PLANT-DENSITY, MATURITY AND PROLIFICACY EFFECTS ON EARLY MAIZE

Several early maize (Zea mays L.) ideotypes were evaluated to determine if maturity or prolificacy differences were important determinants of responses to variable plant densities. Sixteen hybrids were tested at 24,000, 48,000 and 72,000 plants ha-1 in four North Dakota [USA] environments. These 16 hybrids represented a 2 .times. 2 factorial arrangement of maturity (ear moisture at harvest) and prolificacy (ears per plant), with four randomly selected hybrids representing each combination of factors. Grain yield, ear moisture at harvest, stalk and root lodging, test weight and yield components were evaluated. No significant maturity .times. plant density or prolificacy .times. plant density interactions were detected although trends were for early hybrids to yield relatively better at higher plating densities. In the four environments, early hybrids outyielded late hybrids and prolific hybrids outyielded nonprolific hybrids. Early hybrids had higher test weights, more stalk lodging, heavier kernels and more ears per plant than late hybrids. Prolific hybrids had higher yields, lower test weights, lighter kernels, more ears per plant and more root lodging than nonprolific hybrids. For the four environments tested, the highest density produced the highest average yields. The data supported the use of early, prolific hybrids at medium to high densities. However, early prolific hybrids grown at high plant densities had increased root lodging, stalk lodging and higher moisture at harvest.