When tackling grassweeds, delayed drilling will normally bring significant benefits for applying pre emergence herbicides. In particular, by allowing stale seedbed techniques to be used to remove early flushes of grassweeds. Shallow cultivations (often followed by rolling) are often necessary to create the conditions for weed seeds to germinate. Deep drilling, or deep cultivation as part of the drilling process, should be avoided as this can distribute weed seeds over a deeper profile making weed control less effective.
Drilling – Pre Emergence Herbicides: Current Best Practice
For winter wheat, delayed drilling can be a risky strategy but where weather and soil conditions allow this can allow opportunities for weed control before sowing the crop. This can also have benefits in terms of disease and insect pests.
If the weather allows, do not start drilling too early and use good quality seed at a high enough seed rate to get excellent germination and at the same time minimise weed numbers and competition. Ensure your drill is calibrated and set correctly and watch out for any potential blockages.
Seed rates do depend upon the variety, the timing, the quality of the seedbed and the type of soil. If you have any doubts talk to your seed merchant or agronomist.