Options for reducing soil nitrous oxide emissions
in the NSW dryland grains industry Graeme Schwenke (northern NSW)
Guangdi Li (southern NSW) De Li Liu (simulation modelling)
NSW Department of Primary Industries
Acknowledgments Tamworth Agricultural Institute, Wagga Wagga Agricultural Institute,
Liverpool Plains Field Station, Ian Carter Bruce Haigh, Annabelle McPherson, Bill Keene, Peter Sanson, Tara
Burns, Mandy Holland, Wayne McPherson, Kamal Hossain, Helen Squires, Nicole Carrigan, Pete Formann, Jan Hosking, Steve Morphett, Jim Perfrement, Pete Perfrement, Pat Mortell, Matt Gardner, Rick Graham, Steve Kimber, Brad Keen, and Leanne Lisle (UNE).
Adam Lowrie, Richard Lowrie, Graeme Poile, Albert Oates, Binbin Xu, Vince van der Rijt, Sarah Bond and Kare Maihemuti.
John Finlayson, Muhuddin Anwar, Yuchuan Ma, Bin Wang and Changsheng Li, Yong Li, Jianmin Lin.
Peter Grace, Clemens Scheer, Dave Rowlings, Christian Brunk
Project Objectives Compare options that reduce N2O emissions and increase N
use efficiency from northern and southern NSW dryland grains cropping – Options included:
• optimise N rate applied, • split application of fertiliser N, • use of N fertiliser containing inhibitors, • substitution of fertiliser N with legume-derived N
Validation of process-based biogeochemistry models for N2O
emitted from dryland grain cropping trials.
Simulate net greenhouse gas emissions under different agronomic practices using current and projected future climate scenarios
0 kg N/ha 40 kg N/ha
120 kg N/ha 200 kg N/ha
Northern NSW Year 1 – N rate response N2O rate response?
Date
10/12 11/12 12/12 1/13 2/13 3/13 4/13 5/13 6/13 7/13 8/13 9/13 10/13
Cum
ulat
ive
N2O
em
issi
ons
(g N
2O-N
/ha)
0
1000
Date
10/12 11/12 12/12 1/13 2/13 3/13 4/13 5/13 6/13 7/13 8/13 9/13 10/13
Dai
ly ra
infa
ll (m
m)
Vou
met
ric s
oil w
ater
(%)
Ave
rage
tem
pera
ture
(o C)
0
10
20
30
40
50
60
70
80
90
0 kg N/ha
40 kg N/ha120 kg N/ha200 kg N/ha
Northern NSW Year 2 – How to delay soil nitrate availability: nitrification inhibitor or late-apply N?
10/13 11/13 12/13 1/14 2/14 3/14 4/14 5/14 6/14 7/14 8/14 9/14 10/14
Cum
ulat
ive
N2O
em
issi
ons
(g N
2O-N
/ha)
0
100
200
300
400
500
600
700
800
900
1000
1100
1200
Date
10/13 11/13 12/13 1/14 2/14 3/14 4/14 5/14 6/14 7/14 8/14 9/14 10/14
Dai
ly ra
infa
ll (m
m)
Aver
age
tem
pera
ture
(o C)
Volu
met
ric s
oil w
ater
(%)
0
10
20
30
40
50
60
N (sowing)
N (booting) harvest
0 kg N/ha
Urea 100 kg N/ha (sowing)Entec 100 kg N/ha (sowing)Urea 100 kg N/ha (booting)
0
500
1000
1500
2000
2500G
ross
mar
gin
($/h
a)
Tamworth (main site: auto chambers) – Optimise the N fertiliser rate for soil N and expected yield
• Soil N levels determined by previous sorghum (low N) or soybean brown manure (high N)
• +N vs nil N treatments – Split N treatment (33% sowing + 67% booting)
Northern NSW Year 3 – Optimise N and delay nitrate availability.
