1. DEPARTMENT OF
PRIMARY INDUSTRIES
Can we reduce nitrous oxide emissions from
crops?
Sally J. Officer, Gavin Kearney, Frances Phillips, Roger Armstrong and
Kevin Kelly.
N2O
Network

2. Atmospheric nitrous
oxide is increasing
in the same “hockey
stick” pattern as
carbon dioxide and
methane.
Atmospheric gas
concentrations over
the past 1000 years

3. 84% of nitrous oxide emissions come
from agriculture in Australia.
75% of this nitrous oxide is
generated by micro-
organisms in agricultural soil,
using N derived from:-
•Nitrogen fertilizer
•Soil disturbance
•Animals

4. “66% of nitrogen fertiliser is used on
cereals in Australia.”
Additional slide to be used at your
“90% of the
discretion increase in N2O emissions
from 1990 to 1999 was due to an increase
in the rate of N fertiliser application”
(Dalal as soil reaches saturation. DCD may now be
Very large increase in emissions in July
et al, 2003)
ineffective, but we will not be sure until statistical modelling is completed.

5. Measuring N2O emissions from fertilised crops
TGA
Automated chamber system
measuring nitrous oxide 16
times a day

6. Comparison of emissions from wheat cropping soils
with either N fertiliser or a legume rotation as the source
of N

7. Rainfall during emissions monitoring
80
70 Annual rain
60
Rainfall (mm) 50 372 mm
40
2007 30
20 GSR rain
10
0 205 mm
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Decile 2
Drought years, good indicators of future conditions
80
Annual rain
70
60 322 mm
Rainfall (mm)
50
2008 40
30
20 GSR rain
10
0
183 mm
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Decile 1

8. Daily average emissions and soil moisture 2007
12 50
Sowing Harvest
45
10
40
Soil moisture content (v/v%)
2007
Increased Flux in 2007
35
Flux N2O (g N.ha-1.d-1)
8 300
250 30
200
6 64% 23% 25
g/ha
150
A marked increase in N2O flux from cultivated plots immediately after cultivation and
20
100
planting. Possible early effect of the DCD (need statistical analysis.
4
15
50
0 10
2 No N fertiliser 50 kg N/ha 50 kg N/ha
5
0 0
Apr-2007 Jun-2007 Aug-2007 Oct-2007 Dec-2007 Jan-2008
Wheat, No N fertiliser Wheat and N fertiliser
Wheat and N fertiliser and irrigation Soil water

9. Daily average emissions and soil moisture 2008
Sowing Harvest
Increased flux in 2008
160
140
120
100
84%
g/ha
80
60 154%
40
20
0
No N fertiliser No N fertiliser 50 kg N/ha

10. Soil mechanisms
O2
Nitrification
NH4+ CO2
cycle
N 2O N2O
(aerobic)
NO3-

11. Soil mechanisms
O2
Nitrification
NH4+ CO2
cycle
N 2O N2O
(aerobic)
NO3-
NO-
N2 N2
Denitrification NO3- N2
cycle
(anaerobic)
NO2- N2O N 2O
NO

12. O2
NH4+ CO2
N 2O N2O
NO3-
NO-
The application of band of concentrated urea N2
N2 granules to
NO3- N
an aerobic (drained) soil 2causes large losses of nitrous
oxideNO2-
through N2O nitrification pathway
the
NO

13. 1) A clear increase in
nitrous oxide emissions
associated with the use
of urea
2) No yield advantage
from urea in two
relatively dry years
3) Legume rotations
supplied sufficient N for
semiarid wheat under
low rainfall and also
generated less nitrous
oxide

14. Can the humble
legume help to save
the planet?

15. Legumes can be difficult to establish and may not grow well
in drier years, while a year of more reliable non leguminous
grain crop has been lost.
Nevertheless, encouraging farmers to increase their use of
legume rotations should reduce emissions from Australian
grain crops.