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June 2013

Making use of nutrients in the soil

Roots_soilIf the amount of an essential mineral element such as potassium or calcium is adequate in the soil, the grass can obtain all that it requires from the soil, and fertilizer applications of that element will not be required. Soil nutrient analyses (soil tests) are conducted to determine if an element is required as fertilizer, or not, and if it is required, in what amounts. The MLSN guidelines provide the newest recommendations for what can be considered adequate.

But there is more to look at than just the amount in the soil at any one time. The nutrient content in the soil is dynamic. Waterfall charts are a quick way of looking at the inputs (starting amount in the soil, fertilizer applied, amount in irrigation water) and losses (plant uptake and harvest through clippings, leaching) to give an idea of the magnitude of each of these amounts.

I previously made waterfall charts for two essential elements, potassium and calcium, and one for an element we wish to manage below a certain level in the soil, sodium. Those charts all used units of parts per million (ppm), which is what soil tests and irrigation water are reported as, but usually not what one thinks of when applying a fertilizer or harvesting grass clippings.

I have made a new series of charts, with potassium and calcium both shown in three different units of measure: ppm, grams per square meter, and pounds per 1000 square feet.

First, let's look at calcium. The horizontal blue line represents the MLSN guideline for that element. When the element is present in the soil above the MLSN guideline, the grass can obtain enough of that element from the soil, without supplemental fertilizer applications.

Ca_ppmCa_gramsCa_pounds

This is based on estimates for Bangkok, where a bermudagrass green may produce about 900 grams of dried clippings per square meter each year, containing on average 0.45% calcium, and where 600 mm of irrigation may be applied each year, with a calcium content of 20 ppm. For this situation, the amount in the soil is above the MLSN guideline, and no calcium is required as fertilizer, because all of the plant requirements can be met by the large reservoir of available calcium in the soil.

For potassium, it is a bit different. There is less in the soil, and the grass uses more, and these charts show that the plant uptake is more than the starting amount in the soil. Fertilizer, in this case, is required to keep potassium above the MLSN guideline. These charts for potassium are based on 900 grams of dried clippings per square meter per year, with a 2% potassium content, and 600 mm of irrigation with a potassium content of 5 ppm.

K_ppmK_gramsK_pounds

These types of charts can be modified to show the mass balance for any element, because the starting amount and the annual inputs and losses of an element will be different for every location.


Irrigation of Bentgrass Greens in Summer: handouts from seminar

Irrigation_handout_jp 201306_irrigation_handout

These handouts, in English and in Japanese, were prepared for a seminar I gave at Takarazuka Golf Club. 

The topic was irrigation of creeping bentgrass greens in summer, and I discussed soil moisture content, how frequent irrigation can actually be used to maintain a lower soil moisture content than infrequent irrigation, how I would not syringe greens to cool them if I were a greenkeeper today, and just how much the soil and surface temperatures change when ice, ice water, and tap water are applied to creeping bentgrass in summer.

I also showed some video clips of water movement in soils.


Turfgrass Mystery: why is there a ring of green grass around the collar?

green grass in June near Tokyo

This turfgrass mystery is illustrative of a couple of interesting points. These will be explained once the answer is given. This photo was taken in early June, 2001, at a golf course in Japan, near Tokyo. At right is the collar of the green, mown at 12 mm (1/2 inch). In the center is a band or ring of particularly green grass, and at left the grass is more yellow. At the right side of the photo, the grass condition is basically uniform, but at left there is the green grass and the yellow grass.

Can you identify what has caused this green band of grass, and why the grass at the left is yellow?

This was solved without too much trouble.

It was correctly pointed out that this must have something to do with fertilizer, with the green ring of grass responding to fertilizer that had also been applied to the green. But that is not all there is to it. 

The overlap of fertilizer didn't stop right where the grass turns from green to yellow. The yellow and shorter grass at left is japanese lawngrass (Zoysia japonica), and the grass at right is primarily perennial ryegrass (Lolium perenne). The fertilizer overlap extended into the zoysia. Because of the temperatures during this season, the ryegrass could use the nitrogen, and did, while the temperatures were too cool for the zoysia to make much use of the extra nitrogen.

At this interface between warm-season (Zoysia japonica) and cool-season grass (Lolium perenne), one grass was able to use the applied nitrogen, and the other could not. For the three weeks leading up to the date of the photo, I have calculated the daily growth potential, based on the actual temperature in 2001. This plot shows just how good the weather was for the ryegrass, and how relatively poor the weather was for the zoysia.

