. Even on a busy day, after 14:00 or so the course would begin to clear as the last golfers played their final nine holes. 

We were able to get a lot of work done on these afternoons. Soil tests of the fairways showed that the soils were low in magnesium and potassium. We were able to find sul-po-mag (0-0-22) from a Japanese agricultural supply company and apply it to fairways to increase the potassium and magnesium availability. And we had to do a lot of work to manage soil compaction, improve water infiltration, and stimulate growth on the bermudagrass fairways. At the time Habu CC was one of the few courses in Japan that used two passenger carts, and at which the carts were allowed to be driven on the fairways. We were doing about 4,000 rounds per month, all with carts driving onto narrow fairways of this course in the mountains of Chiba. So ten years ago today, we waited until the last golfers had moved off these holes and then worked until the sun went down.

habu tenth 22 July 2001

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.

Sandcapping or topdressing: which is better?

Woods_fwy_sandcap I have often advocated sand topdressing rather than sandcapping for golf course fairways and roughs. Why? Because sandcapping at the time of construction makes for a much higher construction cost, higher maintenance cost, and invariably leads to deteriorating playability over time. Conversely, a sand topdressing program provides better playing conditions, easier maintenance, and all for a much lower cost. I am not referring to drainage. Drainage is required for both a sandcapped system and a topdressed system. But sandcapping is not drainage.

Sandcapping a turfgrass area with 10 to 15 cm of sand has a high upfront cost and then forces higher maintenance costs as well, for that sandy rootzone will require more fertilizer, more irrigation water, and more surface organic matter management than would an area not sandcapped. And what happens if the organic matter is not controlled? See below. What used to be a fine zoysiagrass is now a mixture of cowgrass and sedges. A layer of organic matter built up at the surface creates a perfect growing environment for weeds that thrive in wet soils. And all that sand underneath? One might as well bury money in the ground. Once the organic layer builds up over the sand, there is no benefit whatsoever to having the sandcap.

Dr. Alec Kowalewski has recently published some intriguing articles that show just how effective sand topdressing can be as an alternative to sandcapping. Not only does he demonstrate the substantial cost benefits of a topdressing (or built-up over time sandcap) program compared to a sandcap installed at the time of construction, his research also shows how turf quality improves and drain line spacing can be extended when a topdressing program is implemented. 

"Preliminary findings from this research," he wrote, "suggest that as little as 1/2” (1.25 cm) of sand can be used to improve athletic field playability by substantially decreasing the surface moisture content." His results show that once 2.5 cm of topdressing sand has been applied, drain line spacing at 3.9 meters provided sufficient drainage and surface stability. After a 5 cm topdressing layer was established, and assuming surface slope is at 1% or greater, then drain line spacing could be extended to more than 6 meters while still producing the desired surface conditions.

For full details, see:

Kowalewski, A. R.; Crum, J. R.; Rogers, J. N. III. 2010. The built-up sand-capped athletic field system. MSU Turfgrass Science Program. April 7. p. 1-7.

Kowalewski, A. R., J. N. III Rogers, J. R. Crum, and J. C. Dunne. 2010. Sand topdressing applications improve shear strength and turfgrass density on trafficked athletic fields. HortTechnology. 20(5):p. 867-872.

Kowalewski, A. R., J.R. Crum, J. N. III Rogers, and J. C. Dunne. 2011. Improving native soil athletic fields with intercept drain tile installation and subsequent sand topdressing applications. Soil Sci. 176(3): p. 143-149.

Ballmark With sandcapping at the time of construction there is a high upfront cost, turfgrass and playing conditions that deteriorate, and there will be the need for a disruptive and costly renovation to remove the organic layer that will invariably develop at the surface. Planting grass onto native soils and then topdressing with sand results in lower construction costs, lower maintenance costs, and better playing conditions over time with longer intervals between disruptive renovation projects. It is the surface conditions that matter for the playing of sports on grass, and topdressing with sand is a proven method to create the desired surface conditions.

