I plant 1-2 acres after sweet corn for my wife who is a photographer as well. I have done it for 2 years. I disc the ground a few times, spread oil seed sunflowers with a shoulder mount spreader that are sold as bird seed, lightly disc them in 1 time and then spray Prowl H20 and Dual on top with about 10 gals of Nitrogen as a carrier. I have been lucky enough to plant them right before a rain both times. My variable rate seeding has yielded in amazing sunflowers that "bloomed" for about 14-18 days both years. Both years they stood well until about 14 days after they stopped blooming and then they lodged pretty bad. I would estimate my population was 40-80,000 because I don't need them to stand very long and I want a solid sunflower look. Keep in mind that I didn't plant them until late July to early August.