Agronomy and Horticulture Department


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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 Charles S. Wortmann. Lincoln, Nebraska: August, 2013

Copyright (c) 2013 Blythe Patience McAfee


A range of flux chambers are available and have been used to measure fluxes of atmospheric gases, including NH3, with the addition of acid traps. Previous studies show acid traps can be very effective but there is a need to understand how chambers affect acid trap efficiency so measurements can be adjusted for more accurate results. In this lab study, chamber tightness, pump flow variation, and NH3 trapping efficiency of a flux chamber system were examined. Chamber leakage varied with time from 1-7%. Pumping rate between pumps was significantly different and when included in the closed chamber system, pump rate was reduced on average by 43.8 ± 0.598%. Compared to the acid bubbler trap alone (Woodbury et al., 2006), the trapping efficiency of the acid trap-chamber system was lower and varied with the mass of NH3 emitted. Chamber tightness and pump flow rate also contribute to overall chamber efficiency, with pump flow rate having the greatest effect of all parameters examined. These findings were used to improve a mass-based model for calculating NH3 trapping efficiency of the system. The model predicts the mass and percentage of NH3 collected from the flux chamber system based on the varying of different chamber input parameters. The model can be used to estimate trapping efficiency of chambers, or be used to calculate and adjust previous NH3 measurements taken with this closed flux chamber system. The model was utilized to estimate NH3 fluxes from the following study on sprinkler application of beef feedlot effluent.

Loss of nitrogen from sprinkler applied beef feedlot effluent can be costly for both the producer and the environment. Sprinkler application of effluent is common throughout the Great Plains, though little work has occurred focusing specifically on N losses from beef feedlot effluent. The objectives of two studies were to quantify NH3 and N2O losses from beef feedlot effluent applications under field conditions and determine the effects of soil pH, percent water filled pore space, NH4+ concentration of the effluent, and weather conditions on NH3and N2O. Nitrogen losses during application were determined from the differences between NH4+-N concentration of samples taken under the sprinklers and samples taken from the effluent. NH3-N and N2O emission following application were measured using a closed chamber technique with a recirculating configuration and acid traps. In the first study, sprinklers were protected from the wind and NH4+-N losses[1] during application were not seen. Average rate losses from a second study, with no protection against wind and a mean wind speed of 15 m s-1, accounted for 55% of the effluent NH4+-N from drift beyond collection jars during sprinkler application. Following application, N losses from both volatilization and N2O emissions from soil were less than[2]1% of the original effluent NH4+-N concentration. Soil pH and effluent NH4+-N concentration did not significantly affect the percent of N lost. Increasing wind speed and air temperature resulted in greater N losses during application. Weather factors including: soil temperature, air temperature, %WFPS, and relative humidity had varying effects on NH3 and N2O emissions following application.

Advisor: Charles S. Wortmann

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