With wind delays and pressure to get crops seeded, the weed spraying operation could be bouncing from crop to crop, and from pre-seed burnoff in one field to early post-emergence in another. This requires extra attention to detail for tank mixing and sprayer clean-out.
It is always good practice to clean the sprayer, especially between pre-seed and in-crop applications. Pre-seed burnoff programs often include three or four active ingredients, including Group 2 and Group 14 products ahead of cereal crops. You want to make sure these Group 2 and 14 products are completely cleaned from the sprayer tank, plumbing and nozzles before spraying canola.
Also, common canola-crop herbicides and surfactants left in a tank for any extended period of time are very good at removing these residue deposits from tank walls and sprayer plumbing, causing them to mix in with the spray solution. If wind or rain delays spraying, the concentration of scrubbed-free herbicide residue in the tank and booms can continue to increase.
This underlines the importance of a complete clean-out between products, and of an understanding of what risks each product and each tank mix presents. Read Sprayer tank clean-out tips for specific steps and some good links