Effect of freezing on sudex, millet hay, etc.

Producer Question from 2012

Q.  What effect does freezing have on sudex, millet hay, etc. still standing in the field as far as nitrates are concerned? Can I cut it right after freezing or should it stand awhile? (Sept 26, 2012)

A.  Nitrates are not reduced due to freezing. If the plant has been stressed during the growing season, then the nitrates will be located in the lower part of the stalk. There may be some additional accumulation at the base of the plant after a freeze because of the disruption in plant growth as a result of the freeze. So if you suspect nitrates, set the mower height to 6 to 8 inches instead of cutting close to the ground.

Some of the sudan and sudex may also have prussic acid and prussic is typically higher after a freeze. Prussic acid will decrease after a freeze. In a grazing situation, usually we recommend to wait 7 days after a hard freeze before allowing cattle to graze these plants.

Aaron Berger, Extension Educator
Panhandle Research & Extension Center
University of Nebraska