Is foliar feeding a good way to fix a hungry crop fast, or should I stick to soil application?

Foliar feeding (spraying nutrients on the leaves) is a useful tool but it is a top-up, not a substitute for the main soil-applied fertiliser. The leaves can only absorb small quantities at a time, so foliar sprays are best for quick correction of a specific deficiency, for micronutrients like zinc or iron, and for giving the crop a short boost at a critical stage. They cannot supply the large bulk quantities of nitrogen, phosphorus and potash that the crop needs over the whole season; that has to come from the soil through the roots. So foliar feeding makes the most sense when: the soil cannot deliver a nutrient fast enough (for example iron or zinc on problem soils), the crop shows a clear deficiency you need to fix quickly, or the roots are temporarily stressed. For routine bulk nutrition, soil application remains the base. Spray in the cool hours with a fine nozzle for good coverage, at the rate on the label, and not before rain. Confirm what is actually deficient before spraying rather than spraying blindly. Follow the product label and your KVK advice, base the overall plan on your Soil Health Card or soil test, and do not over-apply.