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In contrast, on the arable reversion grassland plots nitrate concentrations in drainage
waters were low and generally below the EC limit throughout the drainage season.
On these plots, there was no effect (P>0.05) of slurry application timing (Figure 1b)
on drainage water nitrate concentrations.
a. Arable
b. Grassland
140
140
120
120
Nitrate-N concentration (mg/l)
100
80
60
40
20
Autumn
Winter
Spring
EC limit 11.3 mg/l NO 3 -N
Nitrate-N concentration (mg/l)
100
80
60
40
20
E C limit 11.3 mg/l NO3-N
Autumn
Winter
Spring
0
20-Nov-03 09-Jan-04 28-Feb-04 18-Apr-04
Date
0
20-Nov-03 09-Jan-04 28-Feb-04 18-Apr-04
Date
Figure 1: Mean nitrate-N concentrations in drainage water at Brimstone Farm
(2003/04)
The autumn and winter slurry applications had no effect on ammonium-N
concentrations in drainage waters from either the arable or grass plots. In both
instances, these remained below the EC Freshwater Fish Directive limit of 0.78 mg/L
NH 4
-N throughout the drainage season (Figure 2a and b). However, after the spring
slurry application timing, when c. 20 mm of rain fell 9–12 days after the slurry was
applied, ammonium-N concentrations peaked at 4.5 and 3.9 mg/L NH 4
-N on the
grassland and arable plots, respectively. These measurements suggest that the
rainfall soon after application had caused slurry nitrogen to move rapidly through the
soil profile, via macropores (‘by-pass’ flow), to the drains.
a. Arable
5
b. Grassland
5
Ammonium-N concentration (mg/l)
4
3
2
1
FFD limit 0.78 mg/l NH4-N
Autumn
Winter
Spring
Ammonium-N concentration (mg/l)
4
3
2
1
FFD limit 0.78 mg/l NH4-N
Autumn
Winter
Spring
0
20-Nov-03 09-Jan-04 28-Feb-04 18-Apr-04
Date
0
20-Nov-03 09-Jan-04 28-Feb-04 18-Apr-04
Date
Figure 2: Mean ammonium-N concentrations in drainage water at Brimstone
Farm (2003/04)
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