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Crop Connection Newsletter

October 12,  2016                                                         Vol. 2,  Issue 14

Frost and Forages 


The weather forecast is calling for temperatures to dip close to freezing tonight (10/12/16), which could mean that we may see a light frost. What does this mean for forage crops, particularly forage crops such as Sorghum-Sudan?

A frost event, even a light frost, with Sorghum-Sudan causes prussic acid to build up in the forage. Special steps should be taken  to manage the forage to prevent prussic acid poisoning with livestock.

Dr. Steve Barnhart, retired Extension Forage Specialist, wrote the articles "Prussic Acid Poisoning Potential in Frosted Forages" and "Flurry of Forage Questions Come with First Fall Frost and Freeze." These articles include some great tips on how to manage frosted forages. 

Some key points that Dr. Barnhart shared in these articles on managing frosted forages like Sorghum-Sudan include: 
  • Do not graze on nights when frost is likely. High levels of the toxic compounds are produced within hours after a frost.
  • Immediately after frost, remove the animals until the grass has dried thoroughly. Generally, the forage will be safe to feed after drying five to six days.
  • Do not graze wilted plants or plants with young tillers or new regrowth. If new shoots develop after a frost they will have high poisoning potential, sudangrass should not be grazed until the new growth is at least 18 to 20 inches (24 to 30 inches for sorghum-sudangrass).
  • Frosted/frozen forage should be safe once baled as dry hay. The forage can be mowed any time after a frost. It is very rare for dry hay to contain toxic levels of prussic acid. If the hay was not properly cured, it should be tested for prussic acid content before feeding.
  • Waiting five to seven days after a frost to chop frosted forage for silage will limit prussic acid risks greatly.
  • Delay feeding silage for 8 weeks after ensiling. 
Note that other common forages like alfalfa, clovers, and cool-season perennial grasses do NOT produce toxic compounds and can be fed safely, just be aware that there is a higher potential for bloat when grazing legumes within a day or two after a killing frost. 
Grain Storage Management 
If you are storing your own grain be sure to follow the proper procedures to help ensure you won't have surprises later. Charlie Hurburgh, Extension Grand Handling and Processing Specialist, shared some great tips in this oldie, but goodie ICM article
Upcoming Events
Ag Chemical Dealer Update  
Nov. 22, 9 a.m. 
Iowa City, IA 
More details can be found here
Integrated Crop Management Conference 
Nov. 30 - Dec. 1 
Ames, IA 
More details coming soon here
Crop Advantage Series 
Jan. 6, 2017: Burlington
Jan. 11, 2017: Ames 
Jan. 12, 2017: Honey Creek (Moravia)
Jan. 17, 2017: Atlantic 
Jan. 25, 2017: Iowa City
Jan. 27, 2017: Davenport 

More details found here

In this Newsletter:

Frost and Forages

Grain Storage Management 

Upcoming Events 
Rebecca Vittetoe
Field Agronomist

Office: 319-653-4811
Cell: 712-540-3319

Twitter: @rkvittetoe

Appanoose, Davis, Jefferson, Lucas, Mahaska, Marion, Monroe, Van Buren, Wapello, and Wayne Counties
Additional Resources:
Integrated Crop Management
Ag Decision Maker
ICM News
Plant & Insect Diagnostic Clinic
Weed Science
Soil Fertility
ISU Mesonet
Iowa Learning Farms
Organic Agriculture
Connect with your Field Agronomist &
the ISU Crops Team
Copyright © 2016 Iowa State University Extension & Outreach, All rights reserved.

Iowa State University Extension and Outreach programs are available to all without regard to race, color, age, religion, national origin, sexual orientation, gender identity, genetic information, sex, marital status, disability, or status as a U.S. veteran. Inquiries can be directed to the Director of Equal Opportunity and Compliance, 3280 Beardshear Hall, (515) 294-7612.

Cooperative Extension Service, Iowa State University of Science and Technology, and the United States Department of Agriculture cooperating.

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