Field experiments were conducted in 2016 and 2017 to evaluate the effects of seeding rate and herbicide programs on weed control and pinto bean yield under irrigation. The experiments comprised a 5 × 5 factorial randomized complete block design with five replications. The weed control treatments comprised a nontreated control, hand-weeded control, EPTC + ethalfluralin PRE, EPTC + ethalfluralin PRE followed by (fb) dimethenamid-P POST at V1, and EPTC + ethalfluralin PRE fb bentazon/imazamox POST. There were five seeding rates ranging from 247,000 to 494,000 seeds ha^–1 planted in 19-cm rows. Weed biomass was reduced by 6 kg ha^–1 with every additional 1,000 seeds ha^–1. EPTC plus ethalfluralin fb either dimethenamid-P or bentazon plus imazamox reduced weed biomass by at least 29% compared to the nontreated control. There was a significant effect of weed control treatment on pinto bean yield (P = 0.0004). However, there was no significant seeding rate (P = 0.42) or seeding rate–by–weed control interaction effect on pinto bean yield (P = 0.38). Pinto bean yield ranged from 3,080 kg ha^–1 in the nontreated control to 4,740 kg ha^–1 hand-weeded treatment. Increased seeding rate in narrow rows is a cultural practice that can improve weed control in pinto bean but may not necessarily increase yield.

Nomenclature: EPTC; ethalfluralin; dimethenamid-P; bentazon; imazamox; pinto bean, Phaseolus vulgaris L.