What is the appropriate control for an experiment on the effect of nitrate fertilizer on germination of sunflower seeds?

Umm...NOT putting nitrate fertilizer on the seeds in a second planting? Apparently they're not teaching the scientific method in science class any more, so let's set this experiment up properly. You want to test the effect of nitrate fertilizer on sunflower plants. You will need: some plantable sunflower seeds--go to a garden center for these. I saw a kid try a sunflower growing experiment once. He planted seeds and they didn't grow. The teacher asked him where he got the seeds..."at Torchie's." Torchie's was a gas station, and he bought roasted sunflower seeds. Those won't grow at all. Anyway, you can't go to Torchie's anymore because Mr. Torchie sold his store to someone else. But don't go there anyway. some potting soil. two planting trays. some nitrate fertilizer. two watering cans. Label one "with fertilizer." Plant the same number of seeds in both trays in soil from the same bag. Label one "with fertilizer" and one "without fertilizer." Just water the "without fertilizer" tray. Use fertilizer according to directions on the label on the "with fertilizer" tray. Except for the fertilizer, don't do anything different--put them in the same window, make sure the cat doesn't get in either tray, don't give any other reason for one tray to grow better than the other. Keep records of which one grows better. This is a good, easy, fun experiment.