ICOS Science Conference 2022: Day 2, Session 15

1. TO PLOUGH OR NOT TO PLOUGH:
CO2 & N2O EC MEASUREMENTS ON WAGENINGEN GRASSLAND
A.HENSEN, I. VELZEBOER, P. WINTJEN, W.C.M. VAN DEN BULK, J.P. LOLLINGA, M.M.
MOERMAN, K.F.A. FRUMAU, D. VAN DINTHER, J. ZHANG, G.VELTHOF, J.VAN T HULL, M.ROS

2. CO2 & N2O EXCHANGE
• Try to establish emission factors
• EF’f mainly chamber study based
N2O
Slootdorp
Cabauw
Ludjewad
Zegveld
(Veenw.)
CH4
CO2
Loobos
(bos)
Horstermeer
(Natuur.)
Reeuwijk (Veenweide)
Oukoop (Intensief)
Stein (extensief)
Zevenbergen
(aardappel/ui)
Snelle kamer Oukoop (TDL)
Aardappels (TDL)
Respiratie Loobos (NDIR)
Autobox Cabauw (GC)
Sloot meting Oukoop
Sloot meting Stein
(Opt-Ac)
Kamer cop sloot (Opt-Ac)
2m2 Kamer (GC)
Zegveld(intensief)
(Opt-Ac)

3. TEMPORAL VARIATION
N2O
-100
100
300
500
700
900
14-08-02 19-08-02 24-08-02 29-08-02
Emission
(g/day/ha)
mobile
Box A
Box B
Fertilizer
Rain
N2O
-100
100
300
500
700
900
14-08-02 19-08-02 24-08-02 29-08-02
Emission
(g/day/ha)
mobile
Box A
Box B
Fertilizer
Rain

4. EDDY COVARIANCE TRIED BEFORE
QCL at Reeuwijk
Eddy correlatie fluxen Reeuwijk
Februari 2006
-50
50
150
8-2-06
12
9-2-06
00
9-2-06
12
10-2-06
00
10-2-06
12
11-2-06
00
11-2-06
12
12-2-06
00
12-2-06
12
13-2-06
00
13-2-06
12
Datum
N
2
O
[ng
N/m
2
s]
-500
500
1500
CH
4
[ng
C/m
2
s]
EC N2O Box N2O
EC CH4 Box CH4
How to compare
multiple fields ???
Same meteo same soil

5. EDDY COVARIANCE TRIED BEFORE
QCL at Reeuwijk
Eddy correlatie fluxen Reeuwijk
Februari 2006
-50
50
150
8-2-06
12
9-2-06
00
9-2-06
12
10-2-06
00
10-2-06
12
11-2-06
00
11-2-06
12
12-2-06
00
12-2-06
12
13-2-06
00
13-2-06
12
Datum
N
2
O
[ng
N/m
2
s]
-500
500
1500
CH
4
[ng
C/m
2
s]
EC N2O Box N2O
EC CH4 Box CH4
How to compare
multiple fields ???
Same meteo same soil
IN A “CHEAP” WAY

6. 3 FIELDS 1 SYSTEM
H
L
220v

7. NOT TO FAR NOT TO HIGH
high
low
big
small
Large eddies important tube length les important footprint bigger
H
L

8. NOT TO FAR NOT TO HIGH
Large eddies important tube length les important footprint bigger
Small eddies important tube length critical footprint smaller
high
low
big
small
H
L

9. NOT TO FAR NOT TO HIGH
Large eddies important tube length les important footprint bigger
Small eddies important tube length critical footprint smaller
Danger: flux outside footpint short inlet short power line
high
low
big
small
H
L

10. NOT TO FAR NOT TO HIGH
Nice for footprint long inlet long power line
high
low
big
small
H
L
Large eddies important tube length les important footprint bigger
Small eddies important tube length critical footprint smaller
Danger: flux outside footpint short inlet short power line

11. 3 FIELDS
SET-UP
180m
200m
L =80 m L south = 40m

12. 3 FIELDS
SET-UP

13. 3 FIELDS
SET-UP CHAMBER MEASUREMENTS
Fchamber = slconc ⋅Mgas / Vm ⋅ h
With same Aerodyne analyser !

