Find the wettest bottom and fence it off. Spray the grass this springwith 3x Round Up and then disk a couple times this summer. Respray after regrowth begins each time.
Soil test ASAP. If your pH is 6.4 or higher plant clover this fall. If not add lime this spring to improve. The disking will incorporate it this summer.
I had a similar situation and it took 3 sprayings and then I retreated with Arrest the following spring. My field looks real good. I may need to spray it one more time this spring.
Most grasses that have been there for a while will leave quit a collection of dormant seed, theycan be a booger to get rid of.
for Arrest info.