Mowing is a primary cultural practice and a necessity for maintaining healthy and functioning turfgrass. In the past, lawns were kept at an acceptable height by grazing animals such as sheep and rabbits. Lawns were also mowed with a scythe, a hand-powered tool borrowed from a device used to cut and harvest wheat. In 1830, Edwin Budding invented the first mechanical mower, the template for today’s reel mower. Horse-drawn reel mowers and small, human-powered push reel mowers represented the latest mowing practices back then.
The shift to reel mowers allowed turf to be cut lower to produce a more desirable playing surface. The first gasoline-powered reel mowers were introduced in the early 1900s. Gang mowers with multiple reel units pulled by tractors appeared in the 1920s. Zero-turn mowers were introduced in the 1950s. In the 1970s, hydraulics improved these machines, and large-scale riding reel mowers become common.
Today, rotary and reel mower machines continue to improve and are lightweight compared to their forefathers. Robotic or autonomous technology represents the next evolutionary step with mowers. Therefore, research was conducted during two consecutive years at the Norwegian Institute of Bioeconomy Research (Grimstad, Norway) to evaluate different cool-season turf species in response to autonomous mowing on golf course fairways.
In the first study, three large test plots consisted of a single pure turf species: red fescue (Festuca rubra), Kentucky bluegrass (Poa pratensis) or colonial bentgrass (Agrostis capillaris). Lightweight autonomous mowers (Husqvarna Model 550; Husqvarna Corp.) were programmed to mow one set of plots from 8 a.m. to noon every day, and another set of plots was mowed in the early morning with a triplex reel mower on Monday, Wednesday and Friday. With both mower types, the fairway height-of-cut was set at 0.590 inch (1.5 centimeters). All test plots received granular fertilizer with an annual nitrogen (N) amount of 1.2 pounds nitrogen per 1,000 square feet (60 kilograms N per hectare) and subjected to simulated traffic to resemble the wear common to fairways. White clover (Trifolium repens) plants were plugged into all test plots to determine if mowing had an influence on this weed.
Overall, visual quality was acceptable for all three turf species maintained with either the autonomous mower or reel mower. With all three turf species, visual quality ratings were higher during the summer and fall in autonomous-mowed plots compared to reel-mowed plots. The researchers concluded that switching from reel mowing to autonomous mowing resulted in no risk of decreasing fairway turf quality. Also, the better quality in autonomous-mowed turf could be attributed to more frequent dew removal, which means reduced leaf wetness and therefore an unfavorable microenvironment for foliar diseases. With both autonomous and reel mowers, white clover did not significantly expand into the test plots at that fairway height-of-cut and frequency.
In a second study, test plots of a mix species (50% red fescue, 45% Kentucky bluegrass and 5% colonial bentgrass) received the same mowing parameters as the first study. Sub-plots received granular fertilizer at an annual rate of 0, 0.6, 1.2, 1.8, or 2.4 pounds N per 1,000 square feet (0, 30, 60, 90 and 120 kilograms N per hectare). Higher turfgrass quality was observed with autonomous mowing regardless of N rate. However, N applied at ≥ 1.2 pounds N per 1,000 square feet for both mowers was needed to maintain the competitive advantage of turf over white clover infestation.
Over time, the botanical composition of the turf was examined. Autonomous or reel mowers had no effect on the number of tillers of red fescue, Kentucky bluegrass or colonial bentgrass. Therefore, the frequent mowing from the autonomous mower did not facilitate a shift in species composition.
Today, autonomous mowers must operate nearly every day to maintain the desired mowing height and playing surface for fairways, as compared to mowing three days per week with a human-operated reel mower. These autonomous mowers typically utilize two-sided blades mounted on a circular, horizontally rotating head. In the future, perhaps improvements to lightweight, battery-powered autonomous mowers may include an improvement on traditional reel blades. Robotic or autonomous technology represents a great opportunity for the next generation in the turfgrass industry.
Source: Hesselsøe, K.J., A.F. Borchert, T. Pettersen and T.S. Aamlid. 2025. Transitioning from traditional to robotic mower affects turfgrass quality and broadleaf weeds on golf course fairways. International Turfgrass Research Society Journal 15:109-120.
Mike Fidanza, Ph.D., is a professor of plant and soil science in the Division of Science, Berks Campus, at Pennsylvania State University in Reading, Pa. He is a 24-year member of GCSAA.