Steve,
As you have a lot of Johnsongrass out there, I would think about buying Outrider. It is one of best products I have seen on the sedges and also does well on the Johnsongrass. However, I feel pretty confident it will smoke your chufa as well. If you have an area you want to put in chufa next year, you can spray it before you plant your chufa. There are restrictions on planting back with some crop species, I think corn can be a year or longer. Soybeans could be planted sooner. You will need to check the label. It is a fairly expensive material.

If you do the things you need to do when you need to do them then someday you can do the things you want to do when you want to do them.