TOLERANCE OF SPRING BARLEY TO TRIFLURALIN DEEP-INCORPORATED IN THE FALL OR SPRING

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Abstract
Field experiments were conducted in 1982 and 1983 to investigate the tolerance of barley (Hordeum vulgare L. ’Galt’) seeded 5 cm deep in a Ponoka loam soil treated with trifluralin. There were eight rates of application from 0 to 3 kg/ha applied in fall and spring and incorporated by means of a rototiller set to till to a depth of 10 cm. All data were analyzed by regression. Gas chromatographic analysis of extracts of soil samples collected in the spring following fall application of trifluralin (0.0–3.0 kg/ha) indicated that approximately 45% of the herbicide was lost regardless of rate applied. Fall application of trifluralin up to 3 kg/ha and spring application up to 1.1 kg/ha did not adversely affect the numbers of barley seedlings that emerged. Trifluralin treatments within the rate range 0.85–1.4 kg/ha caused severe early injury (delayed growth) to barley, the magnitude of which varied with the season and year of application. Fall application caused less injury than the respective spring application during both years. With fall or spring applications up to 1.3 kg/ha or 1.0 kg/ha, respectively, barley yields were not reduced compared to the untreated control. With fall application at 1.4 kg/ha barley yield was reduced in one of the two years. Rates in excess of 1.8 kg/ha caused significant yield reductions with all treatments. The data indicate that trifluralin could be used as a deep-incorporated fall or spring treatment at rates up to 1.3 or 1.0 kg/ha, respectively for weed control in barley in central Alberta. Fall application would improve the safety to the crop. Barley could also be seeded into soil where trifluralin (1.4 kg/ha) was applied as a fall treatment for weed control in rapeseed (Brassica campestris L. and Brassica napus L.), but some loss of yield could be expected.Key words: Trifluralin rate, soil incorporation, barley, tolerance