The Pioneer web site has as interesting review on nitrogen fertilizer use in corn. It covers the key issues of why nitrogen is important and how the corn's need is nitrogen is heaviest from V8 or knee-high until tassel. Yet getting the N to the plant is the trick. After talking about the various application methods, the site then states:
"The effect on yield of N application timing has been widely studied for decades. Common types of nitrogen timing studies include applications in the fall vs. spring (preplant), preplant vs. split between preplant and sidedress, and different types of N fertilizers applied at various timings. Other studies also tested N application timing, multiple rates of N, and different proportions of total N applied at various times. These studies show a wide range of results that often vary according to the weather conditions encountered during the study. For this reason, understanding the relationship between N supply, weather conditions, and corn needs is more important to developing successful N management strategies than research results per se."
And their summary: "Applying N at multiple times, including the time of maximum crop uptake, is a good way to spread risks and reduce costs, but the extent to which this is practical depends on prevailing weather conditions in your area. Historical weather data can be used to determine how much applied N may be lost in typical months, and also to indicate how many days may be available for field work when sidedress applications need to be made."
"Using historic weather information, growers should develop an N-timing strategy with a high probability of implementation most years. Such strategies should be weighted heavily for soil type and topography, which impact retention of applied N and the ability to apply additional N. Regions and individual fields vary in those properties, so many growers should have multiple N-management strategies in their farming operation. In addition, growers must be ready to implement a "plan B", when excessive or prolonged rainfall disrupts original plans."
Yes, it all comes back to management. But the read is a good review to be sure you're hitting all the key points in your nitrogen management program.
Link to the full article: