To roll or not to roll... why is that a question?

For about 50 years, greens on U.S. golf courses were mowed at the same height of cut. Then something came along to change everything, to the chagrin of superintendents everywhere.

In Tuesday’s “To Roll or Not to Roll,” session, part of the 2013 GCSAA Education Conference in San Diego, attendees heard from five speakers about research that’s been done to tell us precisely how frequently and when to roll for the best results, as well as what other cultural practices can affect green speeds. On the panel were Rob Golembiewski, Ph.D. at Bayer Green Solutions; Paul Giordano, graduate assistant at Michigan State; Doug Karcher, Ph.D. at the University of Arkansas; John Sorochan, Ph.D. at the University of Tennessee; and Thom Nikolai, Ph.D. at Michigan State.

Golembiewski, who previously worked at Oregon State University before going to Bayer, put the demands of contemporary green speeds into historical perspective. In 1928, mowers were set at 3/8 inch, or 0.188 inches. That remained the status quo for about 50 years. Then the Stimpmeter came out and changed all that. In 1976 and 1977, Golembiewski said, the average green speed across the country was 6’6”, and anything over 7’6” was considered “excitingly fast” by USGA Green Section agronomists.

Today, daily play green speeds range from 9 to 11 feet, and tournament speeds can exceed 13 feet.

“How far do you want to keep pushing it?” Golembiewski asked.

As we’re lowering and lowering mowing heights, root systems are suffering and the turf is getting weaker. Golembiewski pointed to research that showed that lowering the height of cut by 1/32 of an inch resulted in a 30 to 40 percent reduction in photosynthesis. Lower mowing heights can also result in more moss, increase in disease occurrence and increased susceptibility to stress.

Luckily, much research has been done on how rolling can affect green speeds and solve some of these issues. “If all you’re doing is mowing, I recommend rolling,” he said. “It can slightly increase green speeds, and overall health is much improved.”

Giordano’s portion focused on the effect of frequent lightweight rolling on dollar spot – specifically, that it decreases dollar spot occurrence. Why? Rolling removes dew, removes leaf litter, decreases the concentration of guttation, increases soil moisture holding capacity, and induces plant defense responses. He conducted research that sought the results of rolling twice per day – would it double the disease reduction?  A couple of hypotheses resulted – but both point to decreased incidence of dollar spot with rolling twice a day.

Other research presented by Karcher and Sorochan looked at results of rolling up to 8 times a day, and alternating mowing with rolling.

Karcher said that by rolling once a day, they gained more than a foot in green speed, but there wasn’t much difference between rolling once a day versus eight times a day.

Sorochan proposed the economic benefits of alternating mowing with rolling. Private clubs saved up to $22,000 a year in one study he cited. Alternating rolling with mowing can also improve turf quality, particularly during periods of heat stress, he said. Despite all the research already done on the subject, “We need to do more rolling and mowing research,” he added.

Finally, Nikolai revealed the results of a study he completed with GCSAA’s help – it asked superintendents to list the 10 changes that have improved the game of golf over the last 25 years. Lightweight rolling was third on the list. He questioned what, if any, negatives there are to rolling, given the abundance of benefits. It remains to be seen, but he commended all the research done to further our understanding of the impact of rolling.

Of the top 10 improvements superintendents listed in his survey, “research had to do with 9 out of 10 of those.”