Degree Type


Date of Award


Degree Name

Master of Science




Crop Production and Physiology

First Advisor

Jode W Edwards


Studies on economic optimum nitrogen rate (EONR) for corn have largely ignored interactions with plant density and hybrid. Typically, the EONR is determined by fitting a quadratic-plus-plateau model to the observed data. This study provides a novel model of a logistic function of nitrogen where the shape of the function is modified by nitrogen interactions with density. We set up a comprehensive factorial experiment (5 plant densities x 5 nitrogen rate x 4 hybrids x 2 replications x 2 environmental) to generate data to build the new framework. The coupled density by nitrogen surface response models captured 92% of the variability in the observed grain yield with a normalized root mean square error of 7%. Results indicated that EONR response to density was quadratic with variation in response among hybrids. This study showed that increases in plant density increased nitrogen use efficiency (NUE: (Yield at opt N – Yield at zero N)/EONR) from 11 to 37 kg dry matter per kg N applied, and this result was consistent for all hybrids. Plant density increased time to anthesis and anthesis to silking interval by delaying silk emergence across all hybrids. In conclusion, this is the first study that models the interaction of the logistic response of nitrogen that incorporates the effects of density and nitrogen together in a single model.


Copyright Owner

Kyle King



File Format


File Size

52 pages