I would stop fertilizing for a good year if not forever (
) and add sand for better drainage when you have heavy soil. That attacks the conditions barnyard grasses like. I would also rip them out manually. From my
experience they are easy to pull, right?
Manually removing the motherplants is back-braking business. But with patience, ambition and changed conditions they shouldn't come back. They really do love an excess of nitrogen. Barnyard grasses only come up in my vegetable patches not in my lawn for this reason...