Sowing at the recommended time for the crop type and variety will maximise the competitive ability of the crop, which in turn will reduce weed biomass and seed-set.
Time of sowing has a large effect on early crop vigour, canopy development, dry matter production and final yield, and all these factors have a direct impact on the competitive ability of a crop. Delaying sowing reduces these factors, giving the weeds an advantage.
Delaying sowing beyond the optimum window recommended in a given district will reduce early vigour, extend the time taken to reach canopy closure and reduce overall dry matter production. It is therefore important to sow within the recommended time period, not only to maximise yield but also to make the crop competitive.
When using delayed sowing to allow for control of the first germination of weeds, choose the crop type and variety most suited to later sowing to minimise yield loss. Preferably use crop types and varieties that can be successfully sown later, such as field peas, chickpeas, barley or short season wheat.
Sow problem weedy paddocks last to allow a good weed germination and subsequent weed removal prior to sowing. As delays in sowing lead to a rapid decline in yield in several key crop types, significant delays are rarely used as a planned strategy. However, a widely adopted approach is to plan to sow weedy paddocks last. The sowing operation as a whole is not delayed, and the benefit of delayed sowing (such as grazing or flaming) is applied to paddocks where it is needed most.
Article: CulturalWeedControl174 (permalink) Date: 9 January 2013; 7:48:37 PM AEDT