By Barry Stewart, Ph.D.
The COVID-19 crisis has had a profound effect on many athletic fields in Mississippi and throughout the southeast. When the lockdowns and social distancing began, high schools were getting into the heart of their softball and baseball seasons and some were starting to prepare for spring football. Our park and rec fields were coming out of dormancy. Hopefully, most had gotten their spring pre-emergence herbicide treatments down, but I am sure that some had not. Overseeded fields were just starting to really grow as the weather warmed a bit. Now we have many different situations out there. Some institutions were able to not miss a beat in their field management routines and their fields look like they could host a tournament tomorrow. On other fields, the gates were locked mid-March and they have not been maintained since. The question is how we get the fields that were neglected ready for play.
For us, the timing of the COVID-19 crisis was somewhat fortuitous in that it came in a period in which our temperatures were below normal with cool nights. This slowed the growth of our bermudagrass. Unfortunately, this has also been a good growth period for any cool-season weeds that were in our fields, and this has been a very good year for Poa annuaand other cool-season weeds. On many weedy fields these weeds have held back the bermudagrass, and it may not even be fully greened up – although it is getting close. These are very competitive weeds, but their lifecycle is winding down. It is too late to control them with herbicides. The best tool to control them is a mower. On many fields the bermudagrass is not over 1 inch high and the weeds are much higher, so in our first mowing we will mostly be mowing weeds. For that reason, field managers may want to mow once or twice with a rotary mower and collect the clippings before getting out the reel mower. The vacuum action of a rotary deck may also suck up some of the senescent leaves from last year’s grass as well. Once you can get out the reel mower, I would try to get to my intended mowing height as quickly as I could. Most of the places I have seen will not have a lot of scalping – the bermudagrass is not growing fast yet. If you have access to a turf sweeper, it would be a very good time to use it.
Once we get to our intended cutting height, follow the 1/3 rule to determine when to mow – not a calendar-based schedule. If we are mowing at 1/2 inch, this means mow when the grass reaches 3/4 inch, or if we are mowing at 1 inch, mow when we hit 1.5 inches. This might be a time to contemplate moving your mowing height up a little with the uncertainty of the coming season. If your normal mowing height is a 1/2 inch, consider 5/8 inch; if your normal mowing height is 3/4 inch, consider 7/8 inch; or if you are at 1 inch, perhaps 1-1/4. These higher mowing heights might allow you save on some mowing but still have you near your usual height of cut. The increased mowing height may actually slow the growth of the grass a bit. Research done at the University of Wisconsin found that grass at greens height grew 40 percent faster than grass at collar height, so it stands to reason that increasing our mowing heights could decrease our growth rates. Only if there is a paucity of manpower and/or funds, consider mowing heights of over 1.5 inches for bermudagrass fields. As our mowing heights creep above 1.5 inches our traffic tolerance decreases.
If the budget allows, this is an excellent time to apply plant growth regulators (PGRs). Applying a product like trinexapac-ethyl will cut our mowing by about 50 percent, and make scalping less likely if we miss a mowing due to wetness or lack of manpower. The savings in mowing normally cover the cost of the PGRs.
If you have not had a soil test for a couple of years, now is the time. If you have a current soil test, follow the recommendation for lime, P and K application. Fields that were walked away from in mid-March or the first of April probably had not been fertilized yet. Once we begin to mow we should also commit to fertility. For fields that are being maintained, following the 1/3 rule ½- to ¾-lb. of N per 1,000 ft2 month is recommended, and this should be upped to 1 lb. once the field starts to receive traffic. A fertilizer that is half quick-release N and half controlled-release N would be preferred. If a full-scale mowing program cannot be committed to (mow at an acceptable height of cut following the 1/3 rule) then a full fertility program should not be started. If a field is only being mowed high every couple weeks, then only about 1/4 to 1/3 lbs. of N per 1,000 ft2 per month is recommended. This will give the bermudarass a fighting chance to fend off weeds while not promoting too much growth.
Hopefully, most field managers were able to get their spring pre-emergence herbicide applications out on time, which would have been prior to mid-March. Some fields may not have received these treatments, and it is not too late to apply them. You have missed the initial flush of crabgrass and goosegrass germination, but that flush may have been delayed by competition from un-mown cool-season weeds. If there has been emergency of crabgrass, goosegrass and other warm-season weeds, applying a post-emergence herbicide when the weeds are young is most effective. A tank mix of a pre-emergence herbicide and a post-emergence herbicide would be a very timely application.
If heavy weed pressure developed during the time the field was not maintained, it is likely that a seedbank of winter weeds developed. With that in mind, a fall pre-emergence herbicide application will be very important. This application should be made as soil temperatures fall below 70 degrees Fahrenheit.
With no play scheduled for the fields, once we get our mowing under control and our fertility program started, it would be an excellent time for aerification, vertical mowing, and topdressing if manpower and budget allow. This would also be an excellent time to apply lime, P and K if needed. This is an opportunity to do many of the cultural practices that often are neglected because of busy schedules. This would be a fantastic time to fraze mow fields, but it is a manpower-intensive practice and may not be practical at this time.
The longer maintenance is delayed, the more the bermudagrass is going to grow. As it grows without mowing pressure it will grow vertically seeking more sunlight, and turf density will decrease, allowing weeds to get a foothold and making getting back to normal conditions more difficult. Fields that are not maintained until August may be thin and not safe for fall play. These thin fields may also not have as much traffic tolerance and may not hold up to the wear and tear of normal use. The hard work that has made many outstanding athletic fields can be undone in one summer.
Barry Stewart, Ph.D., is associate professor at Mississippi State University. He teaches courses in Athletic Field Management, Golf Course Operations, and Plant Science. His current research focuses on athletic field quality and sustainable turfgrass management. He is a part owner of the Green Bay Packers.