Gp_2001
In fact, the average cool-season (C3) growth potential in this span was 0.96. For the warm-season (C4) grass, the growth potential never got above 0.5, not even for 1 day, and the average growth potential was 0.29. For more information, see Explaining the Turfgrass Growth Potential.


Monthly Turfgrass Roundup (May 2013)

Following the lead of Simply Statistics, Revolution Analytics, and Newley.com, who often post lists of interesting articles, I will list here articles from the last month that are likely to be of interest to turfgrass managers in Asia:

Manilagrass (Zoysia matrella) may be the best choice for links-style goling conditions in Southeast Asia

Turfpath, a new app which allows turfgrass managers to share information about active pest problems, is available for free installation from Google Play and the App Store

All handouts and presentation slides from Sustainable Turfgrass Management in Asia 2013 are available for download. So are the handouts and slides from the 2010, 2011, and 2012 conferences. Be sure to mark your calendar for 10 to 12 March 2014 when this conference will be held again at Thailand.

Paul Jansen suggested that Vietnam, and Danang in particular, may be the best golfing destination in Asia. I countered with my choice of Hokkaido for the summer, and Thailand for the winter. What is your favorite destination?

One of the fun things about being a golf course superintendent is having the chance to test products and practices

This video, from a presentation made at Thailand on 7 May, covers the topic of Understanding Data Use for Turf Management

There is a big difference in temperature between transpiring and non-transpiring grass

The new Flickr design is beautiful. Did you know you can see more that 600 photos of turfgrass in Asia here?

Precision now offer a firmess meter, the same one used to measure green firmness for PGA Tour events. Here is Paul Vermeulen with a video showing how easy it is to measure the green firmness with this meter.

The amount of photosynthetically active radiation (PAR) has a huge impact on which grasses grow well, where. This new chart shows there is a big difference in PAR during warm weather between North America and Asia.

Every professional turfgrass manager should be able to answer this question about Tifway hybrid bermudagrass. Do you know the correct answer?

The ATC Turfgrass Information page was updated, now with more than 25 articles available for download

An interesting article at the Fine Golf website includes a quote from me about the Greenstester and making more putts

For more information, subscribe to this blog by e-mail or follow with an RSS reader - I use Feedly. Or follow @asianturfgrass on Twitter.


Summertime syringing to cool bentgrass greens: I wouldn't do it today

This question last month prompted an extensive discussion about the effectiveness of syringing greens. When I was a greenkeeper, I used to syringe* greens on hot summer afternoons. But more recently I've had a chance to study many experiments that have been done about syringing, and knowing what I know now, I wouldn't syringe today. Here's why.

habu_cc_9_green

I'll highlight four experiments that have looked at this, and you will see there is one common theme. 

Effects of Air Movement and Syringing on the Microclimate of Bentgrass Turf by Duff & Beard (1966): 6.4 mm (0.25 inch) of irrigation, an application of more water than we would consider syringing today, was applied to creeping bentgrass at noon. The canopy temperature in the afternoon seemed to be reduced somewhat (1 to 2°C) by this midday irrigation application. However, there does not appear to have been a control treatment to which water was not applied. This makes it difficult to be sure of the exact effect, but the addition of a substantial amount of water did decrease temperatures.

Syringing Effects on the Canopy Temperatures of Bentgrass Greens by J.M. DiPaola (1984): Eight rates of irrigation were applied, ranging from 0 (a control) up to 5.5 mm, at two different times, 11:00 and 13:00. The results of the experiment by Duff & Beard could not be duplicated. When 1.4 mm or more water was applied, there was sometimes a reduction in canopy temperature 30 minutes after the syringe, but that reduction never extended to an hour (even when applied water had a much lower temperature than canopy temperature). The reduction in temperature, which averaged 0.7°C, seems to have been greater when more water was applied. The conclusion? DiPaola wrote:

In summary, under the conditions of these studies, bentgrass canopy temperatures were not markedly affected by varying the volume or timing of syringing applications. Therefore, in the absence of wilt, the routine syringing of bentgrass greens must be reevaluated given the substantial economic cost of this procedure from the standpoint of water and labor alone.

Syringing: Does it really help? by Peacock and Bennett (1996): A syringe treatment (1 mm) and a hand-watering treatment (5 mm) were made at 13:00. Canopy temperature was initially reduced, but after 30 minutes was back to the same as the control plot to which no water had been applied. The turf quality was better in the syringed and in the hand-watered plot than in the control plot. They concluded that:

Hand-watering treatments consistently keep creeping bentgrass at higher leaf water potentials throughout summer. They also provide a more favorable photosynthetic and growth response and produce a plant less prone to disease and traffic stress ... After midday, consistently monitor your turf to determine whether it needs supplemental irrigation.

