This presentation was presented during the 2 Parallel session on Theme 3.2, Managing SOC in: Grasslands and livestock production systems, of the Global Symposium on Soil Organic Carbon that took place in Rome 21-23 March 2017. The presentation was made by Mr. Cornelia Rumpel, from CNRS – INRA – ENS - France, in FAO Hq, Rome

1. Is it possible to mitigate greenhouse gas emissions
from agricultural soil by introduction of temporary
grassland into cropping cycles?
Rumpel, C, Massad, R.S., Crème, A., Carozzi, M., Chabbi, A., Klump, K.,
Leroux, X., Martin, R., Vuichard, N.
Institute for Ecology and Environment, Thiverval-Grignon, France
Laboratory of Functional Ecology and Ecotoxicology, Thiverval-Grignon, France
Laboratory of Microbial Ecology, Lyon France
Laboratory of Climate Sciences and Environment, Gif-sur-Yvette, France

2. GRASSLAND
Forage plants
Permanent plant
cover
high SOM
CROPLAND
Cereal plants
Periods of bare
soil
low SOM
Temporary (ley) grassland
What is the legacy effect of different grassland management practices on GHG
emissions + soil C?
Introduction of temporary (ley) grassland into the cropping cycle could increase
SOM storage, reduce GHG emissions, fertilizer use and leaching (Lemaire et al., 2015)
Agricultural activities lead to reduction of soil organic matter stocks and are also
contributing greatly to greenhouse gas emissions (80% of N2O emissions in France

3.  Lusignan, west of France
 mean annual temperature : 10.5 °C
 mean annual precipitation : 900 mm
 loamy Cambisol
 replicated sampling at 10 cm depth
2005 2006 2007 2008 2009 2010 2011 2012 2013 2014
C Cropland
TG3N+
Temporary grassland :
fertilized, 3 years
Grassland N +
TG6N+
Temporary grassland :
fertilized, 6 years
Grassland N +
TG6N-
Temporary grassland :
unfertilized, 6 years
Grassland N -
G
Permanent grassland :
fertilized
Grassland N +
SAMPLING
Study site
Fertiliser input:
- Grassland: 170-370 kg ha-1a-1
 Cropland: 80-160 kg ha-1a-1

4. (1) to assess the effect of grassland management practices on C storage, SOM,
microbial parameters and N2O emissions of agricultural soils
(2) to determine linkages between microbial characteristics, soil organic matter status
and greenhouse gas fluxes and
.
Objectives and Experimental approach
Grassland
management Soil variables
MOS quality and quantity
Activities of key
microorganisms
Functional
groups of
microorganisms
N2O emission
In the lab
N2O emissions

5. 0
50
100
150
200
250
C 3yr G 6yr G 6yr Guf 9 yr G
gm-2
a b
ab
c
d
C TG3N+ TG6N+ TG6N- G
Carbon storage (2014) in 0-10 cm
In productive grasslands, fertilisation is necessary to store C
 GRASSLAND ↗  FERTILIZATION ↗ DURATION ≈

6. Variation of C
stocks during 9
years
t/ha
C sequestration
‰ par an
Cr
-1,9 b ± 1,4 -4,6 b ± 3,0
TG3N+
-0,6 b ± 0,8 -1,4 b ± 2,0
TG6N+
0,5 ab ± 1,2 1,3 ab ± 3,2
TG6N-
0,0 ab ± 0,7 0,1 ab ± 1,6
G
2,8 a ± 2,0 7,1 a ± 5,3
Development of C storage in the treatments of
the longterm experimental site
0-30 cm
y = 1.2x - 5.0
R² = 0.96
-6
-4
-2
0
2
4
6
8
0 2 4 6 8 10
Carbonsequestration
‰peryear
Years of grassland

7. 0
1
2
3
4
C TG3N+TG6N+ TG6N- G
C6/C5
a b b a c
0
1
2
3
4
5
6
7
C TG3N+ TG6N+ TG6N- G
soilsugarcontent
(mgg-1)
 GRASSLAND
Content ↗
Plant origin ↗
c b b d a
Sugars content Sugar origin
Effects of grassland duration and N fertilisation on
content and forms of hemicellulosic sugars
Microbial sugars
Plant sugars
FERTILIZATION
Content ↗
Plant origin ↗
DURATION
Content ≈
Plant origin ≈

8. 0
2
4
6
8
10
12
14
C TG3N+ TG6N+ TG6N- G
(µgg-1)
Nmin NO3-
 GRASSLAND ↗
b ab a ab a
b b b b
Effects of grassland duration and N fertilisation on
mineral N forms
 FERTILIZATION ≈
a
 DURATION ↗

9. Legacy effect on GHG emissions measured during 42
days extrapolated to 1 yr
0
5
10
15
20
25
30
35
C TG3N+ TG6N+ TG6N- G G-R
AnnualGHGemissions
gCm2
 GRASSLAND ↗  DURATION ≈  FERTILIZATION ↗
-2.1 -0.6 0,5 0 3.1 C storage per yr
(2005-2014)

10. Legacy effect on microbial activity related to GHG
emissions
-0.1
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
DépendancerelativedelapoductionbrutedeN2O
àl'apportdeCorg
Dépendance au N
Dépendance au C
Dépendance au N+C
C TG3N+ TG6N+ GTG6N-
DependanceofN2Oemissionson
labileCinput
In soils with grassland history, N2O emissions are less dependant on labile C
input as compared to cropland
Legacy effect of temporary grassland on microbial activity related to N2O
emissions

11. 0
2
4
6
8
10
Cr TG3N+ TG6N+ TG6N-
Maizeyields2011
tha-1
c b a d
Maize yields in the first year after grassland
conversion into cropland
Legacy effect of grassland management on yield in first year after conversion

12. More soil C
More available
N
Legacy effects of temporary mowed grassland on soil C
and GHG emission as compared to permanent crop
Aggregation
Labile plant-
derived C
Permanent soil cover
Denitrification activity
GHG emissionsBiomass production
Higher yields
As SOM-microbial activity and GHG emissions are intemately linked, a compromise
between different ecosystem services has to be found.
Innovative N fertilisation stategies have to be developped, e.g. legume
use during grassland phase, low emission organic fertilisers during
cropland phase
+ N fertilisation

13. Acknowledgements
Funding
Thank you for your attention !
Excellent work of technical staff of SOERE ACBB

14. Variables
Elemental composition
 Lignin signature
 Sugar signature
 Microbial biomass
 Biolog
 Potential C, N mineralisation
 Physical fractions
Legacy effect on soil parametersDim2(12.84%)
Dim 1 (32.9%)
G: more C, higher labile C, higher biological activity, more available nutrients
TG: legacy effect on SOM parameters only achieved after several years of fertilised TG
In TG more fresh plant-derived C