FACTORS INFLUENCING THE TOLERANCE OF BARLEY TO FALL-APPLIED TRIFLURALIN

Abstract

The effects of cultivar × date of seeding and of depth of seeding × date of seeding on the tolerance of barley (Hordeum vulgare L.) to a granular formulation of trifluralin [2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl) benzenamine] applied the fall prior to seeding were studied in field experiments from 1982 to 1985 at Beaverlodge, Alberta and from 1983 to 1985 at Lacombe, Alberta. At Beaverlodge, barley yields were generally unaffected by trifluralin at 1.1 kg (active ingredient) ha−1, while at Lacombe they were not affected by the herbicide at rates to 1.4 kg ha−1. In the single incidence where barley yields were reduced by the 1.1 kg ha−1 rate at Beaverlodge (i.e. yields were 30% lower from plots sprayed with trifluralin at this rate than from unsprayed plots) moisture stress following crop emergence appeared to increase stress from the herbicide. Injury occurred from trifluralin at rates above 1.1 kg ha−1 at Beaverlodge and 1.4 kg ha−1 at Lacombe. No differences in tolerance to the herbicide were observed among 10 cultivars seeded at Beaverlodge or 4 cultivars seeded at Lacombe. Similarly, no consistent trends in the tolerance of barley to trifluralin were observed as a result of depth of seeding or its interaction with date of seeding. Losses in yield caused by the herbicide were no greater when the barley was seeded as early as possible in the spring into cool soils (mean weekly soil temperatures as low as 5.2 °C) than when it was seeded later in the spring when soil temperatures were above 10 °C. Also, yield losses due to herbicide injury were no greater for barley seeded at a depth of 10 cm than for barley seeded at a depth of 5 cm. Keywords: Trifluralin, barley, cultivar, seeding depth, seeding date