PLANT-POPULATION EFFECTS ON CORN HYBRIDS DIFFERING IN EAR GROWTH HABIT AND PROLIFICACY

Terminology characterizing differences in ear growth habit and prolifi cacy is commonly used by seed companies to relate corn (Zea mays L.) h ybrid yield potential to varying plant populations. Little information is available to document the significance of various ear response typ es associated with commercially available Corn Belt hybrids. The objec tive of this study was to assess hybrid x plant population interaction s of commercial corn hybrids differing in ear growth habit acid prolif icacy. Field experiments were conducted in 11 environments in Ohio dur ing 1990 and 1991. Four hybrids(LH119 x LH51, B73 x LH38, LH132 x DM2, and LH123 x LH93) chosen to represent different responses to plant po pulation associated with ear type were compared at three plant populat ions (16 000, 24 000, and 32 000 plants/acre). Grain yields, ears per plant, and stalk lodging varied with hybrid and plant population in bo th years. The semiprolific hybrid and the fixed and flex single ear hy brids exhibited similar yield response to plant population across a wi de range of environmental conditions. rn 1990, grain yields were great est for the flex(LH51 x LH119) and fixed (B73 x LH38) single ear hybri ds and semiprolific (LH123 x LH93) hybrid at 32 000 plants/acre and th e prolific (LH132 x DM2) hybrid at 24 000 plants/acre; whereas in 1991 , under drier, hotter conditions, yields for all four hybrids were gre atest at 24 000 plants/acre. Prolificacy was most pronounced in LH132 x DM2 and at the low plant population; it was least evident in LH119 x LH51 and at the high plant population. Stalk lodging was greatest in the prolific and semiprolific hybrids and at the high plant population ; it was negligible in the fixed single ear hybrid and at the low plan t population. Although the prolific hybrid exhibited relatively high y ields under stress in 1991, its greater predisposition to lodging limi ts its potential use in Eastern Corn Belt environments where diseases and weather conditions make stalk quality a major factor in hybrid sel ection. The relatively minor role that hybrid x population interaction s played in determining grain yield compared with environment, hybrid, and plant population main effects suggests that hybrid differences in ear growth habit and prolificacy are of limited importance in determi ning optimum plant populations.