CORN GROWTH AND YIELD IN AN ALFALFA LIVING MULCH SYSTEM

Reduced or no tillage living mulch systems for corn (Zea mays L.) production after alfalfa (Medicago sativa L.) have the potential to reduce soil erosion and water pollution. Available soil water may be the most limiting factor in use of living mulch systems in the north central states. Our objective was to compare growth and yield of corn seeded no-till into chemically suppressed and unsuppressed alfalfa sods to corn seeded using a conventional till system (alfalfa moldboard plowed) with and without irrigation. Alfalfa suppression treatments were: (i) no suppression; (ii) partial suppression achieved by chemically killing alfalfa in 15-in. bands over the corn row using atrazine; (iii) partial suppression achieved by a broadcast application of atrazine; (iv) total suppression achieved by a broadcast application of glyphosate followed by atrazine; and (v) total suppression achieved by moldboard plowing 5 d before seeding corn (conventional system). Treatments were applied to alfalfa following a late-May harvest. Corn was planted in early June. With irrigation, corn grain yields were similar for the partial and total suppression treatments both years. With no irrigation, however, corn grain yields in the partial suppression-band treatment were reduced 46% in 1985 and 55% in 1987, compared with the total suppression-tillage treatment. Corn grain yields in the partial suppression-broadcast treatment were similar to those of the total suppression-tillage treatment in 1985, but were reduced 38% under low rainfail in 1987. When alfalfa was not suppressed, corn grain yields were reduced 63% or more under irrigated conditions and 96% or more under nonirrigated conditions. Producing corn in a partially suppressed alfalfa living mulch system following removal of a spring alfalfa crop may be feasible in growing seasons that begin with fully charged soil water profiles or in areas where irrigation is possible; however, the practice is too risky for routine use in much of the uppwer Midwest.