Field Renovation for the 2010 World Cup

World_cup_renovationI received this document with three pages of photos of the renovation process for 72 playing fields to be used for the 2010 FIFA World Cup at South Africa next month. Click here or on the photo at right to download the file (2 MB).

Ten fields will be used for the tournament matches, and the remaining fields are for training, as home practice fields for each of the 32 teams in the tournament, and there are even three fields prepared just for the tournament referees. The fields are mostly kikuyugrass, but for the tournament have been overseeded with perennial ryegrass to provide a vibrant green color and some wear resistance during the South African winter. The document about the field preparation is provided by Redexim as much of their equipment was used in the renovation and overseeding of the playing fields.

If I Were a Superintendent . . .

I would give this topdressing technique a try. Todd Pippin has written an article for the Green Section Record describing his five-day program of adjusting mowing heights and other tricks that can be used to allow topdressing sand to work its way into the canopy without excessive mower pickup.


The necessity of regular sand topdressing to dilute organic matter on golf course putting greens is unquestioned. The problem faced by those managing the turf, however, is that with low cutting heights on greens, the sand that is applied as topdressing sometimes gets picked up by the mowers on days succeeding the topdressing event.

Pippin's program (you really should study the article with full details) involves a grooming and mowing at 10 to 15% below the starting mowing height on the day of topdressing (for example, mow at 2.8 mm when normal height is 3.2 mm. The topdressing is followed by a heavy irrigation. On the day after topdressing, the mowers are set at a height 10 to 15% above the starting mowing height (for example, mow at 3.7 mm instead of the normal height of 3.2 mm). On days three, four, and five, the mowing height is gradually lowered. Pippin reports that this program allows topdressing sand to be applied with minimal disturbance to ball roll speed and almost no pick up of sand by the mowers. 

If I were a superintendent I would give this program a try. Sand topdressing is essential in maintaining adequate aeration porosity in the soil. If you have a chance, give this program a try and see how it works at your course.

Relieving Turfgrass Stress: Part 2, Air in the Soil

Aerify-habu-cc In a previous post I wrote about relieving turfgrass stress by ensuring that grass blades are cut cleanly. After ensuring that mowers are sharp and are mowing the grass at the optimum height, what is another way to relieve turfgrass stress?

Turfgrass stress can be reduced by ensuring there is enough air in the soil. Golfers don't like aerification and greenkeepers are often under pressure to skip aerification because on the surface the greens appear to be fine. But when there is not enough air in the soil, roots do not grow, and grass without roots does not provide a good playing surface for very long.

black layer in turfgrass soil profile

The black layer in the soil above is because of waterlogged conditions. Roots are not growing in the saturated soil, but can you see the old aerification hole in the center of the photo? Do you see that vertical strip through the soil profile with no black layer? Do you see the white roots growing in this aerification hole? When there is enough air in the soil (and I would suggest that about 25% air by volume is a good starting point), the roots can grow. The reason for hollow tine core aerification is to physically remove organic matter from the soil while allowing more air into the soil, and the reason for solid tine aerification is to introduce air into the soil. Organic matter in the soil creates small pores that hold a lot of water. Healthy turfgrass creates large amounts of organic matter, and this organic matter must be managed in order to maintain adequate air in the soil. For a look at some more photos of roots and aerification practices, click here.

The solution to the black layer problem or to the problem of too much organic matter in the soil is really a simple one: make more air in the soil. This is done by keeping the soil as dry as possible, by physically removing organic matter, by regularly topdressing with sand to maintain aeration porosity, and by venting or other types of solid tine aerification, as shown below.

So the next time you suspect your turfgrass may be suffering from too much stress, think of ways that more air can be introduced into the soil. More air in the soil is a sure way to reduce stress and improve turfgrass conditions.

Core Aeration of Putting Greens . . . how much is enough?

Aerification of golf course putting greens is the most disruptive maintenance activity, but it is also one of the most important. Proper aerification creates a healthy growing environment for turfgrass. That healthy growing environment is very important when we consider the stresses that a putting green is subjected to: traffic, low mowing heights, nematodes, diseases, low light conditions -- the list is extensive. But putting greens are also the most important area of any golf course. Turfgrass managers should do everything they can to create a healthy growing environment for putting green turf. 


