Tips From The Pros

GOTCHA MEDIA LOVES PLAYING SURFACE STORIES

One thing we know about playing surfaces at high profile events. Everyone has an opinion, and it’s almost always extreme. For some reason, we go over the top in our opinions about playing surfaces. Every playing surface is either the best or the worst ever in history. I suppose that the surface is part of sports and fan is short for fanatic.

‘Field of Screams’ news pieces have been around forever, in fact you have not arrived as a groundskeeper or a sporting facility until someone has done an unfair and factually incorrect media piece about your playing surface. And it seems to be getting worse with today’s world of sub-media, all that needs to happen is a tweet and maybe a picture and were are off to the races. The story gets legs when the ‘dominant’ media report that ‘it has been reported’.

Almost always, the games go on and it’s no big issue in the end. The ‘story’ dies a quick and painless death.

But there is a larger issue in both stories that is rarely discussed. Why do we assume that the intentions of the sport’s governing bodies are always greedy and wrong? The USGA has been trying to get people to realize that wall-to-wall irrigated, green, high-quality turfgrass at a golf course will no longer be practical as we face growing water and irrigation issues, especially in the western US. Brown is the new green; that’s the mantra and they are looking at the future growth of the game. In soccer, FIFA realizes, like many, that there are climates and economies in the world that will not practically support natural grass surfaces suitable for play at all levels. Artificial pitches have to fit somewhere in the equation. Whether or not you agree with these positions is beside the point. Both organizations have not done a very good job at getting their messages out. Like too many, they combat the 24-hour made-you-look media of this new millennium with last century’s tactics. When the click-hungry gotcha media throws out a story, a savvy organization will have mechanisms in place to deliver a factual response, rapidly. That’s how it has to work in today’s new world where everyone is a journalist.

Turf Tips 101: Dealing with the Heat

June ushers in the first of the really hot summer days for many field managers and this brings a whole new set of challenges to the job. While the sizzling temperatures may generate aggressive and healthy growth in warm-season grasses like Bermudagrasses that are used in southern climates in the US, there are few other benefits to a sports field management program. In fact, it can be the most challenging time of year for many considering the stresses to the grass and fields from an accelerated events schedule. Cool season grasses will begin to suffer from chronic heat stress, and the turf managers can also get worn down in the summertime heat.

Generally, we know when we are heat stressed, but it’s harder to tell when your cool-season grass is heat stressed. It’s like the frog that is set in slowly warming water, he doesn’t realize anything is wrong until the damage is done. In turfgrass systems, it takes time to realize the full effects of chronic heat stress. Unlike an acute heat stress even from a single episode of super-optimal temperatures, chronic heat stress (CHS) is more insidious and slow. Essentially, this is because chronic heat stress involves the heating of the soil temperatures as well as the ‘boundary layer’ temperatures in and nearly above the turfgrass canopy. A hot boundary layer above ground with a cool soil is rarely much of a concern, within reason. With a relatively high specific heat capacity, the soil warms over time and the effects start first in the roots before showing signs above ground. This can take several weeks to a few months do fully develop and express itself and by then, much of the damage has been done. Rarely killing the turfgrass, the result is typically a weakened turf that will recover when lower temperatures return. But in a sports field, this mid-late summer phenomenon is compounded by the significant stresses from a heavy event schedule and a bevy of games.

The optimal range for cool season (C-3) grasses is generally reported as 60-75° F (15-24° C). But that doesn’t mean your grass dies above or below these temps, it’s just the optimal part of a large temperature adaptability range of grasses. In my experience, once your top 2-3 inch soil temperatures begin reaching above 70° F (21° C), get ready to notice a slow decline in the general vigor of the turfgrass in its resiliency and look.

There are several strategies for combating CHS in cool-season turfs, and the key thing to remember is that most work best when started early, before the grass gets to the chronic heat stress point. Bring the turfgrass into a warm/hot summer period in optimal health reduces the risks of CHS and its severity. Spring tactics like core aerification and other playing surface invasive practices will help promote a stronger root system able to better mine water during hot periods that will be used in the leaves for transpiration cooling.

Different grass species vary in their tolerance of heat stress. Tall fescue (Festuca arundinacea) is considered “good” in heat hardiness amongst the cool-season turfgrass used in sports field applications. However, some question the quality of a TF surface and it is not generally used in high-profile fields. Kentucky bluegrass (Poa pratensis) and perennial ryegrass (Lolium perenne) provide superior playing surfaces and are the most commonly used species of cool-season grasses on sports fields. Both rate as “medium’ in heat tolerance, while common weedy grasses in highly managed cool-season turfgrasses like Annual bluegrass (Poa annua) and roughstalk bluegrass (Poa trivialis) are regarded as “poor” and “very poor” respectively.

