Nitrogen Uptake and Partitioning Lessons Learned from Pulse-Labeled 15N Applications to Field-Grown Corn.

Efforts have been made in numerous studies to better understand N dynamics to increase corn yields and N efficiency, but most often it is not possible to separate the uptake of indigenous soil- versus fertilizer-derived N over time. The approach of using a “pulse-labeled N” technique provides potentially more accurate information about the fate of the most recent N uptake and partitioning into the plant. Therefore, we investigated the application of labelled Ca¹⁵(NO₃)₂  into the root zone of different genotypes at multiple development stages and two N rates in two field environments in 2013. The supplemental ¹⁵N application followed “check” versus “moderate” N rates applied at sidedress time. We separated, dried and analyzed plant components 4 to 5 days after the labelled N application, and determined the concentration of ¹⁵N present in each component.  This method successfully provided precise estimations of the newest N uptake and allocation to corn plant components at each growth stage.  This technique, or modifications of it, are potentially useful for better understanding basic mechanisms differentiating genotypes that are high versus low in overall N use efficiency.