Can you identify this grass?

This grass is in one of the ditches on my farm. With my Echo 2620T using Black Diamond or Rotary Vortex, it's like trying to cut wire.

Is there another trimmer line that might be more aggressive? Even taking your time and and not forcing it, this is some mean grass to cut.

Sometimes I keep it sprayed with roundup, sometimes I cut it.

Can you identify this grass. I'm in southeastern N.C.