Fig. 1. Corn grain yield (Mg ha^–1) in (a) 1990, (b) 1991, and (c) 1990–1991 average after cover crop and kill-date treatments of: rye killed early (RYP) or late (RYL), vetch killed late (VTL), vetch–rye mixture killed early (MXP) or late (MXL), or no-cover (CKL).