Organic grain cropping systems depend on a dramatically different set of crop production inputs than do conventional grain cropping systems. Fertility and weed control are two prime examples of the differences involved. There also may be subtle or sharp input differences required to effectively manage diverse organic grain cropping systems. The objective of this research was to compare corn (Zea mays L.) productivity under three divergent organic cropping systems, each including a two-year rotation, with each crop element of each rotation present each year. Systems tested in 2004-08 near Lexington, KY were as follows: a) corn following 18 months of orchard grass/red clover mixed forage, b) corn following hairy vetch, rotated with soybean following winter rye, and c) corn following winter wheat and double crop soybean. Corn was established in each system utilizing conventional tillage and 45 kg ha-1 N (as Nature SafeTM) applied at growth stage V4. At growth stage V8, additional N was applied at rates of 0, 45, 90, and 135 kg ha-1. Weed control measures included 1-2 mechanical cultivations plus hand-hoeing of any noxious weeds (johnsongrass, Canada thistle) which were noted. At physiological maturity, biomass samples were collected for corn and grass and broadleaf weeds. Yields and yield components will be reported. Organic grain cropping systems appear to result in differing corn productivity and to require different management strategies.