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

Contents Research context Experimental field lay out Objectives Results Conclusions

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

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)

Field layout Transplant spring 2006

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)

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

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

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

Analysis Root systems Soil Organic Carbon

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

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)

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

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 10 - 30 30 - 45 45 - 60 60 - 75 75 - 90 90 - 100 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 10 - 30 30 - 45 45 - 60 60 - 75 75 - 90 90 - 100 d B bc B ab B bc c bc b ab ab

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 10 - 30 30 - 45 45 - 60 60 - 75 75 - 90 90 - 100 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 10 - 30 30 - 45 45 - 60 60 - 75 75 - 90 90 - 100 d B bc B ab B bc c bc b ab ab

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

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

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

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

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)

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)

Results – SOC SOC fractions for 0 to 10 cm depth a a a a a a ab ab ab bc b c

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

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

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.

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