Sidedressing N can be done in different ways and with different sources of N, yet the concept of applying fertilizer after corn emergence is consistent. This strategy includes applying N during plant uptake, as well as timing the application to reduce the risk of loss from early spring rainfall and leaching events. For this practice, sidedressing is considered only as early sidedress timing (corn height below 24-inch) or application based on soil nitrate sampling.
The research summary showed an average 5% reduction in nitrate-N concentration in tile drainage water when moving from fall to spring/split-applied nitrogen fertilizer, and 4-7% reduction with sidedress compared to spring pre-plant, considering the same application rate. Sidedressing also allows the N rate to be optimized by either soil sampling or crop canopy sensing.