Q & A WITH DR. GRADY MILLER

I was asked earlier this week if it was time to begin core aerification of sports fields. Earlier in the year, I received more than a dozen questions asking when to initiate pre-emergence herbicide applications. These are just two examples of decisions made in sports field management that may be time sensitive.

I know many of you, like me, keep detailed work calendars for scheduling and recording daily tasks. As part of research project protocols, I need to schedule treatments and data collection reminders in my calendar weeks, months and / or years in advance. If we have inclement weather on the scheduled dates, adjustments have to be made. As a sports field manager, you have to schedule work around events, practices and inclement weather. If you are like me, you do not like changing your schedule, because moving one activity is likely to cause a domino effect that requires moving other activities to different dates.

Climate, which is usually defined as long-term weather trends, has become a scheduling influencer in recent years. It has required us to move up some activities and delay others. If you have always set management practices to specific dates months or years in advance, using climate indicators for scheduling may be a bit disconcerting to you.

The first core aerification each year is a practice that should be based on climatic conditions. The standard recommendation is that aeration of warm-season grasses should take place when the grass is actively growing. For the transition zone of the United States, the active growing season usually kicks off late April to early May( and typically earlier in more southern locations). If the turfgrass is actively growing, roots will quickly begin to grow in open holes from the aeration, and cavitation of soil will begin to fill the void. With healthy turfgrass, lateral stems will quickly cover the surface opening.

Open aerification holes in the spring may promote more soil warming since air is more easily heated than soil. This can be good or bad. If there is early green up and a late freeze, it can increase freeze damage since it results in a more rapid drop in the soil profile’ s temperature and a greater chance of turfgrass desiccation. For this reason, a predetermined date to aerate without considering the last frost date for the region is not recommended.

The application timing of herbicides has an even greater dependence on climatic conditions. Pre-emergence herbicides need to be applied before the weeds emerge. Research data indicates that crabgrass can begin to emerge when the soil temperature reaches approximately 55 degrees near the soil surface for three to five days. Over the last five years in North Carolina, this has required the first herbicide application to be two to four weeks earlier than our traditional recommendations.

The take-home message is that sticking to previously used calendar dates for some practices may not be effective, or it might even have negative consequences. Responses we experience in a turfgrass system are more heavily related to temperature or other biological events than a date on a calendar. The good news is that it’ s never been easier to track air and soil temperatures.

And although one can take these temperatures on site, it is usually better to use a government-based or online commercial resource for weather tracking, as they often report rolling averages. Disease prediction using daily average air temperature and relative humidity has also become very effective, and allows turfgrass managers to effectively time preventative fungicide applications.

Author’ s note: Some resources we use to predict weeds and disease include the National Centers for Environmental Information, GreenCast by Syngenta, and our state climate office.

Grady Miller, Ph. D. Professor and Extension Turf Specialist North Carolina State University

Questions? Send them to Grady Miller at North Carolina State University, Box 7620, Raleigh, NC 27695 or e-mail grady _ miller @ ncsu. edu

Or, send your question to Pamela Sherratt at 202 Kottman Hall, 2001 Coffey Road, Columbus, OH 43210 or sherratt. 1 @ osu. edu

50 SportsField Management | May 2025 sportsfieldmanagementonline. com