another johnsongrass question

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Jun 9, 2015
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southern Oklahoma
Newbie to cattle here. Just moved my 4 heifers from one 8-acre pasture to another. They grazed their preferred native grasses down to about 10-12 inches or so. Have loads of 6 ft tall johnsongrass all over. They stripped leaves off of maybe 40% and ate some stalks. But have prob 2 acres still standing tall. Gonna move them back to this pasture in about 6 weeks--do I mow down the mature JG (thinking stimulate more palatable new growth) or just let it be and they''ll get to it sometime this winter? I'm in south-central Oklahoma. Thanks!
Why are you moving them off of it? I would leave them on it now until the Johnson Grass is just stems. It won't be as good in 6 weeks and maybe become dangerous in that time frame.
bird dog":3a8sj5q6 said:
Why are you moving them off of it? I would leave them on it now until the Johnson Grass is just stems. It won't be as good in 6 weeks and maybe become dangerous in that time frame.

They are going back and re-grazing the other grasses instead of finishing off the Johnson grass. Ideally I would put up some electric fence and force them onto just the Johnson grass, but can't really do that. I feel like if I mow it, it'll be back to 24" tall in 3 weeks and be a lot more palatable when I bring them back to this pasture 6 weeks from now. I think if I wait long enough, I can avoid the potential toxicity of that initial new growth.
I believe you are correct with your thinking. I'm not sure how much will grow back. I doubt it will grow 24" this late in the year but getting rid of the stalks would eliminate most of your chance for a toxicity problem. Any regrowth would be eaten quickly like you said.
As dry as it has been here in SW OK, before moving them back, I'd take the stuff and have it tested. Drought conditions can make Johnson Grass dangerous. We lost a cow that got into some back in 2012 during the drought here. She found one tiny patch in one corner of a pasture and it dropped her quick. As long as it's OK, then let 'em go at it. And as they have said, don't let them near it after a frost.
Before I would just mow it down I would bale it. We just cut some hay fields loaded with Johnsongrass and I guarantee the cows will eat those bales quicker than the clean grass bales.
I generally only worry about nitrates in damaged/drought stressed FERTILIZED johnsongrass... if no N fertilizer applied this year, I'd not be worried about 'em grazing it.
Prussic acid (HCN), on the other hand, is still a concern, however, if standing JG is damaged by hail, frost, etc.
We are in a drought. The only thing growing right now is weeds (the ones with the Carrot root), JG and SS. Young, tender shoots are always more appealing and digestible but with weather stress you have to be careful with potential Prussic Acid poisoning when grazing. Also with mowing, the plant stays in, or moves back into the growth mode rather than sit there with what it has in the mature-dormant mode.

Plenty of info available, herein and elsewhere on how to avoid weather related PA problems. If all else fails, on new growth, let it get up a foot or so (PA problems worse in lower-shorter growth) and turn in a scrub cow (one you can do without if the worse happens) on it. If she survives, run in the rest.
Johnson grass makes great hay when cut in the boot. In the boot means the seed heads has not came out of the shoot. A well managed Johnson grass meadow will yield some great hay.
Speaking of cutting for hay.. We have a big Field of it but would like it thicker.. when is the right time to cut the roots with a disc to assist in spreading?
Mow it, keep the cows off. It will be back. Moisture will help. In my heavy clay soil, we were in a drought most of the summer, cracks deeper than you could measure, some 8" wide, JG and SS were the only things growing. I had 4 different sproutings after 3 haying operations and was still coming back up when these rains hit.

Problem with regrowth and grazing is trying to figure out if the pasture is under stress where Prussic Acid may be a concern. Lots of published data on that potential problem.

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