 

Handwatering
Handwatering a creeping bentgrass green during summer at Shanghai Links Golf & Country Club


In another article about the same experiment, they elaborated, writing:

30 minutes after application, canopy temperatures were back to control plot levels. Therefore, hand-watering and syringing treatments do not provide an extended cooling of the turf canopy, but rather improve water status of creeping bentgrass, as indicated by higher leaf water potentials.

Fan and Syringe Application for Cooling Bentgrass Greens by Guertal et al. (2005): This study looked at soil temperature at the 1.3 cm depth. Syringing caused a small decrease in the maximum soil temperature, but also caused the mean time each day with soil temperature > 27°C to increase. Fans were more effective than syringing in cooling the soil, and fans combined with syringing were the most effective.

What's the common theme? Syringing doesn't seem to have any magical effect, although air movement, or fans, do! Ensuring that the grass is supplied with enough water will optimize turfgrass performance.

chart of soil moisture content under two irrigation regimes

I wrote about this previously, suggesting that applying the right amount of water when the grass needs it is the most important thing to consider. Focusing on syringing, or deep and infrequent irrigation, or light and infrequent irrigation, all distract from the most important point. If the grass needs water, the best time to apply it is now. If the grass is going to need water this afternoon, then we can try to anticipate that by applying water in advance, to increase the soil moisture content. 

What would I do if I were a greenkeeper today? I wouldn't even think about syringing. Rather, I would:

1. Monitor turf conditions and soil moisture content. If there are places where water is required, I would apply water immediately. If I could anticipate that water would be required later in the day, I would apply water in advance, if I could, to prevent that stress.

2. Use fans if I could. 

3. Focus on ensuring that the grass is supplied with the right amount of water. 

When using the word syringe, I mean the application of a small amount of water to the turfgrass leaves for the purpose of cooling the surface. This will necessarily be less than 0.2 mm of water (less than 200 mL/m2). When any more water than this is applied, I will no longer use the word syringe, but instead use the word irrigation, by which I mean (from Beard, 2005) the intentional application of water to the soil, usually for the purpose of supplying water to sustain green plant growth.


Explaining the Turfgrass Growth Potential

Growth_potential_fact_sheet
This fact sheet provides an overview of the turfgrass growth potential (GP), explaining what it is, how it is calculated, providing examples of estimated plant nitrogen use based on GP, and much more, including suggestions on how the GP can be modified and extended. 

The GP is an index of the influence temperature has on turfgrass photosynthesis and growth. A simple and important extension of GP is using it to predict turfgrass nitrogen use. Ensuring that the grass is supplied with adequate amounts of nitrogen during the time when it can photosynthesize most efficiently will ensure that a maximum amount of carbohydrates are produced, leading, one expects, to a more extensive root system and healthier turfgrass plants.


For irrigation, which is better? Deep and infrequent, or light and frequent?

chart of soil moisture content under two irrigation regimes

That's a bit of a trick question, because the answer I give is: neither. What one wants to do is apply the optimum amount of water to the turf, and that can be done by light and frequent irrigation, or it can be done by deep and infrequent irrigation. This chart illustrates how soil moisture may change over the course of a month when two different irrigation regimes are used.

The optimum amount of water varies, with grass type, season, soil, type of surface one tries to produce, weather, type of irrigation system - these and other variables form an extensive list. But one thing that is consistent is that at any one time, for any one location, there will be an optimum amount of water, and achieving that, I suggest, should be the main focus, rather than focusing on how frequently water is applied.

Atc_irrigation_greenAt the Asian Turfgrass Center, we followed this approach in the maintenance of more than 50 varieties of grass. I probably would have tried to apply a lot of water, to fill the soil to field capacity, and then allowed the grass to use much of that water, before irrigating again - this is the deep and infrequent approach - but we had a small irrigation pump and it was easier for us to apply just enough water to meet the grass requirements. 

In a discussion with Dr. Doug Soldat from the University of Wisconsin, he explained clearly that one could actually maintain a drier soil, one that can supply just the amount of water the grass will use, while still maximizing the amount of air in the soil, not with infrequent irrigation, but rather with frequent application of just the right amount of water. Since then, I have focused more on ensuring the right amount of water is available to the grass, rather than what the frequency of irrigation is.

And in so doing, I have often been surprised at what a fine surface is produced, and in many cases a verdant one, even in soils that are maintained at a low volumetric water content (VWC). 

Roots_novotek_atc
Roots of Novotek hybrid bermudagrass maintained with light and frequent irrigation at a volumetric water content of less than 15%