Factors affecting nitric oxide and nitrous oxide emissions from ...

4.3.8.1 Net NH 4 + -N depletion and NOx fluxes.................................................................................................46
4.3.9 N2O fluxes...................................................................................................................................... 50
4.3.9.1 Net NH 4 + -N depletion and N2O fluxes between up until day 14. .........................................................53
4.3.10 N2O-N: NO-N Ratio .................................................................................................................. 55
4.3.11 WFPS ........................................................................................................................................ 57
4.4 REGRESSION ANALYSIS ....................................................................................................................... 58
4.4.1 Prediction of NO-N fluxes. ............................................................................................................ 58
4.4.2 Prediction of N2O-N ...................................................................................................................... 60
4.5 DISCUSSION ........................................................................................................................................ 61
4.5.1 Inorganic-N transformations and changes in soil pH ................................................................... 61
4.5.2 HNO2 concentrations..................................................................................................................... 62
4.5.3 NO-N and N2O-N fluxes until day 11............................................................................................. 62
4.5.4 NO-N fluxes at initial pH 4.4......................................................................................................... 64
4.5.5 NO-N and N2O-N fluxes after day 11 ............................................................................................ 65
4.5.6 Cumulative NO-N and N2O-N fluxes ............................................................................................. 66
4.5.7 Regression analysis ....................................................................................................................... 67
4.6 CONCLUSIONS..................................................................................................................................... 67
Chapter 5 Effects of moisture and temperature on NOx and N2O gases emissions from bovine urine
applied to soil cores. ............................................................................................................................................ 69
5.1 RATIONALE ......................................................................................................................................... 69
5.2 MATERIALS AND METHODS ................................................................................................................ 70
5.2.1 Treatments and Experimental Design............................................................................................ 70
5.2.2 Sampling protocols and data analysis........................................................................................... 70
5.3 RESULTS ............................................................................................................................................. 71
5.3.1 Soil NH4 + -N concentrations........................................................................................................... 71
5.3.2 Soil NO2 - -N concentrations........................................................................................................... 75
5.3.3 Soil NO3 - -N concentrations........................................................................................................... 82
5.3.4 Net NH4 + -N depletion and NO3 - -N accumulation rates ................................................................ 85
5.3.5 Soil NH4 + -N: NO3 - -N ratio........................................................................................................... 87
5.3.6 Soil surface pH .............................................................................................................................. 89
5.3.7 Theoretical HNO2 concentrations ................................................................................................. 91
5.3.8 NOx fluxes...................................................................................................................................... 93
5.3.8.1 Relationship between soil temperature and NO-N fluxes.....................................................................97
5.3.8.2 Net NH 4 + -N depletion and NOx fluxes.................................................................................................99
5.3.9 N2O fluxes.................................................................................................................................... 101
5.3.9.1 Relationship between soil temperature and N 2O-N fluxes .................................................................109
5.3.10 N2O-N: NO-N ratio.................................................................................................................111
5.3.11 Water-Filled Pore Spaces (WFPS) ......................................................................................... 113
5.4 REGRESSION ANALYSIS ..................................................................................................................... 115
5.4.1 Prediction of NO-N fluxes ........................................................................................................... 115
5.4.2 N2O regression analysis .............................................................................................................. 121
5.5 DISCUSSION ...................................................................................................................................... 125
5.5.1 Soil inorganic-N and pH dynamics.............................................................................................. 125
5.5.2 Theoretical HNO2 and NO fluxes. ............................................................................................... 126
5.5.3 N2O-N fluxes and N2O: NO-N ratios. .......................................................................................... 131
5.6 CONCLUSIONS................................................................................................................................... 132
Chapter 6 Effects of urine-N application rates on NOx and N2O gases emissions under controlled
conditions ........................................................................................................................................................... 135
6.1 RATIONALE ....................................................................................................................................... 135
6.2 MATERIALS AND METHODS ............................................................................................................... 135
6.2.1 Treatments and Experimental Design.......................................................................................... 135
6.2.2 Soil sampling and Analysis.......................................................................................................... 136
6.2.3 N2O and NOx sampling and analyses .......................................................................................... 136
6.2.4 Statistical Analysis....................................................................................................................... 136
6.3 RESULTS ........................................................................................................................................... 137
6.3.1 Soil NH4 + -N concentrations......................................................................................................... 137
6.3.2 Soil NO2 - -N concentrations.......................................................................................................... 138
6.3.3 Soil NO3 - -N concentrations.......................................................................................................... 139
6.3.4 Net NH4 + -N depletion and NO3 - -N accumulation rates .............................................................. 142
6.3.5 Soil pH......................................................................................................................................... 143
6.3.6 Theoretical HNO2 concentrations ............................................................................................... 145
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