For anyone who watched major college football in the Midwest this fall, you’ve noticed that the fields are tearing up with divots and blow outs. Some major universities have even resodded their fields after the opening few games in hopes of improving traction. In a nutshell, this is why fields are tearing up:
- Root growth of cool-season grasses reaches a peak in mid-spring and declines with summer, basically stopping once soil temperatures reach 70F.
With increasing soil temperatures, root growth does not keep pace with root dieback, thus root systems naturally become shallower and lose density during the heat of summer.
In the West Lafayette, we’ve had 65 days of temperatures 85F or greater this summer, 22 of which were over 90F including a number in September. Thus soil temperatures were still in the high 70’s or low 80’s throughout much of September.
The root growth is further compromised by reduced photosynthesis and increased respiration at the elevated temperatures, thus there is barely enough energy production within the plant to keep it alive, much less grow roots.
We normally expect a small flush of root growth (and top growth) starting in September and continuing until November, but high soil temperatures have delayed this flush.
At most major universities, sand-based fields are used to maximize drainage and avoid the “mud” games that were common in the past. Unfortunately, sand does not have the inherent shear resistance like soil-based fields and divoting becomes a major problem after summers like this.
Now that air and soil temperatures are finally lowering, root growth should resume and footing should gradually improve. Aggressive fall nitrogen using mostly fast release sources applied at 0.5-1.0 lb N/1000 sq ft every 2 to 3 weeks will help rooting and increase lateral spread of the turf. Overseeding perennial ryegrass should also be used to improve aesthetics and footing in the short-term, but unfortunately cooler temperatures may slow or even prevent germination and establishment. The best case scenario is that we have warm, sunny days in the 70’s well into late Oct. and Nov which will allow for quick germination, maximum top growth, good lateral spread, and good root growth. The worst-case scenario is a short, cool fall which would result in continued poor traction and severe turf damage.