RESPONSE OF FLAX AND LENTIL TO SEEDING RATES, DEPTHS AND SPRING APPLICATION OF DINITROANALINE HERBICIDES

Two field studies were conducted at Morden, Manitoba in 1992 and 1993 to investigate the effect of seeding depth and seeding rate on flax and lentil recovery following spring application of dinitroanaline herbicides. In the first study, the effect of seeding depth on flax and lentil tolerance to ethalfluralin, pendimethalin and trifluralin, applied preplant soil incorporated at 1.1 kg a.i. ha(-1) in the spring, was investigated. Deep seeding (6 cm) reduced flax population density by 59%, averaged over 2 yr, when compared with shallow seeding (3 cm). Ethalfluralin, pendimethalin and trifluralin, reduced flax population density, but the effect of herbicide was less when flax was seeded shallow. Trifluralin and ethalfluralin reduced flax yield more when the crop was seeded deep than when seeded shallow. Herbicide treatments had no effect on flax yield when the crop was seeded shallow. Ethalfluralin and trifluralin reduced lentil population density and seed yield in one year only. Pendimethalin did not reduce lentil population density or seed yield. Deep seeding did not affect lentil population density, seed yield or phytotoxicity of dinitroanalines in this crop. In a second study, flax and lentil were seeded at 15, 30, 45, 60 and 90 kg ha(-1) at 3 and 6 cm planting depths to assess the effect of seeding depth and seeding rate on crop recovery following spring application of ethalfluralin. In ethalfluralin treated plots, seeding rate had to be increased from 60 to >90 kg ha(-1) to achieve similar population densities as 45 kg ha(-1) in untreated plots. Flax yields were unaffected by ethalfluralin when the crop was seeded shallow, but yields were reduced significantly when the crop was seeded deep. Lentil population density increased linearly with seeding rate. Lentil population density was unaffected by seeding depth or herbicide treatment. Ethalfluralin did not reduce lentil yield in either year. Lentil yields increased with seeding rate up to 30 kg ha(-1), with little further increase in yield for seeding rates between 30 and 90 kg ha(-1).