At 1945 central time, an Engineering and Research Corporation 415-D collided with a corn crop while making a low approach over a private airstrip at Harvard, Ill. The pilot was not injured. The pilot said he planned the low approach at 100 feet agl to determine if he could see the unlit airstrip well enough to land. The airplane flew into the corn crop about two-tenths of a mile from the airstrip and was substantially damaged.