On Wednesday, Rodney Weinzierl, executive director of the Illinois Corn Growers Association, kept a watchful eye on the weather. He counted three rainstorms moving over the area, each narrowly missing his 500 acres of farmland about 10 miles outside Bloomington, Ill., and allowing him his first opportunity to get on his tractor and plant this year. He worked through the day to get two-thirds of his corn seeds in the ground. Wednesday was the deadline for corn crops to be planted in order for farmers to receive full insurance coverage in most Illinois counties.