Several superintendents in the Boston area have detected anaerobic or anoxic conditions under covers in the past week. This was a surprise, considering the limited snow and short duration of ice cover this winter. The presence of the all- too-familiar sweet and sickly smell is an indication that oxygen levels in the soil and turf canopy are dangerously low, and, in a worst case scenario, turf damage already has occurred.
Work in Quebec and at the Prairie Turfgrass Research Centre in Alberta has shown that annual bluegrass growing in anoxic conditions for 45 days begins to lose its tolerance to cold temperature. It is thought that plants undergoing anaerobic respiration deplete carbohydrate reserves more quickly, and thus cannot prevent freeze injury when exposed to colder temperatures. Did this actually occur on New England golf courses this winter? It is too early to say; however, an indication of anaerobic conditions probably means that the turf has lost some hardiness or, worse, has already been damaged, which may be the case at some golf courses.
The following actions should be considered as we enter the final stretch of the winter season.
- Begin checking under covers and ice layers for the presence of anaerobic conditions, and pull turf plugs if there are concerns about potential damage.
- Make plans to lift or vent under impermeable covers if a smell is detected. With no smell, there’s no problem at this point.
- Begin to monitor temperatures under impermeable cover systems, as snow cover is lost and the sun’s strength increases. Start the process of removing the impermeable covers once temperatures beneath the covers reach the 41°F-43°F range consistently. Plant hardiness declines rapidly at those temperatures. Use a permeable cover to protect the exposed turf while it re-acclimates to the new environment.
- Initiate the process to remove ice sheets if an anaerobic condition is detected at the surface of annual bluegrass greens. The recent rains and warmer temperatures in the forecast may offer a window to do so for some, while the wet, heavy snows will make that more difficult further north and west. There is always a risk associated with that action, but, in my opinion, there are few options if the anaerobic condition is detected. Use a permeable cover or blow snow back over the recently cleared surfaces to protect the exposed turf, if necessary.
Winter injury is a very complex event, controlled by many variables that are a long way from being understood. The techniques that are used to protect the turf are improving, but are not, and probably never will be, perfect. The best we can do is to try to identify the specific causes of injury and then address as many of those factors as possible with the available management options. This reconfirms why it is a good idea to periodically pull grass plugs throughout the winter, especially following weather events when the turf may have been hydrated and then subjected to very cold temperatures.
Ah, winter in the Northeast. It’s never predictable and always interesting…
These topics and more will be covered at the New England Regional Turfgrass Conference in Providence, RI March 1-4. The USGA Session will be held on Tuesday March 2nd with a wide range of agronomic and golf related topics. We hope to see many of you there.