Time and Rate of Urea Application Influence Corn Yield and Nitrogen Use Efficiency.

The timing and rate of fertilizer N application can influence corn (Zea mays L.) grain yield and soil fertility. Experiments were conducted in 2014 and 2015 to compare single and split applications for differing rates of fertilizer N on an irrigated Hubbard-Mosford loamy sand complex at Becker, MN and under non-irrigated conditions on a Normania loam soil at Lamberton, MN and on a Nicollet clay loam soil at Waseca, MN. A full (100%) rate of N applied as a three-way split application (before planting, at the six leaf collar (V6) corn stage, and at silking) produced greater grain yield than all other rates and timings of fertilizer N application at Becker in 2014, while a traditional split application (before planting and at V6 corn stage) produced greater grain yield in 2015. Conversely, the application of 125% N rate applied before planting produced greater yield than all other treatments at Waseca in 2014 while the application of 100% N rate applied as a split application produced greater yield in 2015. There were no differences in grain yield due to rate or timing of fertilizer N application when N was applied at Lamberton in 2014 or 2015. These results demonstrate that split-applications of N can increase corn grain yield on irrigated coarse-textured soils and on non-irrigated clay loam soils. Findings also suggest that split N applications can improve soil N levels later in the season. Enhanced understanding of site-specific soil and weather characteristics that influence such responses could increase corn yield and N uptake while reducing the potential for N losses to the environment.