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Reducing ash in winter annual forages

Contributed by John K. Bernard Published on 10 April 2020

Spring is almost here, and winter annuals will be ready to harvest very soon. One problem that seems to be getting worse is contamination of winter annuals with dirt resulting in higher ash concentrations.

All plants contain minerals, which is reported as ash. Typical concentrations are in the range of 8% to 10%, but it is not uncommon to see samples with ash concentration twice that high. This is most often due to how equipment is operated, resulting in soil contaminating the forage. Excess ash interferes with proper fermentation, as soil will contain minerals that act as a buffer and is a source of contaminants such as clostridia bacteria. It will increase rumen fill from inert soil settling to the bottom of the rumen, and soil contamination increases equipment wear. Ash contamination does not provide energy or other useful nutrients. Below are some practices that will reduce ash contamination and improve wilting and fermentation.

  1. Do not cut forage until it has dried. Dirt will be less likely to stick.
  2. Cut the forage at 6 inches rather than close to the ground. This reduces the amount of dirt picked up by the mower and deposited on forage. Having a higher stubble also allows more air to circulate under the forage swath, speeding up wilting time. There is a slight reduction in forage quality by raising the cutting height, but forage harvested should be higher quality, and you also minimize wilting time, which could make the difference, given how rainy it has been so far this year.
  3. Use flat knives on the disc mower rather than angled knives, which create more suction.
  4. A wide swath facilitates drying under normal circumstances, but if the ground is wet, it may be desirable to leave some open space between swaths so the ground can dry before forage is tedded.
  5. When tedding, make sure the tines of the tedder are above the ground and do not scratch the dirt. This minimizes kicking up dirt that will get mixed into the forage.
  6. A drum or power rake is best for minimizing contamination, whereas a wheel rake results in the highest contamination. As discussed for the tedder, make sure the rake is set so it is not scratching the ground and adding dirt to the forage.

These steps will reduce ash contamination and improve forage quality. Remember, forage should be wilted ideally to 45%-50% dry matter to reduce the potential for poor fermentation and production of protein intermediates that reduce palatability and milk yield.  end mark

Reprinted from UGA Extension Georgia Dairyfax.

John K. Bernard teaches dairy nutrition and management and animal and dairy science at the University of Georgia – Tifton. Email John K. Bernard.