14. MAIN EVENTS DURING MEASUREMENTS
Event data Field 3 summer wheat Field 4 new seeding grass Field 5 - reference
20 April Grass Grass Grass
28 April Start measurements Start measurements Start measurements
3 May Mow/manure/till Mow/till Mow/manure
6 May Plough/seed Plough/seed
4 June Till
14 June Till Mow
17 June Remove grass and manure
9 August Harvest Mow
12 August Reseed Manure Manure

15. HALF-HOURLY CONCENTRATIONS VISUALIZED AS BOX-WHISKER-PLOTS BI-WEEKLY
RESULTS

16. AVERAGED DIURNAL CYCLES
RESULTS

17. COSPECTRUM OF THE VERTICAL GAS FLUX - FROM MEASURED RAW TIME SERIES OF CONCENTRATIONS AND VERTICAL WIND
VISUALISE ABILITY OF EC SETUP TO CAPTURE THE EDDIES CONTRIBUTING TO THE FLUX
0.2 sec
15 min 100s 10s

18. CORRECTING HIGH-FREQUENCY FLUX LOSSES
IN-SITU COSPECTRAL METHOD (ICO)
0.2 sec
15 min 100s 10s

19. DAMPING FACTORS – SUMMER WHEAT – FIELD 3
RESULTS
THEORETICAL
EMPIRIC

20. DAMPING FACTORS – GRASS – FIELD 4
RESULTS

21. DAMPING FACTORS –REFERENCE – FIELD 5
RESULTS

22. AVERAGED DIURNAL CYCLES
RESULTS

23. AVERAGED DIURNAL CYCLES
RESULTS
plough

24. AVERAGED DIURNAL CYCLES
RESULTS
Harvest
Manure
reseed

25. MEAN (AVG) AND STANDARD DEVIATION (STD) OF CONCENTRATIONS (CONC) AND FLUXES FOR CO2 AND N2O
RESULTS
CO2 [flux unit: µg C m-2 s-1; conc.
unit: ppm]
N2O [flux unit: ng N m-2 s-1;
conc. unit: ppb]
Field 3
Wheat
Field 4
Grass
Field 5
Ref
Field 3
Wheat
Field 4
Grass
Field 5
Ref
Emission
[%]
56.0 51.0 44.0 73.0 75.0 67.0
Deposition
[%]
44.0 49.0 56.0 27.0 25.0 33.0
Avg. flux -4.0 -18.6 -27.6 11.2 10.9 5.8
Std. flux 87.6 97.0 89.9 27.7 24.5 19.8
Avg. conc. 431 429 431 320 322 320
Std. conc. 36.7 37.6 36.2 6.1 7.4 6.0
Plausible
data [%]
14.0 15.0 12.0 14.0 15.0 12.0

26. FLUX CONTRIBUTION : HISTOGRAM OF HALF-HOURLY FLUXES DURING ENTIRE CAMPAIGN
RESULTS

27. BIWEEKLY TIME SERIES OF HALF-HOURLY CO2 AND N2O FLUXES
RESULTS

28. THE FLUX DOES NOT ONLY COME FROM “YOUR OWN FIELD”
FOOTPRINT
𝑓3 = 𝐹3G − 𝐹out ⋅ 𝑎3_out 𝑎3_3
𝑓
4 = 𝐹4G − 𝑓3 ⋅ 𝑎4_3 − 𝐹out ⋅ 𝑎4_out 𝑎4_4
𝑓5 = 𝐹5G − 𝑓3 ⋅ 𝑎5_3 − 𝑓
4 ⋅ 𝑎5_4 𝑎5_5

