1. Application of DNDC and DayCent models to
estimate present and future nitrous oxide
emissions and biomass production from
Irish agriculture
Mohamed Abdalla; Mike Jones and
Mike Williams
TCD, Botany department

2. Introduction
DNDC DayCent
Started as N model Started as C model
requiring quick dynamics requiring slow dynamics
Added crop and soil C Added daily water and N
pool model
Legacy: Legacy:
Only one year rotation More flexibility in crop
possible systems
Less legitimate for slow Less legitimate for fast N
C dynamics dynamics

3. General objectives
• To test DNDC and DayCent models for
simulation of N2O emissions and biomass
production from Irish agriculture
• To simulate the effectiveness of different
management systems to mitigate GHG
emissions
• To assess the impacts of future climate change
on gas fluxes and biomass production

4. Arable Agriculture:
1. Application of the DNDC model to predict emissions of
N2O from arable soils.
i- Effectiveness of Reduced N
ii- Effectiveness of Reduced tillage
iii- Effectiveness of Reduced tillage-Cover crop

5. N1 = 140-160 kg N
N2 = 70-80 kg N
Materials & Methods N3 = 0 kg N
Conventional-Till Reduced-Till

6. Materials & Methods
Measurements carried for two seasons (2004-2005)

7. Materials & Methods
• Soil nitrate, moisture, temperature were measured
simultaneously with the N2O fluxes.
•Three climate scenarios were investigated: a
baseline from Carlow historical climate data (1961-
1990) and two future scenarios (high and low
temperature sensitivity; (2061-2090) from the C4I
(2008) based on the (HadCM3) and the A1B
emission scenario (IPCC, 2001).
•The DeComposition-DeNitrification model (DNDC)
version 8.9 was applied.

8. Results Abdalla et al. (2009
Fig.: Comparison of model-simulated (●) and field measured (○) N2O flux from the high (upper)
medium (bottom) and low (lower) fertilized conventional tillage in 2004 (A, C, E) and 2005 (B, D, F).

9. Results Abdalla et al. (2009)
Fig.: Comparison of model-simulated (●) and field measured (○) N2O flux from the high (upper),
medium (bottom) and low (lower) fertilized reduced tillage in 2004 (A, C, E) and 2005 (B, D, F).

10. Results
Table 1: Observed and modelled seasonal N2O emissions from the arable
conventional and reduced tillage plots.
Seasonal emissions ( kg N2O-N ha-1) Rd (%)
2004 season Treatment Observation Model
Conventional tillage 140 kg N ha-1 0.788 a 0.780 -1
70 kg N ha-1 0.269 b 0.350 +30
0 kg N ha-1 0.002 c 0.110 + >100
Reduced tillage 140 kg N ha-1 0.978 a 0.590 -40
70 kg N ha-1 0.494 b 0.220 -55
0 kg N ha-1 0.087 c 0.030 -66
2005 season
Conventional tillage 160 kg N ha-1 1.053 a 0.993 -6
80 kg N ha-1 0.563 b 0.450 -20
0 kg N ha-1 0.170 c 0.110 -35
Reduced tillage 160 kg N ha-1 1.058 a 0.793 -25
80 kg N ha-1 0.567 b 0.320 -44
0 kg N ha-1 0.135 c 0.010 -93
•Measured EFs: 0.4 to 0.7%, whilst modeled EFs: 0.3 to 0.6% Abdalla et al. (2009)

11. N1 = 140kg N
N2 = 70 kg N
Materials & Methods N3 = 0 kg N
Conventional-Till Reduced Till-Cover crop
N2O measurements took place for 18 months 2008-2009

