Agronomy and Horticulture Department


First Advisor

Dr. Javed Iqbal

Second Advisor

Dr. Amit Jhala

Date of this Version



A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Agronomy, Under the Supervision of Professors Javed Iqbal and Amit Jhala. Lincoln, Nebraska: December, 2022

Copyright © 2022 William Neels


Nitrogen fertilizer management continue to be challenging due to potential nitrogen losses under variable weather conditions. The objective of this was to evaluate the performance of nitrification inhibitors, nitrogen sources and herbicides on in-season nitrogen availability and agronomy indicators. A two site-year field experiment was conducted in silty clay loam soil in corn phase of the corn-soybean rotation at Central Nebraska. The treatments included three herbicide (no pre-emergence, Acuron, Resicore) and five nitrogen treatments: 1) control, 2) anhydrous ammonia, 3) anhydrous ammonia without nitrification inhibitor, 4) urea with nitrification inhibitors, and 5) urea without nitrification inhibitors. Results indicated that nitrogen source has a more significant effect on NH4+-N retention (78-80% higher in anhydrous ammonia vs. urea) than nitrification inhibitor (24-47% higher with inhibitor vs. without inhibitor) and herbicides. Similarly, nitrogen source significantly affected NO3--N formation (134-176% lower in anhydrous ammonia vs. urea) than nitrification inhibitor (8-31% lower with inhibitor vs. without inhibitor) and herbicides. Pre-emergence herbicide increased corn grain yield at one site year, while nitrification inhibitors did not affect agronomic indicators. Within nitrogen source, anhydrous ammonia increased grain yield by 1.06 Mg ha-1, partial factor productivity by 5.7 kg grain kg-1 N, agronomic efficiency by 5.5 kg grain kg-1 N, aboveground biomass N uptake by 35 kg N ha-1, grain N uptake by 15 kg N ha-1, nitrogen recovery efficiency by 21% and residual total inorganic N by 6-40 kg N ha-1 compared to urea.

Advisors: Javed Iqbal and Amit Jhala