29. CUMULATIVE CO2 EXCHANGE OF ALL FIELDS (F3=WHEAT, F4=GRASS, F5=REFERENCE)
RESULTS

30. CUMULATIVE CO2 EXCHANGE OF ALL FIELDS (F3=WHEAT, F4=GRASS, F5=REFERENCE)
RESULTS
REF
Grass
Wheat

31. CUMULATIVE N2O EXCHANGE OF ALL FIELDS (F3=WHEAT, F4=GRASS, F5=REFERENCE)
RESULTS
Grass
Wheat
REF

32. CUMULATIVE CO2 AND N2O EXCHANGE ESTIMATED FROM FLUX CHAMBER MEASUREMENTS
RESULTS

33. CUMULATIVE CO2 AND N2O EXCHANGE ESTIMATED FROM FLUX CHAMBER MEASUREMENTS
RESULTS
Eddy Covariance Chamber
measurements
CO2 [g C m-2] N2O [g N ha-1] N2O [g N ha-1]
Org Aw Org Aw
Wheat 53.4 223.9 1658.9 1322.6 596.7
New grass -34.5 39.5 1798.8 1842.5 639.8
Reference -223.7 -249.2 894.5 463.8 39.2
Cumulative CO2 and N2O flux estimated from eddy covariance – original (org) and area
weighted (aw) - and flux chamber measurements for all fields in their respective units
54 224
-35 40
-224 -250
1.6 1.3
1.7 1.8
-0.9 0.4
[ Kg N ha-1 ] [ Kg N ha-1 ]
0.60
0.64
0.04

34. CUMULATIVE CO2 AND N2O EXCHANGE ESTIMATED FROM FLUX CHAMBER MEASUREMENTS
RESULTS
Eddy Covariance Chamber
measurements
CO2 [g C m-2] N2O [g N ha-1] N2O [g N ha-1]
Org Aw Org Aw
Wheat 53.4 223.9 1658.9 1322.6 596.7
New grass -34.5 39.5 1798.8 1842.5 639.8
Reference -223.7 -249.2 894.5 463.8 39.2
Cumulative CO2 and N2O flux estimated from eddy covariance – original (org) and area
weighted (aw) - and flux chamber measurements for all fields in their respective units
54 224
-35 40
-224 -250
1.6 1.3
1.7 1.8
-0.9 0.4
[ Kg N ha-1 ] [ Kg N ha-1 ]
0.60
0.64
0.04
!!!

35. CUMULATIVE CO2 AND N2O EXCHANGE
RESULTS
Area Weighted net CO2 eq
fluxes
CO2 to atmosphere compared
to REF
g CO2 m-2 eq
Field CO2 N2O Sum CO2 role N2O role Total
Wheat 821 57 877 -90% -8% -98%
Grass 145 79 224 -16% -8% -25%
Ref
grass
-914 20 -894 101% -1% 100%
Net area flux data
CO2 equivalent
emission to the
atmosphere and
comparison with the
reference net
exchange.

36. CUMULATIVE CO2 AND N2O EXCHANGE
RESULTS
Area Weighted net CO2 eq
fluxes
CO2 to atmosphere compared
to REF
g CO2 m-2 eq
Field CO2 N2O Sum CO2 role N2O role Total
Wheat 821 57 877 -90% -8% -98%
Grass 145 79 224 -16% -8% -25%
Ref
grass
-914 20 -894 101% -1% 100%
Net area flux data
CO2 equivalent
emission to the
atmosphere and
comparison with the
reference net
exchange.
Three fields: together on the way to carbon neutrallity * *non agronomer’s joke do not quote

37. CONCLUSION TO PLOUGH OR NOT TO PLOUGH
• The eddy covariance measurements worked well even with the inletlines up to 90m
• Flux damping seemed to be around 20% where we expected 40% based on theory
• Ploughing lead to the expected significant CO2 emission on top of which there is
extra N2O
• The role of CO2 in this story is one order of magnitude more than the role of N2O
• Three field EC can be done but we ended up with only 15% true data coverage per
field
• This is however 24/7 distributed
• So probably still an improvement from weekly chamber measurements
• From a 9 month net CO2 emission point of view: do not plough.

38. CONCLUSION TO PLOUGH OR NOT TO PLOUGH
• The eddy covariance measurements worked well even with the inletlines up to 90m
• Flux damping seemed to be around 20% where we expected 40% based on theory
• Ploughing lead to the expected significant CO2 emission on top of which there is
extra N2O
• The role of CO2 in this story is one order of magnitude more than the role of N2O
• Three field EC can be done but we ended up with only 15% true data coverage per
field
• This is however 24/7 distributed
• So probably still an improvement from weekly chamber measurements
• From a (non agronomer’s) 9 month net CO2 emission point of view: do not plough.

39. YOUR TIME
THANK YOU FOR