To meet nitrogen level needs while avoiding weather-related pitfalls, growers should consider applying nitrogen (N) at multiple times. N may be applied in the fall, early spring (preplant), at planting and in-season (sidedress).
"The ideal circumstances are to do a split application," says John Shanahan, Pioneer Hi-Bred agronomy research manager.
This time of year — in-season — N applications allow for adjustments to planned nitrogen supply based on weather variations.
If wet spring conditions result in N losses, sidedress rates can be increased. If warm temperatures and moderate rainfall results in high N mineralization and an N-sufficient crop, sidedress rates can be reduced. (Determining these needs can be done using these evaluation tools.)
In-season N applications can supply nitrogen to the crop near the time of maximum plant uptake. However, if wet conditions develop, sidedress applications may be delayed beyond the optimum application date. Very dry conditions can result in a delay in availability of sidedressed N to the plant.
Because of the risks associated with in-season nitrogen application, the practice should be managed carefully. Soil fertility specialists often recommend only 1/3 of total crop supply be targeted for sidedress application. In addition, growers should be prepared to apply sidedress N as quickly as possible when the window of opportunity appears. Finally, a backup plan should be in place for in-season application to help avert significant N deficiency and yield loss in case of weather issues.
"To make the most of nitrogen applications, growers need to evaluate the type of equipment and nitrogen sources available," Shanahan says. "They also need to assess the weather and adjust based on conditions to ensure an nitrogen strategy that delivers."