Doctor of Philosophy (PhD)


Plant, Enviromental and Soil Sciences

Document Type



Application of N fertilizers and special land management practices during agricultural production could have significant implication in influencing the air quality. In this study, field experiments were established at different research sites in Louisiana to evaluate the emission of ammonia (NH3), greenhouse gases (GHG), and fine particulates from sugarcane cultivation and harvesting. Specifically, this study was planned to (i) evaluate the effect of different N sources (urea and urea ammonium nitrate) and residue management schemes (residue burned, RB; and residue retained, RR) on NH3 and GHG emissions, (ii) characterize the chemical and morphological characteristics of fine particles generated during sugarcane harvesting operations (regular harvesting, RH; ground burn, GB; standing burn, SB; and combine harvesting, CH), and (iii) evaluate the micrometeorological study of NH3 flux above sugarcane crop canopy. Ammonia (NH3) and greenhouse gas samples were collected through active and passive chamber methods, respectively, following N application in the field. Then those NH3 and GHG samples were analyzed using ion chromatography (IC) and gas chromatography, respectively. Organic/elemental carbon, water soluble species, elemental species, and morphological features were determined using thermal carbon analyzer, ion chromatography, inductively-coupled plasma-optical emission spectroscopy, and scanning electron microscopy, respectively. Volatile organic carbon and polycyclic aromatic hydrocarbons were analyzed using gas chromatography-mass spectroscopy. Bi-directional NH3 emission was obtained from two installed denuders (at 10 ft and 18 ft) equipped with meteorological tower in the sugarcane field and the captured NH3 was analyzed in IC. Field experiments showed that urea treatment produced almost 2.8 times and 1.6 times higher NH3 and N2O, respectively, as compared to UAN plots. However, N had little effect on CH4 and N2O emissions. Overall, majority of total NH3 and N2O emission was observed within 3-4 weeks after N application in the field. On the other hand, residue retained treatment resulted significantly higher NH3, N2O, and CH4 emissions as compared to RB treatments over the years. Ammonia and N2O emissions were highly correlated with water filled pore space (%), but higher correlation was found in 2012 due to higher rainfall received within 3 weeks of N application. Particulates released during different sugarcane harvesting operations showed that carbonaceous compounds contributed about 30-70% of the total particle mass. Ammonia was the major cation found in the burning particulates (GB and SB) and showed high correlation with SO42- ions. Overall, organic carbon, major ionic species, elemental species were significantly higher in GB particles than SB particles. Low molecular weight polycyclic aromatic hydrocarbons were mainly released during sugarcane residue burning operations. Molar ratio of standing burn smoke samples was found lower than ground burn samples over four years. Ammonia emission above sugarcane crop canopy was highly dependable on different meteorological parameters such as temperature, rainfall, and wind speed. Major NH3 emission peaks were found during heavy rainfall days combined with favorable temperature. Higher rainfall increased anaerobic soil conditions and thus released more NH3 from soil surface. Daytime NH3 emission was significantly higher than nighttime emission because of higher temperature during day which helps in NH3 volatilization both from soil and crop surface. Higher wind speed created turbulence in atmospheric boundary layer and thus helped more NH3 emissions. Overall, these results are useful in managing sugarcane production while minimizing NH3, GHG and particle matter emissions.



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Committee Chair

Wang, Jim Jian