This is also true of pea varieties. You may still need to spray the taller varieties, but your weed control will be better because of the added crop competition. Wheat and peas are generally sown as early as possible, while crops like canola are planted later to avoid spring frosts. Wild oats can quickly become a serious problem on early-sown fields that are in continuous wheat production. Changing the seeding date from year to year means that specific types of weeds cannot adapt.
Crops differ in their competitive ability .
Wheat, barley and canola are more competitive than flax or pulse crops. Varying the life cycle of the crops you grow will help prevent weeds from adapting. Using crops with different life cycles will help prevent weeds with specific life cycles from adapting and establishing. Economic thresholds can help you decide if it is necessary to spray weeds, allowing you to save money on your herbicide bill. Economic thresholds make use of yield loss equations that allow you to determine how much yield you stand to lose at a given weed density.