Year 3 ~ Road-testing options
Cumulative N2O emissions
10/14 11/14 12/14 1/15 2/15 3/15 4/15 5/15 6/15 7/15 8/15 9/15 10/15 C
umul
ativ
e N
2O e
mis
sion
s (g
N2O
-N/h
a)0
100
200
300
400
500
600
Date
10/14 11/14 12/14 1/15 2/15 3/15 4/15 5/15 6/15 7/15 8/15 9/15 10/15
Dai
ly ra
infa
ll (m
m)
Aver
age
tem
pera
ture
(o C)
Volu
met
ric s
oil w
ater
(%)
0
10
20
30
40
50
60
sowing(+N)
harvest (sorg) + 120 kg N/ha
(soy) + 0 kg N/ha
(sorg) + 0 kg N/ha
(soy) + 40 kg N/ha
Growing season rainfall = 422 mm
(longterm = 356 mm)
Grain yields
Breeza (satellite site: manual chambers) – Delay conversion of urea -> nitrate in the soil
• DMPP-coated urea (nitrification inhibitor) [EntecTM] • Polymer coated urea (physical isolation of granule)
– Split N fertiliser (33% sowing + 67% booting)
Northern NSW Year 3 – Optimise N and delay nitrate availability.
Year 3 ~ Road-testing options
Cumulative N2O emissions
10/14 11/14 12/14 1/15 2/15 3/15 4/15 5/15 6/15 7/15 8/15 9/15 10/15
Cum
ulat
ive
N2O
em
issi
ons
(g N
2O-N
/ha)
0
100
200
300
400
500
600
700
800
900
1000
1100
1200
Date
10/14 11/14 12/14 1/15 2/15 3/15 4/15 5/15 6/15 7/15 8/15 9/15 10/15
Dai
ly ra
infa
ll (m
m)
Aver
age
tem
pera
ture
(o C)
Volu
met
ric s
oil w
ater
(%)
0
10
20
30
40
50
60
N (sowing)
N (booting)harvest
0 kg N/ha urea at sowing100% urea at sowing100% entec urea at sowing100% poly urea at sowing
33% urea / 67% entec at sowing33% urea / 67% poly at sowing33% urea / 33% entec / 33% poly at sowing
33% urea at sowing, 67% urea at booting33% entec at sowing, 67% urea at booting33% poly at sowing, 67% urea at booting
33% urea at sowing, 67% NV urea at booting33% entec at sowing, 67% NV urea at booting33% poly at sowing, 67% NV urea at booting
Growing season rainfall = 253 mm
(longterm = 321 mm)
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
1 2 3 4 5 6 7 8 9 10 11 12 13
Gra
in y
ield
(t/
ha)
Treatment number
a
dcd
dbcd
bcd cd
ab
d d cd d
100% urea at sowing
1:3 poly’:urea at sowing
Nil N
100% poly’ urea at sowing
Grain yields
0.000
0.100
0.200
0.300
0.400
0.500
0.600
0.700
0.800
0.900
1.000
2 3 4 5 6 7 8 9 10 11 12 13
Emis
sio
n f
act
or
(%)
a a a a
b
c
d
a aa
abab
Reduction in growing-season N2O emissions compared to urea applied at sowing
Year Chambers EntecTM applied at sowing
Urea applied at booting
2010-11 manual 100% -
2013-14 manual 91-97% 80%
auto 65-81% 81%
2014-15 manual 81% 58-65%
N2O mitigation strategies ~ dryland sorghum
Optimise the amount of fertiliser N applied for expected yield
Delay soil nitrate availability ~ delay N fertiliser application • post-sowing or split (sowing + booting) • N applied up to the 7 leaf stage can benefit yield
Delay soil nitrate availability ~ delay conversion of urea to
nitrate in the soil • DMPP-coated urea (nitrification inhibitor) [EntecTM]
reduces N2O, but also gross margin (no yield benefit) • Polymer coated urea (physical isolation of granule)
may reduce or increase N2O, and also costs more.
