Foxtail and crabgrass

I have 25 acres of land grew oats for a Seed Company. It is full of grass now not many broadleaf weeds and hay in demand around here right now and so I was thinking about putting 50 units of n on and harvesting the grass in 30 to 40 days for feed. I done it once before and it worked another time it did not work does anyone ever do this?

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Foxtail and crabgrass