Plant population effects on corn hybrids differing in ear growth habit and prolificacy

Terminology characterizing differences in ear growth habit and prolificacy is commonly used by seed companies to relate corn (Zea mays L.) hybrid yield potential to varying plant populations. Little information is available to document the significance of various ear response types associated with commercially available Corn Belt hybrids. The objective of this study was to assess hybrid x plant population interactions of commercial corn hybrids differing in ear growth habit and prolificacy. Field experiments were conducted in 11 environments in Ohio during 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 population associated with ear type were compared at three plant populations (16 000, 24 000, and 32 000 plants/acre). Grain yields, ears per plant, and stalk lodging varied with hybrid and plant population in both years. The semiprolific hybrid and the fixed and flex single ear hybrids exhibited similar yield response to plant population across a wide range of environmental conditions. In 1990, grain yields were greatest for the flex (LH51 x LH119) and fixed (B73 x LH38) single ear hybrids and semiprolific (LH123 x LH93) hybrid at 32 000 plants/acre and the prolific (LH132 x DM2) hybrid at 24 000 plants/acre; whereas in 1991, under drier, hotter conditions, yields for all four hybrids were greatest 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 plant population. Although the prolific hybrid exhibited relatively high yields under stress in 1991, its greater predisposition to lodging limits its potential use in Eastern Corn Belt environments where diseases and weather conditions make stalk quality a major factor in hybrid selection. The relatively minor role that hybrid x population interactions 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 determining optimum plant populations.