Canola in fields with excess moisture will often show various signs of stress, including yellowing, purpling, stunted growth — or all of three. Excess moisture creates two problems for crop nutrition: (1) It can remove nutrient from the soil. And (2) it can “drown” roots and make it impossible for them to take up nutrients — even if nutrients are present in ample quantities.
The best practice in this case is to wait and see how well the crop recovers before investing in a nutrient top dress. Crop stressed by excess moisture may not recover strongly after the soil dries out and therefore may not benefit, financially, from a top dress of nutrients. If the decision is made to top dress a field, top dress could be targeted to higher ground where plants are healthiest and a return on investment is most likely.