If it's anything like nutgrass...if you leave even ONE bit of root, it will take off the next spring.
I got some nutgrass in a load of mushroom compost years ago. It was a small area of about 9 sq ft. I got down on my knees with a small shovel and spent the afternoon tracking down every bit of root I could find. Thought I had gotten rid of it. The next year you would have thought I poured a gallon of miracle grow on it. I finally nuked it with a cocktail of various herbicides. Did the job and I quit growing crops in that area.
