As we see our 5th day in a row with temperatures exceeding 90 degrees, there is little doubt that summer is upon us. We all know that the summer months can be challenging for cool season turfgrass. We would like to explain some of those challenges and discuss our strategies for providing the best possible conditions... despite the heat and humidity of July and August.
Before we discuss the summer season, we are pleased to say that the golf course is in a strong position coming out of a very successful spring. Our bent grass surfaces continue to be dense and firm, while our rough remains thick and consistent. Our newly installed rough (over 35 acres of Fescue) is settling in well. Furthermore, we see very little Bermuda grass and the Bermuda we do see is not returning in the areas that were eradicated last summer.
So, what makes the summer months difficult for cool season grass? And more importantly, what do we do to ensure healthy playing surfaces throughout the hottest times of the year? The answers to these questions can be found below. In this update, we have outlined the specific challenges and after a brief description, we discuss the strategies that are employed to combat these challenges. We hope this information is useful and as always, feel free to reach out with specific questions or concerns.
- 1. Mechanical Stress
Problem – Rollers, mowers, sprayers, tractors and golf carts. All great pieces of equipment for operating and maintaining a golf course. But, when the plant is under duress, all this machinery adds extra wear to the grass plant.
Strategy – When we walk mow our greens, tees and approaches, the operators walk in straight lines. At the end of each pass (line), they must turn the mower to make their next pass (line). This 180-degree turning puts a lot of pressure on the “edges” of our surfaces. To mitigate this stress, we use lighter mowers and turning boards. A turning board is a 3’ x 4’ piece of light plastic that the operator places on each side of the surface. As the mower makes its turns, the turns stay on these sheets of plastic, thus reducing the mechanical stress. In addition to turning boards, we use gentle, smooth front rollers, ask our bunker staff to walk from the path and ask that our rough units return to the shop by 11:00 AM to avoid midday heat. All these things are done daily to reduce as much mechanical stress as possible.
- 2. Humidity and Transpirational Cooling
Problem -Cool season grass plants thrive in temperatures that range between 60- and 80-degrees Fahrenheit. Once daytime temperatures exceed 85 degrees, the grass plant begins to overheat. Like
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humans, grass plants regulate their internal temperature by sweating. But in turf parlance, we call it transpirational cooling. The plant moves water from its rootzone, through its Xylem cells, upward to the leaf. Once near the canopy, the plant releases microscopic water droplets through tiny openings in the leaves called stomates. This water evaporates, expending heat energy, thus lowering the temperature of the plant. Unfortunately, with summer heat, comes summer humidity. This humidity saturates the air above the plant and does not allow the water released through the stomates to evaporate. This stymie effect results in a grass plant being unable to cool itself through transpiration. Like humans, if grass overheats long enough, cell functionality suffers and the plant dies.
Strategy – This problem sparked the usage of oscillating fans. Fans are designed to constantly move the air above the grass plant so that humidity-based saturation cannot occur. If the air is not saturated, evaporation can occur, and the plant can cool itself. Therefore, you always see fans in “pocketed” micro-climates. Stagnant air is often wet air. In addition to fans, you may see our team lightly syringing the grass. This process is unlike hand-watering as we are not trying to add soil moisture, but temporarily cool the plant, while adding moisture to the leaves for evaporation.
- 3. Scald
Problem – Scald occurs when saturated soils heat to the extent that it literally “cooks” the grass. Water is denser than air so a wet rootzone can retain much more heat than a dry rootzone. Sometimes in the summer, if we receive a heavy downpour that is followed by high temperatures, we will see grass killed in lower areas that remain saturated. Scald is also why we are very careful not to over-irrigate the golf course.
Strategy – This specific problem is difficult, because it often occurs at the whim of Mother Nature. We cannot control a 2” rain event, followed by 95 degrees with high humidity. But we can be cognizant of the problem and proactively install drainage, spray a bi-weekly or monthly wetting agent and vent on a regular basis. We do all these things throughout the summer. Also, reducing opportunities for scald is another benefit of our topdressing program. As we continue to develop more permeable surfaces, less water can saturate the crown (brains) areas of our grass plants.
- 4. Wilt/Drought
Problem – When soil moisture becomes critically low, the grass plant does not have enough water to function. Once the plant has endured enough dehydration, it loses turgor pressure and cells begin to die. I’d also say that wilt is one of the biggest reasons why we like to reduce cart traffic in the summer. When plant cells are suffering from wilt stress, there is not enough moisture to keep those cells pliable. So, when the plant is compressed, instead of “bouncing back”, the water deprived cells break and die. This phenomenon is eerily like frost damage and that is why cart tracks through wilt turn dark blue/black.
Strategy – As soil moisture is lost through plant usage and evaporation, it is our job to replace that moisture. Although we have an excellent irrigation system, with over 2000 sprinkler heads, we cannot saturate the soil, night after night. Aside from the massive detriments to playability, this strategy would induce a laundry list of problems such as scald, algae, increased disease pressure and anaerobic root zones. Thus, we water at night to the bare minimum that the plant needs to thrive the next day. As drier areas are identified, we use water hoses to surgically apply water to those specific areas.
- 5. Pests – Disease and Insects
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Problem – Pythium, Brown Patch, White Grubs, Weevils... or known as enemies of turf. The previously mentioned combination of disease and insects are just a few pests that we must battle throughout the season.
Strategy – We believe in an Integrated Pest Management system. In other words, we do not simply apply pesticides and call it a day. We scout for diseases and insects. We read blogs and talk to fellow golf courses to hear what they are seeing. We minimize excessive moisture, remove dew and follow strategic fertility plans. We do all these things in conjunction with a thoughtful chemical program that is laid out each off season.
- 6. Respiration versus Photosynthesis
Problem – We tried to save the best for last! When you see a beautiful lawn, shrub or shade tree, what is the first word that should come to mind? Carbon! Carbon is the basis for life, and it is no different for a grass plant. Everything about a grass plant starts with a carbohydrate (Carbon + H2O). Carbohydrates are constructed by combining sunlight, carbon dioxide and water. We know this process by the name photosynthesis, and it is the most important function for a grass plants success. Unfortunately, cool season grasses (C3), unlike warm season grasses (C4), cannot fix carbon with much efficiency during the summer months. Specifically, when C3 grasses do have access to abundant sunshine, it is also hot. Thus, the plant begins the process of respiration more than the process of photosynthesis. Respiration occurs when the plant breaks down carbohydrates for growth functions. So, now we have grasses that are spending more energy than they are making. This imbalance is analogous to a human expending more calories than they take in. For a while that is called weight loss, but at a certain point, that imbalance will become unhealthy.
Strategy – We cannot stop the summertime imbalance between photosynthesis (energy creation) and respiration (energy consumption). So, we must “bank” as many carbohydrates as possible during the spring season. To do this we feed the grass a balanced diet of nutrients as prescribed through soil and tissue testing. We also work to increase rooting through extensive aerations and top dressings. Remember, the more rooting, the more energy that can be “banked”. We also promote general plant health through timely mowing, sharp cutting units, traffic mitigation and the like. Essentially, our job in the spring is to produce firm, fast and aesthetically pleasing conditions, all the while preparing the turf for the inevitable energy short falls brought on by summer. This balancing act is what makes turfgrass management so much fun!
We hope that this report helps you to understand what we do to manage the playing surfaces at Kinloch Golf Club. We are truly blessed to take care of such a great course and are ever grateful for the support of our General Manager, Board of Directors and You, our member. Enjoy the golf and stay safe!!
