An experiment was conducted at Scott and Melfort in 1997 and 1998 to assess glyphosate application 2 to 3 weeks before (early), 1 day before (prior)and 3 to 4 days after seeding (post) in narrow-hoe and simulated-sweep (cultivation immediately followed by a narrow-hoe drill) direct-seeding system.
The tillage effect of sweeps at the time of seeding can improve the control of grassy weeds compared with seeding implements equipped with narrow hoes.
However, a narrow-hoe system with glyphosate applied just prior to sowing consistently provided the greatest cereal yields.
Producer should achieve consistently good weed control and maximum cereal crop yields with the narrow –hoe air-seeding equipment when glyphosate is applied just prior to sowing.
Producers that direct seed with sweep-equipped air seeders should not expect that crop productivity will be maintained if glyphosate applications are made early. Results with sweep systems will be highly dependent on the weed control afforded by the sweeps, as well as the effect of high disturbance sweeps on seedbed moisture.
Document Source: Canadian Journal of Plant Science, Volume 82:611-615
Year of Publication: 2002