Thanks for the comment. I've already hit it with N and I expect them to make a pretty good recovery. I just wanted everyone to see that it's really important to stick to recipes and spray evenly. It is possible to damage chufas with most any herbicide.

I just sprayed the planted part and sprayed the weedy area I missed in the volunteer part. I used a mix half as strong as before, but it is really hard to get even coverage with a wand. That whole patch is only .3 of an acre, so it's just something I'm playing around with.