Research in irrigated and nonirrigated corn production systems was conducted to evaluate the effect of leaf architecture of corn hybrids on weed management. The corn hybrids used in each study were ‘Pioneer 3394’ (upright leaf) and ‘Pioneer 3260’ (horizontal leaf). In the irrigated study, residual weed control treatments included two rates of prepackaged mixtures of metolachlor plus atrazine, encapsulated acetochlor plus atrazine, nonencapsulated acetochlor plus atrazine, or a tank mixture of simazine and metolachlor plus atrazine. In the irrigated experiments, horizontal leaf architecture reduced weed density (all three sites in 1 of 2 yr), weed biomass (five of six sites), solar radiation reaching the ground (all six sites), and weed seed production (one site each year) compared with upright leaf architecture. Weed density and weed biomass did not differ between herbicide rates or acetochlor formulation at any site. Corn hybrid was significant for yield at only one site. Reduced weed biomass did not translate into yield differences. The nonirrigated study evaluated two factors at four sites over 2 yr: leaf architecture (upright or horizontal leaf) and weed management program (preemergence residual and postemergence no residual) at two application rates. Neither weed density nor weed biomass was reduced because of corn leaf architecture or herbicide rates in the nonirrigated study. No interaction was detected in either irrigated or nonirrigated studies between leaf architecture and herbicide treatments, indicating that these factors are independent of one another. On the basis of these studies, it appears that horizontal leaf architecture of corn hybrids can assist in integrated weed management in irrigated corn production but may not be beneficial when corn is grown under drought-prone conditions.

Nomenclature: Acetochlor; atrazine; metolachlor; simazine; corn, Zea mays L. ‘Pioneer 3260’, ‘Pioneer 3394’.