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Hay rake type impacts ash content in hay

Differences were found in ash content of hay based on the type of hay rake used:

  • Hay raked with a wheel rake contained the most ash.
  • Hay raked with a merger and sidebar rake contained the least amount of ash.
  • Rake-type rarely impacted the nutritive value of hay.

Best practices to reduce ash in hay:

  • Cut wide swaths.
  • Set cutting height at 2 inches or more.
  • Use flat mower knives.
  • Use hay merger or sidebar rake.

What is ash? 

Ash is the total mineral content of forage. Internal ash is the naturally occurring minerals found in plants, some of which have nutritional value to livestock such as calcium, potassium and phosphorus. On average, grass forages have 6 percent internal ash while alfalfa has 8 percent internal ash.

External ash is undesirable soil contamination that can accumulate in hay during raking. It provides no nutritional value to livestock and adds unnecessary weight to purchased hay, which increases cost. Excessive ash content may reduce milk and meat production, lead to sand colic in horses and reduce the amount of nutrients an animal can absorb.

Testing hay rakes

Research conducted by the University of Minnesota, Pennsylvania State University and the University of Wisconsin evaluated four types of hay rakes and their contribution to ash content in alfalfa hay. A merger, rotary-rake, sidebar, and wheel rake were evaluated at all locations during two cuttings in 2015. Hay samples were collected during the four phases of harvest: standing forage, and after cutting, raking, and baling. The samples were analyzed for ash content and forage nutritive values. Hay rakes were used according to manufacturer recommendations and at standard speeds.

The research showed that hay rake type affected ash content post-raking. The wheel rake consistently resulted in the greatest ash content, while the hay merger and sidebar rake resulted in the least amount of ash. Ensuring rakes are adjusted and operated according to manufacturer recommendations will help reduce ash content.

Hay merger
Rotary rake
Rotary rake
Sidebar rake
Sidebar rake
Wheel rake
Wheel rake

Excessive ash affects the cost of feeding livestock 

In Minnesota first-cutting hay, the wheel rake resulted in 14.6 percent ash while the hay merger resulted in 11.4 percent ash after baling. If a livestock producer fed 25 pounds of alfalfa hay containing 14.6 percent ash (or 6.6 percent external ash), they would be feeding 1.6 pounds of soil to their livestock daily compared with 0.8 pounds of soil if the hay contained 11.4 percent ash (or 3.4 percent external ash).

Excessive ash content can also be problematic when buying hay. Using the same values as above, 1 ton of hay containing 14.6 percent ash would contain 132 pounds of soil compared with 68 pounds of soil when the ash content was reduced to 11.4 percent. At an average cost of $150 per ton, a hay buyer would be spending $9.90 per ton on soil contamination for hay raked with a wheel rake compared with $5.10 per ton on soil contamination for hay combined with a hay merger.

Using a hay merger or sidebar rake to combine swaths resulted in less ash content compared to a wheel rake; however, rake-type rarely impacted the nutritive value of the hay. In addition to wide swaths, cutting heights at or above 2 inches, and flat mower knives, the use of a hay merger or sidebar rake can be added to the list of best management practices to reduce ash content in alfalfa hay.

For more information 

Download a two-page summary of the full report.

A full manuscript is available in the Agronomy Journal (“Hay Rake-Type Effect on Ash and Forage Nutritive Values of Alfalfa Hay”)

Abby Neu, poultry Extension educator; Craig Sheaffer, professor of agronomy and plant genetics, College of Food, Agriculture and Natural Resource Sciences; Scotty Wells, Extension forage and cropping system agronomist; Krishona Martinson, equine Extension specialist; Marvin Hall and Dan Kniffen, Pennsylvania State University; and Dan Undersander, University of Wisconsin


Funding for this research was possible through the USDA-NIFA Alfalfa Seed and Forage Systems Research Program and was a collaboration between the University of Minnesota, Pennsylvania State University and the University of Wisconsin. The authors acknowledge the cooperation of Leaning Pine Farm and thank New Holland Agriculture for the use of the hay merger in Minnesota.

Reviewed in 2019

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