Athletic field managers work hard to maintain quality and highly playable fields throughout the year, but summer maintenance for cool season sports turf managers offer a specific and demanding set of challenges. Keep an eye out to fall maintenance as well. High heat, excessive dry or wet conditions, and traffic all lead to a high potential for a loss in turfgrass vigor, recovery, and growth. Consider doing less, not more, to effectively manage challenging situations and remember to take advantage of what you can control. This includes decisions about irrigation schedule, selection and timing of crop protectant application, nozzle selection, equipment calibration, aeration and nutrient application timing, and seeding rate and timing. Think about agronomic basics that promote optimum vigor and plant recovery including height of cut, fertilization, and crop protection and water management. Let’s start with a more in depth discussion about vigor, growth and playability and keep you moving forward to keep turf growing aggressively for the rest of the season!
Turf managers must become keen observers to determine levels turf vigor. Consider the definition of vigor: physical strength, energy or force; capacity for natural growth and survival. Ask questions while you observe, for example, how do plants recover from environmental or mechanical stress? How do plants respond to fertilizer applications? How do plants respond to or compete with pests? Turf management on a very basic level centers on competition. Creating a scenario where the desired plant has a competitive edge, right? That’s it in a nutshell. Add in traffic and the situation changes again making the job even more challenging. An enhanced base level of vigor means more opportunities for better playability, the ultimate goal. With increased vigor, you can control and fine tune other factors more aggressively such as height of cut and water management to further ‘fine-tune’ playability. Maximizing plant vigor offers a buffer. How do we maintain it for cool season grasses in the summer?
Choose the correct source, dose and timing for nutrient applications for the rest of this summer and fall. Spoon-feed with an efficient foliar and soluble nutrient source, particularly nitrogen (N). This approach offers control of shoot growth, promotes rooting, and ensures the supply of adequate nutrition when environmental factors including soil physical properties (temperature/water status) may limit growth. Roots are key to getting through the growing season and N plays an important role. When seeding, foliar nutrition promotes faster establishment after germination. In the fall, apply higher doses of N and utilize more granule formulations. Consider granule formulations with at least 50% slow release nitrogen; this approach provides metered N release throughout the fall when N demands are high. Look for balanced formulations or tank mixes, particularly the liquid/foliar formulations that offer compatibility with crop protectants.
Use history as a guide. Do not make pesticide applications based on a calendar date and always read the label before applying. Develop a integrated pest management (IPM) program by utilizing all options, focus on scouting and mapping, develop tolerance levels, and consider the safety to applicators, non-target organisms and the environment. Triple rinse all application tanks and equipment to ensure cleanliness, keep accurate records and store pesticides in a clean, dry and dark location. Since pre-emergent herbicides have likely been applied, focus now on post emergent weed control, particularly in high wear areas. Hold off on any herbicide application until the seeds have germinated and seedlings have reached the 3-5-tiller stage unless otherwise stated the label. Some herbicides are safe to apply prior to, or during, seeding.
Understand key timings and indicators for disease and insect pests. At this time of year, consider the management of late summer and fall diseases including pythium blight, brown patch, summer patch, and gray leaf spot. For insect pest pests, turn your attention to the control of sod webworm, white grubs, and chinch bugs.
Additional factors to consider:
- Correct pest identification
- Nutrient/pest interactions
- Pesticide target (soil or foliar)
- Rotating chemistries (contact v. systemic) to manage pest resistance
- Turfgrass species and cultivar selection
- Thatch and organic matter management
Select the correct nozzles (water droplet size), pressure, and water volume carrier. Select these factors based on target pest, coverage required, drift reduction, and tank mix partners. Generally, flooding nozzles work best at lower pressure and higher water carrier. Contact fungicides require adequate coverage that is best achieved with nozzles that produce a finer droplet size. It’s worth noting that the last piece of equipment the spray solution touches before the turf canopy and soil are the nozzles, so play close attention to those decisions. Remember to focus on factors in your control. Maintain turf vigor through sound cultural practices. Plant resistant cultivars and enhance soil microbial activity to most effectively reduce pest pressure without crop protectants.
Seeding, traffic and cultivation
Focus on high wear areas for seeding. Attempt to create a seedbed through cultivation and topdressing and roll for adequate seed/soil contact, if possible. Time the seeding immediately after games/events and as long as possible before the next event. Mid/late August represents the best timing for cool season turfgrass establishment. Avoid pesticides or high doses of soluble N in high heat where seedlings are immature as plant injury can occur.
To manage traffic, rotate field use were possible. Cultivate, groom, and topdress high use areas to reduce compaction and increase shear strength. Avoid aggressive cultivation during environmental stress. Focus on thatch reduction and aeration in the fall, which typically should occur in conjunction with inter-seeding or establishment of larger areas.
During environmental and/or traffic stress or low metabolic functioning, it’s best to raise the height of cut. The greater leaf surface area affords the plants increased light capture and photosynthetic activity. A higher mowing height also protects turf crowns, and promotes deeper roots. Based on your management strategies and observation, when plant vigor is high, you can lower the height of height of cut to improve playability, for example ball roll and speed, bounce consistency, player traction, and player running speed. In addition, a relatively lower height of cut promotes tillering, thus uniformity and shoot density. Always keep mowing heights within the recommended range based on breeder and National Turfgrass Evaluation Program (NTEP) evaluations and never lower the height of cut by more than one third. And finally, an effective turf manager must also correctly manage thatch before lowering the height of cut to avoid scalping.
Having access to an irrigation system makes it possible to control water inputs. When inputs are in your control and turf vigor remains high due to the other successful management strategies implemented, a valuable opportunity arises: to keep the surface dry using a deep and infrequent irrigation approach. Too much water at the surface of a sports field will limit rooting and gas exchange, leading to a handful of problems. Managing turf on a deficit irrigation schedule keeps soil moisture above the wilting point, but below field capacity. There are various ways to determine when and how much water to apply such as basing it on evapotranspiration loss or soil volumetric water content. Water deficit management will encourage plant acclimation to drought, build plant strength and improve rooting. In addition, you can expect better playability parameters such as reduced divoting, improved traction, and a ‘faster’ field surface.
Keeping the turfgrass growing during the season requires an integrated approach. Every situation is different including site, grass type, rootzone properties, resources, level of traffic, number of fields, etc. but one thing remains the same—a focus on the basics and what you control, plus keen observation, will provide the best chance for success. This includes nutrient management, pest control, and cultivation with an emphasis on building turf vigor, making it competitive! Keen observation allows you to determine what might me limiting or cause a loss of vigor and then correct the problem with the appropriate input(s). And with a solid base for vigor in place and when the timing is right, manage more aggressively for playability, the ultimate objective.
Gordon Kauffman III, PhD, is turf and ornamental technical manager for Brandt Consolidated.