When exactly should I do top dressing of nitrogen in my crop?

The idea of top dressing is to give nitrogen when the crop is actively growing and can actually use it, instead of dumping it all at sowing where much gets lost. The exact stages depend on the crop, but the general rule is: a starter portion of nitrogen at or near sowing, then the remaining nitrogen in 1 or 2 top dressings during the main vegetative growth and just before the crop's heavy demand stage (for example, tillering and panicle or grain formation in cereals). Each top dressing works best when applied to moist soil or just before an irrigation so the nitrogen moves to the roots, and in the cool hours of the day to reduce loss. Avoid top dressing right before heavy rain that could wash it away, and avoid applying very late when the crop is almost done, as it does little except delay maturity. For the precise stage and split for your specific crop, follow your KVK schedule, and match the total nitrogen to your Soil Health Card or soil test without over-applying.