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

List of Figures
Figure 2.1 The microbial production of NO and N2O during nitrification ...........................................6
Figure 2.2 The microbial production of NO and N2O during denitrification........................................6
Figure 2.3 Transformation of mineral N in soil (From Wrage et al.(2001)).........................................7
Figure 2.4 The effect of soil available NH4 + and NO3 - on the NO flux. (from (Skiba et al., 1992).....10
Figure 3.1 Schematic of the internal structure of the LMA-3D. .........................................................16
Figure 3.2 Schematic of the calibration procedure carried out for LMA-3D......................................18
Figure 3.3 Calibration curve for NO using LMA-3D instrument .......................................................18
Figure 3.4 Calibration curve for NO2 using LMA-3D instrument......................................................19
Figure 3.5 Example of NO concentration readings taken during the field experiment from a
chamber. ............................................................................................................................21
Figure 4.1 Mean soil NH4 + -N concentrations over time for the non-urine soil (pH 5.2) and the
urine treated soils with varying initial pH values (n = 3, error bars are ± the s.e.m).........30
Figure 4.2 Mesh plot of soil NH4 + -N concentrations over time versus initial soil pH for the urine
treated soils........................................................................................................................31
Figure 4.3 Mean soil NO2 - -N concentrations over time for the non-urine soil (pH 5.2) and the
urine treated soils with varying initial pH values (n = 3, error bars are ± the s.e.m.)........32
Figure 4.4 Mesh plot of soil NO2 - -N concentrations over time versus initial soil pH for the urine
treated soils........................................................................................................................32
Figure 4.5 Soil NO3 - -N concentrations over time for the non-urine soil (pH 5.2) and the urine
treated soils with varying initial pH values (n = 3, error bars are ± the s.e.m)..................36
Figure 4.6 Mesh plot of soil NO3 - -N concentrations over time versus initial soil pH for the urine
treated soils........................................................................................................................37
Figure 4.7 Net NH4 + -N depletion and net NO3 - -N accumulation (ng g -1 soil h -1 ) in urine affected
soil as influenced by initial soil pH treatments. (n = 15, number of samples used for
each individual pH calculation).........................................................................................38
Figure 4.8 Soil NH4 + -N: NO3 - -N ratios over time for the non-urine treated soil (pH 5.2) and the
urine treated soils with varying initial pH values (n = 3, error bars are ± the s.e.m.)........39
Figure 4.9 Soil surface pH after urine application over the experimental time. (n = 3, error bars
are ± the s.e.m.)..................................................................................................................40
Figure 4.10 Mesh plot of soil surface pH versus time and initial soil pH for the urine treated soils....41
Figure 4.11 Calculated HNO2 concentration in urine treated soil over time with varying initial soil
pH treatments (n = 3, error bars are ± the s.e.m). ..............................................................42
Figure 4.12 Mean NO-N flux over time for the non-urine treated soil (pH 5.2) and the urine treated
soils with varying initial soil pH values (n = 3, error bars are ± the s.e.m).......................43
Figure 4.13 Mesh plot of mean NO-N flux versus time and initial soil pH for the urine treated
soils....................................................................................................................................44
Figure 4.14 Cumulative NO-N emitted over time as a % of urine-N applied for the non-urine
treated soil (pH 5.2) and the urine treated soils with varying initial pH values (n = 3,
error bars are ± the s.e.m.). ................................................................................................45
Figure 4.15 Cumulative NO-N flux as a % of urine-N applied after 35 days versus the initial soil
pH. (n = 3, error bars are ± s.e.m)......................................................................................45
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