December 21, 2010 By Mike Jiggens
TAKINGâ€ˆthe time to ensure traditional maintenance practices are
followed without skimping on costs will promote healthier, safer
athletic fields, attendees at the 23rd annual field day of the Sports
Turf Association were told in September at Cambridge, Ont.’s Optimist
Dr. John Sorochan, associate professor of turfgrass science and management at the University of Tennessee, acknowledged provincial legislation in both Ontario and Quebec has made it increasingly difficult for sports turf managers to control pests on their fields, adding if certain measures aren’t taken, a dramatic rise in athlete injuries will occur.
He said player safety is of foremost concern when managing sports turf, noting 25 per cent of all injuries to athletes are a direct result of a field’s condition. In the United States, 31/2 million children under the age of 14 are hurt annually while playing on sports fields, with one-quarter of those injuries occurring due to poor field conditions.
Little data exists to support the claim that pesticides used on athletic fields are harmful to humans, Sorochan said, singling out 2,4-D as an example.
“But there’s data that shows children get hurt on athletic fields if you’ve got poor playing surfaces. I’d be really interested in seeing in Ontario over the next few years if people start tracking injuries of children playing on athletic fields where the surface has now become jeopardized for safety.”
Sorochan, a native of Calgary, Alta., said one of the leading health problems currently existing in the United States is obesity, and, if children continue to sustain injuries while playing on substandard fields, they may be inclined to give up on physical activity to the point where they will contribute to the obesity problem as adults.
“So it’s important to keep athletic fields as safe as possible so we can be active for the rest of our lives.”
Not being able to use traditional pesticides on sports fields in Ontario and Quebec and in several municipalities in other provinces forces sports field managers to pay extra attention to other practices to help alleviate the threat of pests and promote safer playing conditions.
One such practice is mowing, Sorochan said. Probably the most labour-intensive of all turf maintenance practices, it is actually a beneficial stress on turf because it stimulates new shoot growth, enabling fields to fill in.
Although reel mowers promote a higher quality of cut than rotary mowers, the drawback to their use on sports fields is that they tend to spread large patches of crabgrass if the weed is present. In situations where there is extensive crabgrass cover, rotary mowers should probably be favoured, he said.
Regardless of the type of mower used, ongoing maintenance of the machines, including blade sharpening, adds to the overall labour intensity of mowing. This often results in restricted budgets for many municipalities which will limit mowing of sports fields to once a week.
By mowing twice a week, however, sports turf managers can increase their percentage of turf cover in terms of the number of plants per square metre, Sorochan said.
“You can improve the density simply by mowing more frequently. Mowing is important to keep that turf as dense as possible to maintain a dense surface and ultimately a safer playing surface. Mowing twice a week vs. once a week, you can reduce some of the weed competition. Weeds don’t cause bad turf. Weeds are a cause of bad turf.”
The more a field is used, the greater the wear which subjects the field to weed invasion.
“You want to favour conditions so that the grass can recover as quickly as possible.”
Irrigation is another practice which needs to be conducted with precision, Sorochan said.
“Don’t water beyond field capacity,” he warned.
Too much water causes anaerobic conditions, leading to plant stress and a surge of weeds. Frequency of watering will depend on the season.
Automatic sensors in the ground is a technology designed to help sports turf managers apply the proper amount of water and when best it should be applied. Based on the volumetric water content of a soil’s root zone, the sports turf manager can look at when the turf begins to wilt and determine how much water is needed, setting up the system so that the water won’t be turned on until a point is reached when it’s too dry, and won’t allow for further watering beyond optimum conditions.
“Technology has come a long way over the past couple of years,” Sorochan said, adding significant cost savings can be realized when not being able to overwater.
Before sports turf managers put together a fertility program for their fields, they should have their soils tested to determine what is happening in their roots zones and to recognize any deficiencies, he suggested. This will help answer such questions as, “Is it necessary to spend a lot on phosphorus fertilizer if there’s already an abundance in the soil, or potassium?”
Soil tests won’t give proper nitrogen information since it’s always changing in the soil, Sorochan said, but they will pinpoint how much phosphorus, potassium and other nutrients need to be applied and determine the soil’s pH level.
Sorochan warned his audience that they will get what they paid for when it comes to fertilizer selection. Fertilizers tailored to the agricultural market tend to include a wide range of particle sizes and distribution whereas fertilizer produced specifically for use on turf will offer better, more uniform distribution.
“It’s tough to fertilize turf like a cornfield,” he said. “You don’t want big chunks where you can get spottiness. You want a nice uniform cover when you fertilize.”
Sports turf managers have options for the type of fertilizer they wish to use. Water-soluble sources of nitrogen will dissolve readily in water and will be immediately available for the plant to take up, but they shouldn’t be overapplied due to their potential for burn.
If leaching is a concern, slow-release fertilizers won’t have the same propensity for leaching as water-soluble varieties.
Thatch on sports fields has both its advantages and disadvantages.
“A little bit of thatch is good. It adds some resiliency and cushioning effect.”
While thatch may provide a softer playing surface for athletes and reduce the potential for injury, a thatch layer exceeding a half-inch in thickness can lead to problems.
The combination of dead or decomposing or living rhizomes, stolons and organic matter which accumulate above the soil surface yet below the main turf material can lead to mower scalping as the wheels wil sink downward, bringing the cutting deck dangerously close to the surface.
Kentucky bluegrass is a prolific thatch producer compared to perennial ryegrass which is a low producer.
“When that organic matter’s production is faster than the rate it can decay, that’s when we start to get a buildup of thatch above the surface.”
Vigorously-growing species or cultivars will contribute that much more to thatch problems, Sorochan said.
Acidic conditions will lead to thatch conditions as well as decreases in earthworm populations. Typically, when earthworm populations decline, thatch increases.
Thatch can become hydrophobic and inhibit the absorption of water, repelling it and creating drying problems. On the positive side, however, thatch can moderate crown temperatures and provide resiliency.
Managing thatch can be achieved by topdressing, core aeration, the application of light and frequent controlled-released nitrogen, and vertical mowing.
Compacted sports fields are a leading contributor to athletic injuries. Conditions which favour compaction include soils high in silt and clay as well as heavy user traffic.
“Roots need to respire,” Sorochan said. “They need to breathe like you and I do. They need oxygen. If you have a compacted soil, you reduce the big, air-filled pore spaces in that soil for the roots to respire and adequately grow.”
Taking the right measures to address compaction will help keep knotweed at bay. The weed favours compacted field conditions.
Vibratory slicing is one effective way to open up the airways beneath the surface and better manage compaction, Sorochan said. The “drill and fill” technique also allows for better water infiltration. The process is slow, however, and completing an entire sports field will take time.
Sorochan endorsed topdressing as a means to improve a field’s recovery from wear and help stave off compaction. He said if a sports turf manager has a native soil athletic field and there is significant moisture, that moisture will tend to cause more wear on the turfgrass. By adding a little sand to the surface, it will help take away the surface moisture and reduce the potential for compaction to occur by providing more macropore air-filled space for the turf to grow and recover.
Too much sand applied, however, can backfire and lead to damage. Sorochan suggested a light topdressing or “dusting” of about an eighth of an inch.
The use of crumb rubber on athletic fields has its pros and cons, he said. The material is ideal for protecting the crowns of the turfgrass plants and helps heat up seed for earlier germination in the spring, but too much of it can hinder turf growth in areas where there is a lot of wear.
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