Fall Coring

With fall approaching, coring becomes the prevalent practice on many golf courses.  Fall coring relieves soil compaction, reduces thatch and organic matter levels, increases soil aeration, and stimulates new growth.  The desired window for fall coring is around Labor Day, but golf courses can schedule the practice as early as mid-August through October.  Early September is the desired time because air temperatures are beginning to moderate, but soil temperatures remain warm enough to promote turfgrass growth and recovery from summer stress.  In addition, temperatures at the time promote turf recovery from the mechanical activities associated with coring.   

Deviations from the desired time add a degree of risk to coring.  Early-August coring may occur during summer stress periods.  Soil temperatures may be high, limiting root growth.  Thus coring may slow root recovery through mechanical injury.  Close monitoring of evapotranspiration rates, and soil moisture is critical.  Rapid drying of the turf can occur, resulting in drought stressed turf.  Leaving sand from heavy topdressing for a short duration can cause a rapid increase in canopy temperature injuring the turf.  Conversely, when you wait until late in the fall, turfgrass slows and recovery from coring is prolonged or delayed.

Schedule fall coring well in advance so that golf club members and golfers are aware.  The least liked agronomic practice of golfers is coring.  It is disruptive, often closing the course for a few days and course recovery is often 2 to 3 weeks before returning to the desired firmness, smoothness and speed.  Here are a few key points for enhancing core recovery and returning the turf, especially greens, to their desired level.

1. Time – As mentioned previously, coring in the northern United States is targeted around Labor Day.  However, there is no guarantee that temperatures will be ideal.  For cool-season turfgrasses target coring when soil temperatures are below 70 °F, ideally in the 60 to 65 °F range.
2. Clean sharp core holes - A clean core cut results in the core hole recovering quicker.  The analogy would be cutting turf with a dull blade versus a sharp blade.  A dull blade results in tearing or fraying action that requires the plant to spend more energy and time repairing itself than a sharp cut.
3. Sand Topdress – When topdressing to fill the core holes use a dry sand and apply to a relatively dry turf surface.  Dry sand readily infiltrates down into the turf.  It is easily moved into the holes by brushing, brooming or dragging.
4. Roll Greens – After coring and topdressing roll the greens.  This will smooth the green helping reduce any minor deformities caused by coring. 
5. Irrigate and Fertilize – Irrigate to prevent moisture stress and promote growth.  Late summer through early fall is an ideal time to fertilize to promote turf recovery. 

About the author

Dr. Karl Danneberger is a professor of Turfgrass Science at The Ohio State University. Dr. Danneberger's contact information can be found here. You may also follow Dr. Danneberger on Twitter: @GlobalTurf