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Leave forage ash in dirt
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Leave forage ash in dirt

WISCONSIN DELLS, Wis. – Feeding dirt doesn’t do much for milk production. That’s why a cloud of dust during forage-harvest operations is more than a nuisance.

Failing to consider ash in forage can result in overestimating forage value. Ash is the total mineral or in-organic content of forage. While naturally occurring ash does contain minerals such as calcium, magnesium, potassium and phosphorus, surface ash is mostly silica, dirt or sand bedding. And cows don’t produce eating dirt.

Ash takes the place of forage nutrients on an almost 1-to-1 basis. For each 1 percent ash, total digestible nutrients decrease 0.98 percent, according to Dan Undersander, University of Wisconsin-Madison emeritus forage specialist. He recommends a goal of making forage with 10 percent or less total ash.

Abby Neu, University of Minnesota-Extension livestock educator at Willmar, Minnesota, tackled the topic of ash at the 2018 Midwest Forage Symposium in Wisconsin Dells. She said farmers should be concerned about ash in forage because not only does it dilute nutritive value, it lowers forage intake and reduces digestibility. A 1 percent increase in ash on a dry-matter basis amounts to about a 1 percent decrease in total digestible nutrients.

She said grasses, on average, contain 6 percent naturally occurring ash; alfalfa contains 8 percent. She said forage tests report total ash instead of differentiating between naturally occurring ash inside plants and surface ash. Surface ash is the portion farmers can do something about.

Neu said analysis of 1,000 forage samples submitted to the University of Wisconsin’s Soil and Forage Analysis Laboratory revealed the difference between types.

  • Average ash content was 12.3 percent for haylage, in a range of 5.7 percent to 18 percent.
  • Hay samples averaged 10.3 percent ash, in a range of 8.8 percent to 17.6 percent.
  • Percent surface ash can be estimated by subtracting typical internal-ash amounts – 6 percent for grass hay or 8 percent for alfalfa haylage – from total ash in the forage-test report. Undersander said grass and alfalfa both averaged 4 percent surface-ash contamination. But some samples contained 18 percent total ash.

“This means the animals consuming this forage were eating almost 1 pound of dirt in each 5 pounds of hay or silage,” he said.

Minnesota, Wisconsin and Pennsylvania joint research looked at ash contamination. That contamination was from three types of rakes – sidebar, wheel and rotary — and a merger used in alfalfa. Neu said the merger showed the least contamination, while the wheel rake resulted in the greatest percentage of ash.

“Wheel rakes tend to incorporate more ash because they are ground-driven,” Undersander said.

Neu said farmers using wheel rakes should pay close attention to travel speed. Check the manufacturer’s recommendation. Ensure wheels are appropriately set and readjust the setting before every harvest during the growing season.

“Rake hay off stubble instead of doing tillage with the rake,” she said.

Undersander said raising a cloud of dust while raking can add 1 percent to 2 percent ash to hay.

Several actions can minimize ash forage.

Don’t harvest lodged forage –

  • Though it can’t always be avoided, growers can plant varieties that stand better. They can also harvest early to reduce lodging potential.

Raise the disc-mower cutter bar –

  • It will lower ash contamination and raise forage quality but reduce yield. The sweet spots are 3 inches for alfalfa and 4 inches for legume-grass mixes.

Use flat disc-mower knives –

  • Flat knives pick up less ash during mowing.

Keep windrows off the ground –

  • Lay wide swaths of cut forage onto dense stubble to eliminate harvesting a layer of soil on the bottom of windrows. Neu said forage dries better in a wider swath and will maybe lose some ash contamination during drying.

Minimize moving hay horizontally with a rake –

  • Undersander said it’s better to move two swaths on top of a third in the middle than raking everything to one side.

Use a windrow merger if possible –

  • Evidenced by the three-state study, mergers result in less ash because the windrow is lifted and moved horizontally by a conveyor rather than being rolled across the ground. Undersander said merging can result in 1 percent to 2 percent less ash in hay or silage.

Match equipment to field size –

  • If forage is harvested on uneven and rolling ground, a wheel rake that opens to 21 feet might not be the best choice, Neu said.
  • Ash contamination can also occur during storage and feeding. Store forage piles and bags on concrete or asphalt to minimize dirt contamination. Storing harvested feed on dirt adds dirt to feed during feed handling, especially when it’s wet and muddy.

Excessive ash content can be problematic when buying hay. If purchasing hay direct from a farmer, the buyer might ask if the hay was raked or merged. Try to determine if best-management practices were followed.

Email or call 320-235-0726 for more information.

Jane Fyksen writes about crops, dairy, livestock and many other agricultural topics; she is the crops editor for Agri-View based in Wisconsin. Email for more information.

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A three-state study compares three types of rakes and merging and ash contamination in various stages of forage harvest.

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