12. 40 a)
Results 30
(g N2O-N ha-1d-1)
20
N2O flux
10
Fig.: Comparison of model-
0
simulated (solid lines) and
-10
field measured (○) N2O flux
from the high (a), medium -20
Mar-08 Jun-08 Sep-08 Dec-08 Mar-09 Jun-09 Sep-09
(b) and low (c) fertilized
conventional tillage in 2008- 40
b)
2009 30
(g N2O-N ha-1d-1)
20
N2O flux
10
0
-10
-20
Mar-08 Jun-08 Sep-08 Dec-08 Mar-09 Jun-09 Sep-09
40 c)
30
(g N2O-N ha-1d-1)
20
N2O flux
10
0
-10
-20
Mar-08 Jun-08 Sep-08 Dec-08 Mar-09 Jun-09 Sep-09
Rueangritsarakul et al., Submitted

13. 140
a)
120
Results 100
(g N2O-N ha-1d-1)
80
N2O flux
60
Fig.: Comparison of model- 40
simulated (solid lines) and 20
0
field measured (○) N2O flux
-20
from the high (a), medium Mar-08 Jun-08 Sep-08 Dec-08 Mar-09 Jun-09 Sep-09
(b) and low (c) fertilized 140
b)
reduced tillage-cover crop 120
in 2008-2009 100
(g N2O-N ha-1d-1)
80
N2O flux
60
40
20
0
-20
Mar-08 Jun-08 Sep-08 Dec-08 Mar-09 Jun-09 Sep-09
Peak represent > 30% 140
c)
of annual flux 120
100
(g N2O-N ha-1d-1)
80
N2O flux
60
40
20
0
-20
Mar-08 Jun-08 Sep-08 Dec-08 Mar-09 Jun-09 Sep-09
Rueangritsarakul et al., Submitted

14. Results
Table: Observed and modeled cumulative N2O emissions from the conventional
and reduced tillage-cover crop management.
Treatment Cumulative N2O
emission (kg N ha-1)
2004 season Observation Model Relative deviation (%)
Conventional tillage
140 kg N ha-1 1.74 1.71 -1.8
70 kg N ha-1 1.37 1.16 -15
0 kg N ha-1 0.86 1.13 +31
Reduced tillage-cover
crop
140 kg N ha-1 2.42 3.24 +33.6
70 kg N ha-1 2.17 2.36 +8.7
0 kg N ha-1 0.87 1.46 +67.8
Rueangritsarakul et al., Submitted

15. Results
Fig.: Correlation between measured and modelled N2O from arable field
Simulated N 2O-N flux (kg ha-1y-1)
3.5
3
2.5
2
1.5
1
0.5
0
0 0.5 1 1.5 2 2.5 3
-1 -1
Observed N 2O-N flux (kg ha y )
y = 1.12x + 0.07, r2 = 0.92 Rueangritsarakul et al., Submitted

16. 120 a)
Results 100
Nitrate concentration
80
(kg N ha-1)
Fig.: Comparison of model- 60
simulated (solid line) and 40
field measured (closed 20
circle) soil nitrate from 140 0
kg N ha-1 (a), 70 kg N ha-1 Mar-08 Jun-08 Sep-08 Dec-08 Mar-09 Jun-09 Sep-09
(b) and no fertilizer applied 60 b)
treatments (c) for the
Nitrate concentration
50
conventional tillage. Arrows
(kg N ha-1)
40
show time of fertilizer 30
application. 20
10
0
Mar-08 Jun-08 Sep-08 Dec-08 Mar-09 Jun-09 Sep-09
10 c)
Nitrate concentration
8
(kg N ha-1)
6
4
2
0
Mar-08 Jun-08 Sep-08 Dec-08 Mar-09 Jun-09 Sep-09
Rueangritsarakul et al., Submitted

