1. Carlo Chimento, Stefano Amaducci
Assessment of carbon sequestration potential in soil and in belowground biomass of six perennial bioenergy crops
Carlo Chimento, Stefano Amaducci
Department of Sustainable Vegetable Productions
Università Cattolica del Sacro Cuore di Piacenza
18 December 2014 – Wageningen

2. Contents Research context Experimental field lay out Objectives
Results
Conclusions

3. Research context Agronomical aspect: Biomass production
Environmental aspect:
C sequestration ….

4. Field layout Rhizomatous grasses Arundo donax L. (Giant reed)
Miscanthus x giganteus (Miscanthus)
Panicum virgatum (Switchgrass)
Trees SRF
Populus spp (Poplar)
Robinia pseudoacacia (Black locust)
Salix (Willow)

5. Field layout
Transplant spring 2006

6. Field layout Rhizomatous grasses Arundo donax L. (Giant reed)
Miscanthus x giganteus (Miscanthus)
Panicum virgatum (Switchgrass)
Trees SRF
Populus spp (Poplar)
Robinia pseudoacacia (Black locust)
Salix (Willow)

7. Field layout Rhizomatous grasses Arundo donax L. (Giant reed)
Miscanthus x giganteus (Miscanthus)
Panicum virgatum (Switchgrass)
Trees SRF
Populus spp (Poplar)
Robinia pseudoacacia (Black locust)
Salix (Willow)
Surface area: 8100 m-2

8. Objectives
Main objective: identify which crop has the highest soil C sequestration potential
Root biomass production and distribution along the soil profile
Assessment of SOC stock variation and its degree of stabilization

9. Sampling Two sampling were performed Root systems Soil Organic Carbon
0 – 10
0 – 10
10 – 30
10 – 30
30 – 45
30 – 60
45 – 60
60 – 75
60 – 100
75 – 90
90 – 100
Root systems
Soil Organic Carbon

10. Analysis
Root systems
Soil Organic Carbon

11. Analysis Root systems Soil Organic Carbon
Root Biomass Weight RBW (t ha-1)

12. Analysis Root systems Soil Organic Carbon
Total Soil Organic Carbon (g Kg-1)
Soil Organic Carbon stock (g m-2)
Root Biomass Weight RBW (t ha-1)

13. SOC fractions and stabilization mechanisms
Wet sieving, density and ……
cPOM (2000 – 250 µm) and fPOM (250 – 53 m), unprotected SOC fractions
iPOM (250 – 53 µm), physically protected SOC fraction
……… chemical fractionation
HC ds+c chemically protected SOC fraction
HC µs+c chemically protected SOC fraction
NHC ds+c biochemically protected SOC fraction
NHC µs+c biochemically protected SOC fraction

14. Results – Root systems Root Biomass Weigth (t ha-1) Soil depth (cm)
Giant reed 2 4 6 8
Miscanthus
Switchgrass
Black locust
Poplar
Willow
0 - 10
6.4 t ha-1
7.8 t ha-1
12 t ha-1
5.7 t ha-1
4.2 t ha-1
3.6 t ha-1 cd B ab AB a A bc b a
43 %
26 % ab ab a
Soil depth (cm)
0 - 10 d B bc B ab B bc c bc b ab ab

15. Results – Root systems Root Biomass Weigth (t ha-1) Soil depth (cm)
Giant reed 2 4 6 8
Miscanthus
Switchgrass
Black locust
Poplar
Willow
0 - 10
6.4 t ha-1
7.8 t ha-1
12 t ha-1
5.7 t ha-1
4.2 t ha-1
3.6 t ha-1 cd B ab AB a A bc b a
57 %
74 % ab ab a
Soil depth (cm)
0 - 10 d B bc B ab B bc c bc b ab ab

16. Results – Root systems Root Biomass Wheigth (t ha-1)2 4 6 8 10
Switchgrass
Giant reed
Miscanthus
Willow
Black locust
Poplar a b
abc ab bc c
Root biomass weight (t ha-1)
0 to 30 cm soil depth
30 to 100 cm soil depth

17. Results – Root systems Root Biomass Wheigth (t ha-1)2 4 6 8 10
Switchgrass
Giant reed
Miscanthus
Willow
Black locust
Poplar a b
abc ab bc c
Root biomass weight (t ha-1)
0 to 30 cm soil depth
30 to 100 cm soil depth
1.2 t ha-1
3.7 t ha-1

18. Results – Root systems Root Biomass Wheigth (t ha-1)2 4 6 8 10
Switchgrass
Giant reed
Miscanthus
Willow
Black locust
Poplar a b
abc ab bc c
Root biomass weight (t ha-1)
0 to 30 cm soil depth
30 to 100 cm soil depth
1.2 t ha-1
3.7 t ha-1

19. Results – SOC Total Soil Organic Carbon Content Depth (cm) Pr (>F)2 4 6 8 10 12 14
Willow
Miscanthus
Switchgrass
Giant reed
Poplar
Black locust
Arable field
Total Soil Organic Carbon (g kg-1) a ab
abc
bcd
cde de e
0 – 10 cm soil depth
Depth (cm)
Pr (>F)
0 – 10
< 0.001
10 – 30
0.53
30 – 60
0.41
60 – 100
0.84

20. Results – SOC Soil Organic Carbon stock Depth (cm) Pr (>F) 0 – 10
0 – 10 cm soil depth
Arable field a
500
1000
1500
2000
750
1250
1750
Willow
Miscanthus
Switchgrass
Giant reed
Poplar
Black locust ab bc c
Depth (cm)
Pr (>F)
0 – 10
< 0.001
10 – 30
0.099
30 – 60
0.656
60 – 100
0.835
0 – 100
0.854
Soil Organic Carbon stock (g m-2)

21. Results – SOC Soil Organic Carbon stock Depth (cm) Pr (>F) 0 – 10
0 – 10 cm soil depth
120 99 95 80
g m-2 yr -1
Arable field a
500
1000
1500
2000
750
1250
1750
Willow
Miscanthus
Switchgrass
Giant reed
Poplar
Black locust ab bc c
Depth (cm)
Pr (>F)
0 – 10
< 0.001
10 – 30
0.099
30 – 60
0.656
60 – 100
0.835
0 – 100
0.854
Soil Organic Carbon stock (g m-2)

22. Results – SOC SOC fractions for 0 to 10 cm depth a a a a a a ab ab abbc b c

23. Results – SOC SOC fractions for 0 to 10 cm depth
400
1000
iPOM
cPOM
fPOM
Sum of POM-C a a
800
300 b a a
Pariculate organic matter C (g of C m-2)
600 b a
200
Woody crops a
Pariculate organic matter C (g of C m-2)
400 b
100
200
Arable field
Herbaceous crops
Woody crops
Herbaceous crops
Woody crops
Herbaceous crops
Woody crops
Herbaceous crops

24. Results - summarizing After six years ……
SOC stock increased only in the first soil layer, and the increase of the SOC stock has been faster in woody than herbaceous species
Leaf litter seems to play a major role in SOC accumulation and stabilization
Root biomass could play an important role in the long term especially if the bioenergy crop will be reconverted in arable land

25. Conclusions After six years ……
woody species showed the greatest SOC sequestration potential in the first soil layer, but their ability to allocate root biomass in the deeper soil layers was limited.
herbaceous species allocated a high amount of root biomass in the deeper soil layers, but only switchgrass and miscanthus sequester C in the first soil layer.

26. Thank you for your attention . . . . .