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Winter Turf in Southern Regions

Preparing grass for winter football takes knowledge,
technology and skill–even in San Diego, Calif.
A groundskeeping professional shares his secrets with LSMP readers

By Steve Wightman, Stadium Turf Manager, Qualcomm Stadium






San Diego's Qualcomm Stadium is ready for Super Bowl XXXVII in January 2003. The dormant hybrid Bermuda grass of summer has been overseeded with ryegrass to insure a healthy green--which is highlighted here by mowing in alternate directions every five yards.


Unlike the colder northern states where the winter months bring freezing temperatures and brown dormant grass, most southern sates enjoy warm winter temperatures and green grass. Most athletic fields in the southern regions of the country contain warm-season grasses and experience a similar dormant period in the winter as grasses in the northern regions.

Warm-season grasses are chosen because of the superior wear tolerance that athletic fields demand. They also have the ability to recover quickly from the damages of wear and cleated traffic. As one might imagine, warm-season grasses also perform very well under the hot summer temperatures while the growth of cool-season grasses slows down in excessive heat.

The most widely used warm-season turfgrass species for sports fields include, Common bermudagrass (Cynodon dactylon), hybrid bermudagrass (Cynodon dactylon x Cynodon transvaalensis), Zoysia (Zoysia japonica) and Kikuyagrass (Pennisetum clandestinum). With proper maintenance all of these species hold up well under heavy traffic which makes them popular choices for athletic fields in the southern regions.

However, as mentioned earlier, warm-season grasses also go dormant during the winter months in most of the southern regions. Because field activity is as predominate in the winter as the summer most athletic fields are overseeded with cool-season grasses during the winter months. Overseeding allows a field to better support play during the winter by providing a certain level of wear tolerance and recovery along with some aesthetic appeal.






Soil pH is critical for maximizing nutrient availability to grass plants. Maintaining a soil pH of 6.5 to 7.0 (which is slightly acidic) lets grass easily absorb most nutrients.

The thick portions of colored bands below indicate healthy absorption rates.



Cool-season turfgrass species that perform well on athletic fields where high traffic occurs includes Kentucky bluegrass (Poa pratensis), perennial ryegrass (Lolium perenne) and Tall fescue (Festuca arundinacea).

Should I overseed or not?

The practice of overseeding can be beneficial in the short run but may prove costly in the long run both in terms of monetary costs as well as the cost of the field's inability to support heavy play in later years.

In order to benefit from the stronger characteristics of the warm-season grasses during the summer months the cool-season grasses should be removed when the warm-season grasses come out of dormancy in the spring. By removing the cool-season grasses the more desirable warm-season grasses are relieved of unwanted competition allowing them better performance under the very demanding pressures of high traffic. Various methods can be used to help remove the cool-season grasses from a warm-season grass stand. Selective herbicides are available to chemically suppress and eliminate cool-season grasses that are growing in a warm-season stand. However, extreme caution should be used to avoid excessive damage to the desirable turfgrass. It's best to contact a turfgrass professional for assistance in developing an herbicide treatment plan and always follow the directions on the chemical label.

In addition to chemical applications for removing cool-season grasses from a warm-season turfgrass stand, there are also cultural practices that can assist in this process. To transition out the cool-season grasses once the warm-season grasses are green and growing in mid-spring the maintenance program should reflect cultural practices that benefit the warm-season turfgrass stand. These beneficial practices include reducing irrigation, lowering the mowing height and prudently increasing nitrogen fertility applications.

Unfortunately, in most cases, the transition process can be costly in terms of dollars and field down-time which, in many cases, are reasons why some just leave it alone. Allowing the two turfgrass types to compete with each other throughout the year usually translates into the field succumbing to a predominantly cool-season turfgrass stand within a year or two.

On the other hand, not overseeding at all on high traffic sports fields most always results in a barren playing surface virtually void of any turfgrass cover since dormant turfgrass cannot repair itself.






A groundskeeper spreads perennial ryegrass over Qualcomm field as cooler temperatures arrive in October. The process will be reversed in the spring, when selective herbicides and/or treatments such as adjusting fertilizer and mowing height are used to eliminate the cool-season turf. Ryegrass seeding rates vary but for heavy-use sports fields 10 to 15 lbs. per 1,000 square feet is common.


So, overseeding warm-season grasses with cool-season grasses during the winter is not always an easy decision. It's a decision that should involve a comprehensive plan that addresses both the overseeding process and the transition process to maximize the benefits of both turfgrass types throughout the year.

