FIELD PEA CULTIVAR AND WEED RESPONSE TO CROP SEED RATE IN WESTERN CANADA

Weed competition is a serious limitation to field pea (Pisum sativum L .) production. Trials were conducted in northeastern Saskatchewan to d etermine the effects of field pea growth habit, stand density and herb icide treatments on weed growth and on field pea stand and yield. Cent ury, a long-stem leafy type, Tipu, a long-stem semi-leafless type, and Express, a short-stem leafy type, were seeded at 6, 12, 25, 50 and 10 0 seeds m(-2). Some of each cultivar was unsprayed sprayed with a seth oxydim-metribuzin tank-mix for control of grass and broadleaf weeds. F ield pea growth habit (cultivar) did not affect number of weeds, but i ncreasing stand density (seed rate) reduced weed numbers in all 3 yr. Express reduced above-ground dry matter production of broadleaf weeds in 1988 and 1991. Increasing seed rate reduced above-ground dry matter production of weeds in all 3 yr. Field pea yield increased with incre asing seed rate to a rate between 50 and 100 seeds m(-2). Herbicide ap plication reduced weed dry matter production, with the largest effect at low field pea populations. Despite differences in growth habit, the three cultivars competed similarly with weeds. High populations of fi eld peas competed well with weeds and may not require herbicide applic ation, but if producers retain thin stands, good weed control will be critical to attaining high crop yield.