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

McKenney & Drury (1997) found high NOx emissions 1.19 to 44 ng N m -2 s -1 from fertilized
soil. Significant positive correlation of NOx emissions with both NH4 + -N (Hutchinson &
Brams, 1992; Smart et al., 1999) and NO3 - - N substrates e.g. (Williams & Fehsenfeld, 1991;
Williams et al., 1998) have been reported. Similarly, Skiba et al. (1992) also found a positive
relationship between NO and N2O emissions and the total soil inorganic-N pool (Fig. 2.4).
Shepherd et al. (1991) and Veldkamp & Keller (1997) reported 5-10 % of fertilizer-N was lost
as NOx when applied to agriculture soils. The correlation of NOx emission with N rate may be
of significance when considering the rate of N deposited on a urine patch, which is about
1000 kg N ha -1 or 10 times greater than an artificial fertiliser dose such as urea which is
applied usually at a rate < 100 kg N ha -1 . There appears to have been only one laboratory
study where, NOx fluxes have been measured as a consequence of varying urine-N rate
applied to soil. This study (Clough et al., 2003c) used SIFT-MS to examine the effect of
varying rates of synthetic urine application on nitrogen oxides (NO + NO2) and ammonia
emissions. The amount of urine-N applied, emitted as NO-N was 6.6, 2.4, 3.8 and 0.2% at
100, 250, 500 and 1000 kg urine-N ha -1 .
Figure 2.4 The effect of soil available NH4 + and NO3 - on the NO flux. (from (Skiba et al.,
1992).
2.6.2 Soil pH
Stehfest & Bouwman (2006) summarized over 1200 measurements of N2O from agricultural
fields and natural vegetation and concluded that soil pH significantly influenced N2O
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