Pounds of seed per acre? More like ounces. I hand turned my planter and captured the seed to determine my drop rate aiming for 20,000 plants per acre. When I finished, I counted the seeds I had captured. It amounted to about the amount of seed you could scoop with one hand. There were 500+ seeds in a handful! I'd guess your looking at around a "gallon" of seed per acre for row planting, twice that for broadcast. I'd guess a gallon of sunflower seed at about 2 1/2 or 3 lbs. Not much.