Viridescent - the Asian Turfgrass Center blog

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:

@asianturfgrass Any need to account for an input through irrigation water? Average here is 110ppm for Na. Impact reflected in soil test?

— David Kuypers (@gcscuttenfields) March 19, 2013

That is an excellent question, and this chart for Na shows what may happen with that element. Let'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

Sand 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 (EC_w) of the irrigation water and of the soil (EC_e). Sodium can be a major contributor to that, and if the EC_e 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

Today 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.

I 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
• Google Terms of Use • Data Policy

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.

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.