How fast is too fast?

By Amber Friedrichsen

Engines are revving up as first-crop hay cutting approaches. Before stepping on the gas pedal, though, know the operating limits of mowing machines to ensure a successful harvest.

Disc mowers have largely displaced sickle bar mowers in the nation’s hayfields, with disc configurations allowing for faster ground speeds. However, if speed impacts the quality of cut, it might be time to pull back on the reins.

“A critical travel speed for mowing is defined as the maximum speed a machine can travel without leaning the crop forward as it passes and maintaining a clean cut of the crop,” says Brian Luck with the University of Wisconsin-Madison.

The extension agricultural engineer explains in a recent issue of the Midwest Forage Association’s Forage Focus that two factors of cutting productivity are width and speed. Width is fixed by design, so one way to improve productivity is to invest in wider equipment. Another option is to pick up the pace, but moving too quickly might leave stems with rough and ragged edges that can impair regrowth.

Luck notes the American Society for Agricultural and Biological Engineers Standard for Machinery Management Data gives an average mowing speed range for grass and alfalfa as 7 to 14 miles per hour with an average of 10.5, but he adds the data for this calculation is somewhat old.

In 2018, the world record for acres mowed in an eight-hour day documented an average mowing speed of 19 mph. Faster yet, Luck says some mowing machines are being tested at speeds over 25 mph.

Even though mowers have the capacity to reach high speeds, adverse field conditions can make farmers pump the brakes. Factors like field roughness, obstructions in the soil, and soil moisture should be navigated at a reduced pace.

“Rough fields can cause damage to the machine, so going slower would be recommended,” Luck advises. “Obstructions, such as rocks, tile holes, or foreign objects can also cause substantial damage to hay mowing machines.”

In addition to damaging machinery, operating in wet conditions can cause damage to a field. Tires can drag through the mud and machines are at risk of getting stuck when soil moisture is high. Trying to go faster in these conditions can be even more harmful.

Another thing to consider is high-yielding crops. Luck says dense grass might require mowers to move more slowly through them. Power availability of the tractor can also limit mowers in these situations.

Identifying challenges within a field and adjusting speed accordingly will help determine a proper mowing pace. Maximum productivity will only be achieved when a machine is working optimally and producing a quality cut.

“Ensuring a clean cut of the crop is a priority during harvest,” Luck asserts. “When operating this spring, be mindful of how your mower is performing and be sure you are within its operating limits when it comes to speed.”


Amber Friedrichsen

Amber Friedrichsen is serving as the 2021 Hay & Forage Grower editorial intern. She currently attends Iowa State University where she is majoring in agriculture and life sciences education-communications with a minor in agronomy. Friedrichsen grew up on her family’s diversified crop and livestock farm near Clinton, Iowa.