A University of Wisconsin ag engineer has confirmed what growers investigating wide swaths already know: Few mower conditioners or windrowers on the market today can cut a wide enough swath.

Forage cut in wide swaths — over 80% of the machine's cutting width — can dry to 67% moisture within eight hours, according to one study done on the subject. Narrow-swath forage, in comparison, took 24 hours to dry to 77% moisture. Forage spread in wide swaths also suffers fewer respiration losses.

In first-cutting alfalfa, wide-swath haylage could increase milk production by 20% over haylage chopped from narrow swaths. For second-cut grass silage, the wide-swath advantage is 10%, according to work by Tom Kilcer, a Rensselaer County, NY, extension agent.

But few machines are currently able to lay forage near 80% of their cutting width, says Ron Schuler, a Wisconsin extension ag engineer studying machine swath width.

“As the machines get larger, the swath is going to get narrower percent-wise,” says Schuler. “For every foot increase, on average, there is a 4% decrease in swath width. For the conditioner, the slope is the same.”

For example, a mower conditioner with a 130” cutting width can have its swath adjusted to 94” wide. “That's 68% of the cutting width and the conditioning width is 93”, which is 67% of the cutting width. On another machine, its 144” width of cut gives a 91” swath (63%) and conditioning width is 110” at 75%,” Schuler says.

Swath-width limitations are typically related to the lengths of conditioning rolls, says Schuler. Mower conditioner manufacturers find that adding length to conditioning rolls is expensive.

“They may have the same rolls on a couple of different machines, such as on a 14' ands a 16' machine,” the ag engineer says. That saves manufacturers and growers money, but doesn't help growers who want wide swaths.

In researching swath widths of 72 mower conditioners, Schuler found that only seven models could lay swaths at more than 80% of their cutting width. Another 10 machines had swaths at 70-80% of cutting width, 24 models had swaths at 60-70% and 31 at below 60%. At least 14 models achieved conditioning widths at more than 80% of cutting width; another 10 at 70-80%, 22 at 60-70% and 26 at below 60%, Schuler says.

Most of the mower conditioners that can be adjusted to swath widths near 80% are smaller machines. “Machines down around 9-10' cutting width do a better job of getting to 78-80% swath width,” Schuler admits.

The only self-propelled windrowers that swathed at over 80% of cutting width were a few high-cost machines combining three smaller mower conditioner units. “So if you want to shoot for that 70-80%, there won't be many self-propelleds that do that,” Schuler says.

Wheel spacing with self-propelled machines is also a concern, the ag engineer adds. “We like to get the windrow between the driving wheels, so that's a limitation.”

What all this means is that growers who want wide swaths need to buy mower conditioners capable of adjusting to them. Or they need to adjust their current machines to their widest swath.

“I would say get as wide as you can,” he adds. Although New York data suggests wide swaths should be over 80% of cutting width, Schuler says 78% would be good, too. “But you certainly don't want it under 60%.”

A Wisconsin study by grad student M.E. Herzmann suggests another option. Tedding immediately after cutting spreads out the windrow, letting it dry faster, says Schuler. “What he did was mount a tedder on the back of a self-propelled windrower and tedded it immediately.”

Tedding at cutting increased the crop's drying rate by 54% compared to forage similarly conditioned and placed in a windrow.

Or, Schuler suggests, growers can use old cutterbar mowers and forget conditioning. But those machines are only 6-8' wide, he says.