Spray with gly and set fire to it. It will burn the grass under and pop the sorghum like popcorn. It will leave you with standing sorghum with very clean ground underneath. Also, you are kinda right by the fact of the birds liking it later in the season. Doves like bigger grain the cooler it gets in part because of the higher fat content. I have saw cut soybean fields not have a dove on them and then a month later a cold front hit and it be loaded down.