When the total nitrogen requirement is furnished post harvest, before planting, or at time of planting, the nitrogen sits in the ground until the crop is mature enough to utilize it fully. This waiting period increases the opportunity for nitrogen loss; meaning investment lost, plant malnourishment and environmental concerns heightened.
The opportunity for nitrogen loss depends on many factors, including soil type and climate. For instance, in soil types that do not have a clay layer, fertilizer loss is a higher risk because there is less material to hold it in the root zone where it can be used by the plants.
As a general rule, application of the entire fertilizer compliment needed by the crop prior to planting would result in higher crop development early in the season, but dwindling production in the latter part of the season.
If part of the nitrogen treatment is postponed, however, nutrients have a higher probability of being available when the plant needs them. Split-applied nitrogen fertilizer applications, like a side dress operation, can save money while also increasing yield per acre.
For forage crops, like corn, split applied nitrogen is absolutely necessary if one wants to keep the plant producing at its highest level throughout the growing season.