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

NH 4 + -N (g g -1 dry soil)
1000
800
600
400
200
0
35
30
25
20
15
Days
10
5
0
4.5
5.0
5.5
6.0
6.5
7.0
7.5
Initial soil pH
Figure 4.2 Mesh plot of soil NH4 + -N concentrations over time versus initial soil pH for the
urine treated soils.
4.3.2 Soil NO2 - -N concentrations
Without urine application, mean soil NO2 - -N concentrations ranged from 0.93 to 2.39 µg
g -1 dry soil while in the urine treated soils they ranged from 0.79 to 3.56 µg g -1 dry soil. The
initial soil pH had no significant effect on soil NO2 - -N concentrations (P = 0.15) at day 7, but
on days 14 and 21 higher NO2 - -N concentrations occurred at soil pH 7.6 with no significant
differences among the other treatments (Fig. 4.3). With sampling time as a factor, soil NO2 - -N
concentrations decreased significantly as time progressed (r = -0.64, P < 0.01) (Fig. 4.2).
There was no interaction between initial soil pH treatment and time (P = 0.69) (Fig. 4.4).
When data from all sampling dates were pooled soil NO2 - -N concentrations correlated with
soil NH4 + -N concentrations (r = 0.43, P < 0.01) but the only correlation between these two
variables at any individual sampling day occurred on day 21 (Table, 4.3-4.6) .
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