Even within the more predominate C-3 sports field grass in the US, Kentucky bluegrass, there are significant differences between varieties. The heat tolerance is sometimes scientifically evaluated and reported in university research and/or the NTEP (National Turfgrass Evaluation Program) trials. Be cautious when comparing heat tolerance reports for different grasses. There is a critical distinction between heat avoidance and heat tolerance. Transpiring water from its leaves helps cool a plant and the immediate surrounding air. This is an example of a plant “avoiding” heat stress. This mechanism can help a plant in a relatively hot but dry climate. In a hot/humid environment, this cooling mechanism doesn’t work as efficiently. Heat “tolerance” is the plants adaptive ability to function better physiologically in a super-optimal temperature, regardless of its transpirational cooling opportunities. The bottom line when studying turfgrass evaluations for heat tolerance is to get data from a location with a similar climate as yours. If you live in a hot/dry climate, look at trials conducted in a hot/dry climate to choose the most appropriate varieties.

Wet, saturated soils heat up more efficiently than do drier soils. Good internal drainage in your soil promotes a cooler soil and a healthier turfgrass plant. Well-draining soils promote healthier roots able to better mine soil water for natural plant evaporative cooling above ground.

Stagnant, calm air aids in the heat build-up we are trying to minimize. Anything you can do to promote better air movement over the turf will help with chronic heat stress significantly. If you have ever been on a hot, artificial turf field on a sunny day, you’ll notice the effect of air movement quite dramatically on temperatures. The slightest breeze can really cool things down. As such, large fans can help, especially on the worst affected areas of the field.

Don’t over fertilize with nitrogen. Keep it slightly lean in the hot summer months. This will help the carbohydrate balance between the roots and leaves and stress the grass less in super-optimal temperatures.

I believe that tidal kelp products help with chronic heat stress. I think the emerging plant elicitor technology shows great promise. We are now beginning to better understand plant stresses and how to “pre-condition” the plant to them.

You can find every opinion possible in the literature about the effects, or lack thereof, of supplemental potassium applications for improving heat stress resistance on turfgrasses. My take is, that a reasonably higher level of soil potassium (K), especially in sand rootzones, is helpful during the hot and cold times of the year. I believe that potassium is just too important to water relations and thus cooling and stomatal responses that it’s a good idea to match your total K20 amounts to your nitrogen amounts when applying fertilizer. There are those who would disagree, but since potassium fertilizers pose a relatively low risk to water systems compared to nitrogen fertilizers, I say keep things in the high range when it comes to soil test reports. But remember, more is not better and there are limits.

Raising your cutting height, within practical limits will aid in chronic heat stress issues, but it is not always practical during a season of games and if you can’t wait until cooler temperatures arrive before lowering them back down again, you can make things worse in my opinion. It’s pretty rare these days where a field has adequate rest during the hot summer months to allow for needed recovery time when raising and lowering mower heights. Aside from maybe a school field that is not used in the summer months, I am not a big fan jumping up and down on mowing heights, especially changes of more than ± 10% of the normal adjusted-to length. Diseases love heat-weakened cool-season grasses. You want to increase your turfgrass monitoring up to twice-a-day for disease in prolonged very hot/humid conditions. Ken Mrock, the venerable Chicago Bears groundskeeper used to tell me that when heat and humidity add up to 150, watch out. Just know that there are also many cooler weather diseases you want to be watchful for too.

Photorespiration is why your cool-season grass quality tends to decline during periods of hot weather. When temperatures above ground begin to raise above about 86° F (30° C), cool-season (C-3) grasses undergo a process known as photorespiration. Simply put, the stomata in the leaves begin to close to conserve water. CO2 uptake is reduced compared to O2 uptake. Photosynthesis, or the plants making of ‘food’ declines rapidly, especially when temperatures exceed about 90°F (32° C). Yet the plants respiration rate, the burning of carbohydrates or ‘food’, remains steady or even grows in these hot conditions. Basically, the cool-season grasses begin to slowly starve in high temperatures and need to rely on their carbohydrate reserves in the roots. Once these reserves are depleted, turf decline quickly follows. Because of their different metabolic pathways, warm-season grasses like bermudagrass do not suffer from photorespiration.

This is why the evaporative cooling effect of a light misting application of water called syringing can be of the best ways to cool heat stressed turf. The idea is to minimize the time each day that the turf is undergoing photorespiration stress. However, the evaporative cooling effects of syringing do not work nearly as well as the humidity raises and is generally only practiced in drier climates.

Resources of the Month:

Field of Schemes is a companion site to the book of the same title. If you are interested in the publically-financed stadium game, this site keeps up to date on current news with a critical eye.

An interesting piece in Smithsonian.com about the evolution of the modern American football field over the last 100 years.

The STMA and the SAFE Foundation have produced three basic field evaluation videos aimed at the coaches, athletes, parents and other stakeholders in athletic field quality. Watch soon for a new fourth video on baseball/softball fields.

End Quote:

Burn down your cities and leave our farms, and your cities will spring up again as if by magic; but destroy our farms and the grass will grow in the streets of every city in the country.

William Jennings Bryan