Seeding can begin fairly soon after a burnoff — but take note of the weeds present.
For annuals and winter annuals, glyphosate needs only 24 hours to get to the growing point. After a day, the crop can be seeded.
For perennial weeds, 3 days should be enough in sunny and warm conditions but 5 days is recommended before seeding if weather is cloudy or cool.
Contact products will have done their job in the time it takes glyphosate to work.