17. 140 a)
Results 120
Nitrate concentration
100
(kg N ha-1)
Fig.: Comparison of model- 80
simulated (solid line) and 60
field measured (closed 40
circle) soil nitrate from 140 20
kg N ha-1 (a), 70 kg N ha-1 0
(b) and no fertilizer applied Mar-08 Jun-08 Sep-08 Dec-08 Mar-09 Jun-09 Sep-09
treatments (c) for the 70 b)
reduced-cover crop tillage. 60
Nitrate concentration
50
Arrows show time of fertilizer
(kg N ha-1)
40
application.
30
20
10
0
Mar-08 Jun-08 Sep-08 Dec-08 Mar-09 Jun-09 Sep-09
20 c)
Nitrate concentration
15
(kg N ha-1)
10
5
0
Mar-08 Jun-08 Sep-08 Dec-08 Mar-09 Jun-09 Sep-09
Rueangritsarakul et al.,Submitted

18. Results
Fig.: Correlation between measured and modelled soil temperature from
the arable field
Y = 0.77x +1.96, r2 = 0.9
Rueangritsarakul et al., Submitted

19. Results
Fig: N2O fluxes
under climate
change
Conventional
tillage 2004
High (о)
Low (▲)
Base (●)
Abdalla et al. (2010a)

20. Results
Fig: N2O fluxes
under climate
change
Reduced
tillage 2004
High (о)
Low (▲)
Base (●)
Abdalla et al. (2010a)

21. Table: Simulated cumulative N2O emissions (kg N2O-N ha-1) under different N
fertilizer levels, tillage systems and climate scenarios: baseline, high
temperature sensitive and low temperature sensitive. Values with different
letters, are significantly different from each other (P<0.05).
Treatment Conventional tillage
baseline High temp sen. Low temp sen.
140 kg N ha-1 9.8 ab 5.7 a
5.5 a
70 kg N ha-1 8.6 ac 4.5 b
4.9 b
0 kg N ha-1 6.9 bc 3.1 c
4.0 c
Reduced tillage
140 kg N ha-1 6.5 a
5.9 a 11 ab
70 kg N ha-1 5.5 b 9.9 ac 5.3 b
0 kg N ha-1 4.4 c
5.0 c 9.0 abc
Abdalla et al. (2010a)

22. Results
Figure 6: Effects of climate
change on simulated N2O
emissions for reduced tillage
spring barley incorporating a
mustard cover crop (a) and
conventional tillage spring
barley (b) at 140 kg N ha-1
under baseline (thin line),
high (thick line) and low
(dash line) temperature
sensitive climate scenarios.
Rueangritsarakul et al., Submitted

23. Table: Simulated cumulative N2O fluxes at high N rate (kg N2O-N ha-1) under
different management and climate scenarios: baseline, high temperature-sensitive
and low temperature-sensitive. Different letters in are significantly different from
each other (p<0.05).
Treatment Conventional tillage
baseline High temp sen. Low temp sen.
140 kg N ha-1
2.3 a 9.8 b 3.7 a
Reduced tillage-Cover crop
140 kg N ha-1
9.4 c 21.5 d 9.6 c
Reduced Tillage 6.5
5.9 11
Rueangritsarakul et al., Submitted

24. Conclusions
1. DNDC is suitable for predicting N2O fluxes under
high N fertilizer (140-160 kg N ha-1) rather than under
low N fertilizer (0-80 kg N ha-1) and describes best
CT rather than RT or RT-CC management.
2. By reducing the applied nitrogen fertilizer by 50 %
compared to the normal field rate, N2O emissions
could be reduced by >50%.
3. Application of RT or RT-CC to mitigate present or
future N2O may be not successful.

25. Grasslands:
2. Application of the DNDC and Daycent models to predict
emissions of N2O and biomass production from grasslands.