Cultural practices

If a sports field has been overseeded with a cool-season turfgrass for winter play then the cultural practices should be adjusted to benefit that turfgrass species. Adjustments should also be made to compensate for the different climatic conditions that winter brings – shorter duration of sunlight, increased moisture from rain and a lack of evaporation as well as greater temperature variances, to name a few.

Irrigation

Probably the greatest challenge in maintaining athletic fields is managing the amount of water on the surface and in the root zone. For optimum playing conditions and turfgrass performance moisture management must be monitored daily and adjusted accordingly to reflect the ever-changing climatic conditions and field usage schedule.

The effects of too much water on a field result in destroying the integrity of the playing surface and inhibiting player performance. Too much water invites destructive pathogens and diseases that can quickly destroy a turfgrass stand. Most diseases (Dollar spot, fusarium, Helminthosporium and pythium, etc.) are a direct result of excessive moisture either on the leaf tissue or in the soil profile.

On the other hand, a lack of adequate irrigation can result in hard droughty surface conditions that also adversely effect player and turfgrass performance. A dry hard playing surface prevents good footing and results in skating and slipping and can increase injury risks.

The challenge of proper irrigation becomes even more pronounced when athletic fields are in constant use. Irrigation management, in many cases, usually involves applying just enough surface water to "get by" so as not to risk losing the stability and strength of the field surface that deeper irrigation can sometimes create. Deep irrigation for root zone moisture must usually wait until field activity ceases for a couple of days or more.

Proper water management, especially on high-traffic sports fields, require a constant vigil on weather forecasts and scheduled field activities.

Mowing

Since most cool-season turfgrass species prefer mowing heights greater than warm-season grasses the cutting units on mowers should be raised during the winter. The proper height depends on the cool-season species and variety however, a general rule-of-thumb is between one and two inches for most athletic fields. It's usually better to mow at the upper height within the range of high-traffic turfgrass to provide greater verdure, or healthy green color, and surface biomass in order to help protect the crown of the plant and provide more field resiliency.






Too much water can lead to root rot and may result in play tearing up fields. Too little can result in brown grass, poor footing and injury to players. Turf managers should note temperature, humidity, cloud cover and field use to custom tailor each day's irrigation.


Mowing frequently (2 to 3 times per week) helps to ensure the "1/3 rule" and help provide a dense surface canopy. The 1/3 rule refers to a mowing frequency that maintains no more than 1/3 of the total shoot (leaf) length being removed with any single mowing. Prudent fertility, proper irrigation and adequate drainage for healthy turfgrass growth usually require mowing more than once per week.

Fertility

Proper nutrition is essential for turfgrass to withstand the stresses and pressures of high traffic. Heavy usage of sports fields takes its toll on turfgrass. In order to have a fighting chance of survival and recovery it must be properly fed through a prudent fertility program.

The physical, chemical and biological properties of the root zone are important factors to consider when developing a comprehensive fertility program. Each factor has a direct correlation on the effectiveness of the nutrients reaching the plant.

The first step in establishing a fertility program is identifying the root zone properties through a soil analysis. A soil analysis, depending on how comprehensive it is, will reveal the effectiveness of the growing environment and what necessary actions should be taken to improve that environment. Some of the improvements involve enhancing drainage, lowering or raising soil pH and/or increasing the beneficial microbial population. A soil analysis will also provide the soil's nutritional status. It is suggested that a representative sample of each athletic field's root zone be sent to a reputable laboratory for a comprehensive analysis to determine existing soil properties.

Once the root zone composition is known then the next step is to determine the best method to get the nutrient into the plant.

Summary

Maintaining winter turfgrass on high-traffic sports fields in the southern regions of the country can be very challenging. Because winter temperatures allow for year-round field activity most athletic fields rarely enjoy any downtime for recovery.

Because of year-round use nearly all warm-season turfgrass sports fields are overseeded with cool-season grasses to support winter play. However, the challenges of establishing and maintaining a safe and playable surface during heavy activity can leave both the field manager and the grass exhausted.

Prudent cultural practices that focus on optimum soil moisture, proper mowing practices and prudent fertility that are effectively performed within and around the confines of heavy field activity can yield effective results. Keep in mind that year-round activity requires a year-round management plan.



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November 22, 2019, 1:09 pm PDT

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