Maintaining bentgrass fairways in the southeast has always been a challenge during the hot and humid summer months of July and August. Bentgrass is a cool season turfgrass that prefers cool temperatures and moist soils. Bentgrass is an excellent selection for fairways, greens, and tees becuase of its fine leaf texture and its tolerance to low mowing heights. Kenmure Country Club is one of a very limited number of golf courses this far South that maintains bentgrass fairways. Having bentgrass fairways in this climate should be considered a luxury and something that we should all be proud of and try to protect. I am sure everyone is curious about all the brown and dead spots that are occuring around the golf course and I will do my best to explain what is currently happening. There is no single thing that causes the damage but rather a number of different factors that all add up to what we a currently experiencing.
Air and Soil Temperature
Bentgrass is not an extremely heat tolerant plant. Air and soil temperatures above 90 degrees destroys the root systems and stops all shoot growth. This leaves the plant unable to recover from any damages until the heat subsides and moderate temperatures return. During the last few weeks we have had soils temperatures between 94-98 degrees. The optimum soil temperature for bentgrass root growth is between 60-75 degrees, with 50% root loss occuring at 75-77 degrees, and growth limiting temperatures after 80 degrees.
Rainfall, Humidity, and Air Movement
During the month of July we were not able to control the amount of moisture in the soil. We recieved rainfall so many times in July we only had to run our irrigation system a few times. We applied the lowest amount of water to the golf course in July using the irrigation system then we have ever done in the past 5 years. The high humidity during the past month made it very difficult for the plant to cool itself off. The humidity combined with areas on the golf course that have little air movement also contributed greatly to the stress. Fairways like 16 and 17 are in sunken pockets that swelter in the stagnant air.
Disease Pressure
We invest 45% of our operating expenses into chemicals to control various turf diseases. This is an absolute neccesity with bentgrass. To make matters worse, the majority of our rough is also bentgrass which needs to be sprayed with regular frequency or it will suffer greatly. Heat, moisture, and humidity are the three major factors that influence turfgrass diseases. Treating 40 acres of bentgrass through this difficult time is a huge and very expensive challenge. During this summer period of high stress it becomes very difficult for the grass to recuperate when it becomes diseased. An ugly area of turgrass that would normally heal in a weeks time after being sprayed in the spring and fall will not bounce back at all in the summer period until the high temperatures subside.
Cultural Practices
The greens and tees are mowed lower, cut with more frequency, and are drier than the fairways. Why do they all look fine and some fairways look bad? The answer is simple, it is all due to the cultural practices we apply to the greens. This means spraying chemicals at a closer interval, aerifying and topdressing twice a year, and watering them mostly by hand. We apply these practices to the fairways, but in nowhere near the same volume. It is also very important to note that the greens and tees where constructed with river sand that gives them better drainage and an overall better growing medium for the plant.
Traffic Management
Soil compaction is a major factor in the healthy growth of bentgrass. Compaction is one the reasons it is very important to aerify in the spring and fall. Cart traffic causes a large amount of compaction and wear to the fairways. We attempt to manage traffic with signs and cart path only days. The effects of cart traffic generally go unnoticed in the spring and fall when the bentgrass plant is not stressed and growing normally. The combined wear from the entire year brings its heaviest toll during the summer months, in particular when we have days with air temperatures in the 90's. It becomes a very difficult situation because it is on these hot days when people need to drive to their ball the most.
Root Inhibition
A secondary factor that increases the difficulty of plant recuperation during summer stress periods is root growth inhibition from the chemical we use in the spring to control the crabgrass and goosegrass populations. These chemicals do not hurt the growth of any exisiting root structures, but do inhibit the growth of new roots in the areas that need to heal.
Final Thoughts
As you can now see there are many facets to understanding the underlying causes of brown turf. We experience brown areas of bentgrass during the hottest parts of the summer every year here at Kenmure. Most of these spots will heal on their own once we get into the fall, some will require seeding or sodding. 10 out 12 months we have a favorable climate to support healthy bentgrass, its is only a short window where we are at the mercy of mother nature. There is no single tailored solution or action plan to deal with these conditions as no two summers are alike and conditions can vary greatly from week to week or even from day to day. It would be wonderful to be able to go home from work at night and come back to the same golf course I had left the night before, but this is almost never the case during anytime of the year. Thank you for your continued support of the golf course and I hope you enjoy the rest of the season.
