Effects of competition on yield and dry matter distribution in maize

Timing and intensity of competition, as a function of plant density and other factors, significantly affect grain and total dry matter production in maize. Competition during different stages of growth affects dry weight distribution among different plant fractions. Greater inter-plant competition occurred in hybrids than in inbreds, and in high densities than in low densities, when this was measured as final dry weight per plant. This intraspecific competition began earlier than 6 weeks from planting, the earliest time of thinning included in the trial. The spatial arrangement of planting maize, high density of associated beans, aggressive bean varieties and an earlier bean planting date all reduced maize yields, but showed no significant effect on dry matter distribution. Plant height was reduced by competition. In density trials, yield increased up to 8 x 10(4) plants/ha in experimental plots. Farm trials confirmed this density response under a range of conditions, and indicated the potential importance of this agronomic practice to increase yields with no major change in cropping system or increased production costs eng