The influence of seeding rate on weed control in small-red lentil (Lens culinaris)

Experiments were conducted at two sites for 2 yr in the Pacific Northwest dryland cropping region to determine if seeding rate of small-red lentil could enhance weed control with herbicides and increase lentil seed yield. At Pendleton, OR, and LaCrosse, WA, lentil was planted at 22 or 44 kg ha−1in one direction in all plots. In one-half of the plots, lentil was cross-seeded at right angles with an additional 22 kg ha−1to provide seeding rates of 22, 44, 22 + 22, and 44 + 22 kg ha−1. Seeding rate main plots were split into three herbicide treatments and an untreated control. Total weed density was reduced by increasing seeding rate at Pendleton both years when averaged over all herbicide treatments. Seeding rate reduced total weed density to a greater extent when herbicides did not adequately control weeds or when herbicides were not applied at Pendleton in 1992. Increased seeding rate also reduced total weed dry weight at Pendleton in 1992 and 1993 and at LaCrosse in 1993. The suppressive effect of increased seeding rate on weed dry weight was more evident when herbicides were not used or when herbicides gave only partial control. Herbicides generally reduced weed density, but the effectiveness of individual treatments was related to the weed species present and environmental conditions present in each experiment. Lentil aboveground dry weight production increased with seeding rate at both locations; however, only in 1 yr did lentil seed yield increase with seeding rate. The primary benefit from increased seeding rate in this study was to reduce weed density and dry weight.