Sorry I didn't respond; I saw your post yesterday on my phone and then forget to respond later. I'll try to answer your questions as best I know, which may be wrong:

1) When to apply the PRE depends on which herbicide you use. Treflan has to be incorporated into the soil, so you probably need to do it just before planting. Prowl and Command can be sprayed on right after planting, but both will need rain soon to work.

2) Milestone is the best broadleaf chufa herbicide I've found. Dr. Youngblood in Selma was the first I saw posting about it. It has wiped out some really bad weeds from my fields that I thought would always be there.

3) I've used Poast, Fusilade and Clethodim with good success on grass. I prefer Clethodim. It seems to work best and is cheapest.

4) Mix I use is Clethodim and Milestone.

5) Nothing wrong with using both. If you want perfectly clean fields, probably need both. I've found the mix I'm using now works well enough on my soils that I've quit using a PRE.

I am amazed to hear from people like Stikman who are able to grow chufas without herbicide. If I didn't use them on my fields I would have nothing but a waist high stand of grass and weeds. But all my fields have been in cultivation since the 1820s and have every weed known to the area. I guess the history of the soil and type of soil has everything to do with what you need as far as herbicides. I've had very little problem with insects and have some fields that have been in chufa over 10 years. Yellow nutsedge is the biggest problem in the old fields; very hard to deal with it in chufas.

Good luck with your chufas!

pcp, my biggest problems are pigweed, morning glory and carpet weed and I don't see this listed on the label. I've been using 2,4-db and clethodim. Works pretty well but the carpet weed is the hardest to control

Most of my fields are old loading docks. Once I break ground I let the new growth sprout and then spray with a cheap glyphosate and plant with a 2row planter and straddle the rows so that there is a row every 12 inches. Then broadcast clover afterwards.
This is the only way I've found to cheaply achieve a productive stand of chufas. Now my idea of a productive stand and someone else's idea might vary drastically!

Stikman, if you straddle the rows to plant the next 2 rows, does it not plow up the first 2? I have thought about that for soybeans.

Run the disc over them twice and then run the tiller over them. My 2row planter has a 36 inch spacing for rows and by straddling every other run I get a row every 12 inches that way they have a better chance at shading out the weeds. I do have weeds but the chufas produce plenty of nuts. And they make a fine place for the deer to bed up in. After planting I do not plow. Just broadcast clover and forget about them until the fall and then I start my coon eradication program!!!!!!!

Stikman, could you get me some pictures of your planter? I have a 2 row covington that I might could just remove some of the plows to make it happen. Really smart idea.