Agricultural News
Grazing Johnsongrass More of a Possibility with Severe Drought Conditions
Thu, 07 Jul 2011 11:56:50 CDT
Currently, pasture conditions in the Southern Great Plains, including Oklahoma, are continuing to decline due to droughty growing conditions. This has resulted in most pastures starting to have a late-summer appearance. One "forage" that seems to be surviving the drought and doing quite well, in many areas, is johnsongrass. With the lack of adequate grazeable forage, what is the possibility of grazing johnsongrass?
Johnsongrass is very competitive with other forages if left unchecked. It is also drought-tolerant and is often one of the last plants to stop growing during a drought. Johnsongrass yields can approach 3 to 5 tons/acre under good growing conditions. Nutritive value estimates of 10% crude protein and near 60% TDN are common.
In addition to nitrate toxicity potential, another potential negative to utilizing johnsongrass is that it has a high potential to produce hydrogen cyanide (HCN). This is more commonly known as prussic acid. The forages used in Oklahoma that are most likely to produce toxic levels of HCN are the grain sorghums, johnsongrass, sorghum-sudangrass hybrids, and sudangrass.
Safety Measures
During severe droughts, grazing pastures that are mainly johnsongrass should be avoided. Do not rely solely on drought-damaged forages as the only source of forage. It is important to keep some other form of dry forage available at all times.
1. Do not graze cattle if they are hungry. Feed hay and begin grazing in late afternoon.
2. Restrict grazing until plants are at least 24 inches tall. Young, succulent growth and regrowth has greater concentrations of HCN than older more mature growth.
3. Do not graze regardless of height within four days following a good rain. This is time when rapid, new growth of young plant tissue occurs.
4. Do not graze wilted plants or plants with young regrowth. The best management practice will be to harvest this as hay.
For more information on forage HCN potential and testing, please see OSU Fact Sheet PSS-2904 (Prussic Acid Poisoning) or contact your local county extension educator. Daren Redfearn, Extension Forage and Pasture Management Specialist daren.redfearn@okstate.edu
Our thanks to Jeff Edwards, Oklahoma State University Small Grains Extension Specialist, for providing this article through the Extension News. More articles from the Plant and Soil Science Extension News can be found by clicking here.
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