can we reduce nitrous oxide emissions from crops? - sally officer
TRANSCRIPT
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
Atmospheric gas concentrations over the past 1000 years
Atmospheric nitrous oxide is increasing in the same “hockey stick” pattern as carbon dioxide and methane.
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
Additional slide to be used at your discretion
Very large increase in emissions in July as soil reaches saturation. DCD may now be ineffective, but we will not be sure until statistical modelling is completed.
“66% of nitrogen fertiliser is used on cereals in Australia.”
“90% of the increase in N2O emissions from 1990 to 1999 was due to an increase in the rate of N fertiliser application” (Dalal et al,
2003)
TGA
Measuring N2O emissions from fertilised
crops
Automated chamber system measuring nitrous
oxide 16 times a day
Comparison of emissions from wheat cropping soils with either N fertiliser or a legume
rotation as the source of N
01020304050607080
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Rai
nfa
ll (
mm
)
01020304050607080
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Rai
nfa
ll (
mm
)
2007
2008
Rainfall during emissions monitoring
Annual rain
372 mm
GSR rain
205 mm
Decile 2
Annual rain
322 mm
GSR rain
183 mm
Decile 1
Drought years, good indicators of future conditions
A marked increase in N2O flux from cultivated plots immediately after
cultivation and planting. Possible early effect of the DCD (need statistical analysis.
Daily average emissions and soil moisture 2007
0
2
4
6
8
10
12
Apr-2007 Jun-2007 Aug-2007 Oct-2007 Dec-2007 Jan-2008
Flu
x N
2 O (
g N
.ha-1
.d-1
)
0
5
10
15
20
25
30
35
40
45
50
So
il m
ois
ture
co
nte
nt
(v/v
%)
Wheat, No N fertiliser Wheat and N fertiliser
Wheat and N fertiliser and irrigation Soil water
Sowing Harvest
0
50
100
150
200
250
300
No N fertiliser 50 kg N/ha 50 kg N/ha
g/ha
2007Increased Flux in 2007
23%64%
Daily average emissions and soil moisture 2008
Sowing Harvest
0
20
40
60
80
100
120
140
160
No N fertiliser No N fertiliser 50 kg N/hag/
ha
Increased flux in 2008
84%154%
O2
CO2NH4+
NO3-
N2ON2O
Nitrification cycle
(aerobic)
Soil mechanisms
NO-
O2
CO2NH4+
NO3-
N2 N2
NO
NO3-
NO2- N2O
N2
N2ON2O
N2O
Nitrification cycle
(aerobic)
Denitrification cycle
(anaerobic)
Soil mechanisms
NO-
O2
CO2NH4+
NO3-
N2 N2
NO
NO3-
NO2- N2O
N2
N2ON2O
The application of band of concentrated urea granules to an aerobic (drained) soil causes large
losses of nitrous oxide through the nitrification pathway
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
Can the humble legume help to save the planet?
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.