Agronomy and Horticulture Department


Date of this Version

Summer 7-29-2011


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 Professor Richard Ferguson. Lincoln, Nebraska: July, 2011

Copyright 2011 Brian Theodore Krienke


Nitrogen fertilizer is frequently the most limiting nutrient in corn production. Typically most nitrogen is applied before planting. Since nitrogen can leave the soil system fairly easily, the result can be an inefficient use of nitrogen fertilizer. Previous research has shown increased efficiency with no reduction in yield by applying nitrogen later in the season when the crop is actively growing, with rates regulated spatially through the use of active crop canopy sensors. This study evaluated the potential for N cutoff thresholds using a sufficiency index as the threshold value for areas with poor stand or an unrecoverable N deficiency. In this study the algorithm developed by Solari, et al. (2010) was used. Field scale treatments were imposed on six irrigated fields in south-central and western Nebraska to evaluate performance of the active crop canopy sensor-based in-season N management algorithm with and without predicted permanent yield loss thresholds. The study found no consistent advantage in yield, nitrogen use efficiency, or profit with sensor-based treatments using algorithm thresholds. The uniform, soil-test-based UNL treatment was most often the most profitable treatment. Further research is needed to revise the Solari, et al. (2010) method to account for soil-N supply prior to and following in-season N application.

Adviser: Richard Ferguson