Turns out, Johnsongrass has good, bad and ugly traits according to Tim Schnakenberg, agronomy specialist, University of Missouri Extension.
The good
From a livestock standpoint, Johnsongrass is a palatable forage. It is high-quality, a good producer, persistent and is drought-tolerant.
“One study I read found that among 14 species tested, Johnsongrass ranked second only to switchgrass in grazing preference,” said Schnakenberg.
The bad
One of the downsides is that Johnsongrass is invasive. It reproduces from seed and underground stems called rhizomes. A single plant has been documented to have as much as 275 feet of rhizomes and as many as 80,000 seeds.
“Johnsongrass competes with other species and can overtake fields and highway right-of-ways,” said Schnakenberg.
The ugly
There is one ugly problem that comes with Johnsongrass.
There have been cows killed as a result of prussic acid poisoning or nitrate toxicity in Johnsongrass and similar forages like sorghum sudan.
“It doesn’t happen on every farm but once in a while we’ve seen and heard of cattle dying when conditions are just right,” said Schnakenberg.
Prussic acid or cyanide can build up in the plant when it’s less than two feet tall and can also occur after a frost in the fall.
Harvesting it for hay will dissipate the prussic acid. Nitrates build up when farmers fertilize it as a crop and the drought prevents the plant from using the nitrogen.
Harvesting it for hay keeps the same level of toxic nitrates as the day it was harvested.
“Tests for prussic acid are hard to come by but the plant can be tested for nitrates.” said Schnakenberg. FG
—From University of Missouri Extension Southwest Regional News Service