26. 172 kg N/ha
Materials & Methods 28 kg N/ha
Silage cut in May
Measurements carried from 2003 to 2004

27. Results a
Fig.: Comparisons
of DNDC model-
simulated (●) and
field measured (о)
N2O fluxes from the
fertilized (a) and
control (b) pasture
treatments in 2003/
2004. Arrow show
time of fertilizer
application.
b
DNDC overestimated:
Fertilized: 132%
Control: 258%
Abdalla et al. (2010b)

28. Results
WFPS (%) at 0-20 cm depth 60
50
40
30
20
10
0
Oct-03 Jan-04 Mar-04 Jun-04 Aug-04 Nov-04 Jan-05
Fig.: Comparisons between the simulated (●) and field measured (о)
WFPS from the cut and grazed pasture for DNDC model in 2003/04.
(Error bars for measured values are ± standard error).
Abdalla et al. (2010b)

29. Results
Nitrous oxide emissions (g NO-N ha d )
110
-1
-1
Fig.: Comparisons of 90
DayCent model-
2
70
simulated (●) and field
measured (о) N2O fluxes 50
from the fertilized (a)
30
and control (b) pasture
treatments in 2003/ 10
2004. Arrow show time
-10
of fertilizer application. Nitrous oxide emissions (g NO-N ha-1 d-1 ) 26-Oct-03 09-Jan-04 24-Mar-04 07-Jun-04 21-Aug-04 04-Nov-04 18-Jan-05
20
15
2
10
5
0
-5
-10
26-Oct-03 09-Jan-04 24-Mar-04 07-Jun-04 21-Aug-04 04-Nov-04 18-Jan-05
Abdalla et al. (2010b)

30. Results
Table: Annual measured flux, DayCent predicted flux, DNDC predicted flux and
differences between predicted and measured fluxes of N2O (kg N2O-N ha-1).
Treatment Measured DayCent DNDC Flux difference Flux difference
flux (DayCent- (DNDC-measured)
measured)
Control 1.0 a 0.5 3.58 -0.5 +2.58
fertilized 2.6 b 3.6 4.06 +1.0 +3.44
DayCent:
Fertilized: +32%
Control: -57% (poor)
Abdalla et al. (2010b)

31. Results 4
a
Above ground dry biomass (t ha )
-1
Fig.: Weekly DayCent 3
(a) and DNDC (b)
simulated (●) and field 2
measured (о) grass
biomass in 2004. 1
0
0 10 20 30 40 50
Weeks of the year
DayCent: -23%
DNDC: -75%
4
b
Above ground dry biomass (t ha )
-1
3
2
1
0
0 10 20 30 40 50
Weeks of the year
Abdalla et al. (2010b)

32. Results
Fig.: Effects of climate change on N2O emissions from the grass field for the
high (▲) and low (о) temperature sensitivity climate data compared with
measured baseline climate (●). Arrow show time of fertilizer application.
Nitrous oxide emissions (g N2 O-N ha-1 d-1 )
60
50
40
30
20
10
0
0 50 100 150 200 250 300 350 400
Days of the year
Abdalla et al. (2010b)

33. Results
Fig.: Effects of climate change on above ground grass biomass
production for the high (о) and low (▲) temperature sensitivity climate
scenarios compared with measured baseline climate (●).
4
Above ground biomass (t ha -1 )
3
2
1
0
-3 2 7 12 17 22 27 32 37 42 47 52
Weeks of the year
Abdalla et al. (2010b)

34. Conclusions
1. Although, further improvement is possible
DayCent model effectively estimates N2O fluxes
and biomass production from the grassland.
2. Prediction of DayCent under control plots was
poor with a relative deviation of (-57%)
3. Climate change will favour the Irish low N input
grasslands with more biomass production and no
significant change in N2O flux.

35. Conclusions
4. Future higher above ground biomass production
would encourage farmers to increase grazing
intensity. This would increase emissions of
methane (CH4) and excretal N deposition from
grazing animals.
5. Alternatively, farmers could apply less N fertilizer
to the pasture to achieve the current amount of
above ground biomass production without
making significant change on N2O or CH4 fluxes.

36. Acknowledgements
Komsan Rueangritsarakul; Suresh Kumar; Bruce Osborne, Gary lanigan, Pete
Smith; Martin Wattenbach; Jagadeesh Yeluripati; Per Ambus; James Burke;
Brendan Roth;
EPA
GreengrassEurope
Met Éireann
Teagasc, Carlow
Thanks for yours attention