Guangdi Li Wagga Wagga Agricultural Institute
Southern NSW ~ Rotation trial conclusions
Treatments 4-year crop sequence Wheat-Canola-Legumes-Wheat Tillage
– Till vs No-till Nitrogen rate
– 0, 25, 50 and 100 kg N/ha Nitrogen type
– Urea, Green Urea, ENTEC
N2O emission and emission factors
Wheat in 2012Treatment N rate Significance
(kg N/ha) No-till Till No-till Till Urea 0 81 130 Tillage, NS
100 179 294 N rate, P< 0.01 0.10 0.16 Entec® 100 105 218 N type, P <0.05 0.02 0.09 Green Urea™ 100 172 343 0.09 0.21Canola in 2013
N rate No-till Till Significance No-till Till Entec® 0 250 332
25 305 354 Tillage, NS 0.05 0.0250 319 305 N rate, NS 0.07 -0.03100 300 306 0.05 -0.03
Canola in 2013N rate No-till Till Significance
Urea 0 154 196 Tillage, NS No-till Till100 186 263 N rate, P =0.058 0.03 0.07
Emission factor (%)
Manual chambers (219 days from 7/8/2012 to 14/3/2013)N2O-N emission (g/ha) Emission factor (%)
Manual chambers (334 days from 23/5/2013 to 22/4/2014)
Auto-chambers (366 days from 23/5/2013 to 22/4/2014)
Emission under legumes
Legumes in 2014 Treatment No-till Till Significance
191 246 Tillage, P =0.058 Pasture (Brown manured) 178 260 Crop type, NS
185 253Legumes in 2014 Crop type No-till Till Significance Emission reduction Lupin (Grain harvested) 255 335 Pea (Grain harvested) 280 353 Tillage, P =0.09 Vetch (Hay cut) 262 334 Crop type, NS Pasture (Hay cut) 321 394 Mean 280 354Pasture in 2013-2015Treatment Lucerne mono-culture (L) Subclover mono-culture (S) -19.3% (L vs S) Phalaris-lucerne mix (PL) Phalaris-subclover mix (PS) -7.6% (PL vs PS) Significance
Pea (Brown manured)
P =0.057
Auto-chambers (386 days from 22/4/14 to 13/5/15)Emission reduction
N2O-N emission (g/ha)Manual chambers 658 days from 14/5/2013 to 3/3/15)
Emission reduction
Manual chambers (279 days from 28/5/14 to 3/3/15)
23.9%20.6%21.5%18.4%21.0%
22.3%31.5%
517417438405
-15.2% (L vs PL)-3.0% (S vs PS)
N2O mitigation strategies ~ southern NSW
No-till practice can potentially reduce N2O emissions
Including perennial grasses in a pasture mix can capture more nitrate, hence reducing the risk of N2O emission during off-season rainfall events
DMPP coated N fertiliser (Entec) can reduce N2O emission, but its high price prevents adoption
Simulations of current and future N2O emissions
and
WNMM Model development
De Li Liu Wagga Wagga Agricultural Institute
MODELLING Model comparison: APSIM, DNDC & WNMM &
Model selection: WNMM & DNDC
Model improvement/development
Simulation of Tamworth previous rotation experimental data
Simulation of Tamworth and Wagga experiments conducted in the project
Simulation N2O under future climate scenarios
Model Improvement
Model comparison: APSIM, DNDC & WNMM Model selection: WNMM & DNDC
Canola+N_wheat+N_barley+N Chickpea -wheat-barley
Model Improvement
Improve WNMM: WNMM NSWDPI version – user friendly interface – graphical user interface (GUI) – Integrating all necessary inputs into
one file, ie. • Site & soil file • management file • model initial file • Model parameters/rates etc
WNMM: – Good performance – Input files ~ 100-200 – Calibration in the model codes by Yong Li
only, no report on actual values used – “Single-user-model”
The first WNMM simulation by a model user - a visiting scientist from Chinese Academy of Science
Anyone (non-modeller) can use this “WNMM NSW DPI version”
Simulation of Wagga experiment (WNMM GUI output)
Simulation of N2O emissions under future climate scenarios
IPCC AR5 CSIRO 3.6 – RCP2.6, RCP4.5, RCP 6.0 & RCP 8.5
Under four rotation system (Tamworth) – CaWB, CpWB, CpWCp & CpS (Ca = canola, W = wheat, B = barley, Cp = chickpea, S = sorghum)
1950–2098 by WNMM & DNDC
Impact of climate change on N2O emission
• RCP2.6 & 4.5 N2O emissions: less than current
• RCP6.0 & 8.5 N2O emissions vary, depending on rotation
• RCP6.0 & 8.5 CaWB, N2O emission will increase by 6–19% • Replace canola with chickpea (CpWB), increases N2O by only 4–15% • Replace barley with chickpea (CpWCp), increase N2O by only 3%
• Rotations including a legume can reduce N2O emissions under
future changing climate.
N2O mitigation strategies ~ modelling Under both current and future climate
• Less fertilizer-dependent cropping
• More legume cropping phase, less N2O emissions
• WNMM model can predict emissions of various scenarios