I have written about the importance of filling core aeration holes with sand, and this video from Washington State University shows how water does NOT easily enter aeration holes that have collapsed at the surface. Coring holes must be filled with sand to get the desired effect.

Problem_green Everyone knows that coring is disruptive, but having bad greens is even more disruptive! Having an effective core aeration program is a key to having good greens, and at many of the courses that I see in Asia that have recurring problems with the grass on their greens, we can trace the problems back to a general lack of core aerification, and a subsequent accumulation of organic matter at the putting green surface.

So how much coring is enough? It depends on the course, but I say that at a bare minimum, there must be at least 10% of the putting green surface area removed each year and replaced with clean sand in the holes. Ideally there would be 20% of the green area removed, and if the ownership of a course wants to have good greens, they will find a way to get this done. Chris Hartwiger and Pat O'Brien, agronomists with the United States Golf Association Green Section, recommend 15 to 20% of the green surface area be removed each year. Courses in Asia that remove less than 10% of the green surface area by coring each year tend to have recurring problems with their greens. The exact amount of surface area to remove must be decided on a course-by-course basis, but you can be pretty sure that you need to remove between 10 to 20% of the green surface area annually.

I would never make an aerification without first determining how much of the green surface area will be affected. The calculations are simple. We know the tine diameter and radius and can calculate the area affected by one core using the formula πr2. The number of coring holes per unit area can be calculated based on the tine spacing used on the machine; tines on 5 cm x 5 cm spacing will give 400 holes per m2. So as an example, 10 mm diameter tines used to aerify a green on 5 cm x 5 cm spacing will remove 3.1% of the green surface area. Using 12 mm diameter tines on the same spacing will remove 4.5% of the green surface area. 


All other factors being equal, the key determinant of recovery time from aerification will be the tine diameter. Larger diameter holes take a longer time to recover. So for efficient aerification, with the least disruption to the golfer, removing as much of the green surface area as possible while still having the fastest possible recovery time, my goal is always to use the closest possible tine spacing and an approriate tine diameter. If you are able to set your aerifiying machine to a 2.5 cm x 2.5 cm spacing, there will be 1600 holes per m2! But keep in mind that it is not the number of holes on the green that cause a disruption to putting quality. It is the time the holes remain open without the grass growing back over them that actually causes a disruption to play.

Here are some tips for effective core aerification of putting greens:

  • Ideally you will remove cores from 20% of the green surface area each year.
  • Be sure to remove at least 10% of the green surface area by coring.
  • Do whatever it takes to fill the holes with sand -- coring holes that are not filled with sand only have a temporary benefit to the putting green quality.
  • Because small holes are very difficult to fill with sand (because of bridging of sand particles at the top of the hole), I recommend the use of tines at least 10 mm in diameter -- 12 mm or 14 mm are even better.
  • I always try to minimize the tine spacing, making the holes as close together as possible. This is the most efficient way to core aerify while minimizing disturbance to golfers.

Fill Aerification Holes With Sand


This video clip shows the way water moves into an aerification hole filled with sand all the way to the surface. Notice how the water does not penetrate into the aerification hole that was not backfilled all the way to the soil surface. The full DVD of Water Movement in Soils is replete with interesting demonstrations of how water moves in soils and is available for purchase from the Department of Crop and Soil Sciences at Washington State University.

It is important to understand how water moves into new and old aerification holes. When core aerification is done, the holes must be filled with sand. If holes are not filled with sand, the result, over time, may be counterproductive, as it may lead to more hydrophobic conditions in the soil. When holes are filled to the surface with sand, and then regular sand topdressing is applied (I suggest about 0.012 m3/m2, or 1.2 cm annually) to keep adequate air space at the soil surface, and when solid-tine aerification is used as well, then there will be adequate channels for water to move into the soil, there will be adequate air space in the soil, and turfgrass conditions will be improved.