Engil Pereira, Emma Suddick , Johan Six University of California, Davis

On-farm field experiment to investigate biochar effects on soil structure and N2O emissions

Engil Pereira, Emma Suddick, Johan SixUniversity of California, Davis

2012 US Biochar Conference – Sonoma State University, Rohnert Park, CA. July 29 – August 1, 2012

Outline

• Biochar production and study site: Dixon Ridge Farm

• Soil structure – Potential for additional C sequestration

• N2O emissions - Link with N2O consumers

• Concluding remarks

Dixon Ridge Farm

• Winters, CA• Organic walnut farm and

processing facility• BioMax 50: Waste management

and energy production• Savings: $45,000 / year• Closing the loop: Biochar!

Russ Lester, co-owner of Dixon Ridge Farms

Walnut biocharCharacteristics

Temperature 900 - 950°C

pH 9.7

Ash (%) 46.4

C (%) 55.3

N (%) 0.47

Olsen P (mg kg-1) 902

BET Surface area (m2 g-1) 227.1

CEC (meq 100 g-1) 33.4

Study site• Established in June 2010 at Dixon Ridge Farm• Area: 12 acres• 4 treatments with 3 replicates each• Compost and cover crop

Treatment Amount (ton ha-1)

Control n/a

Biochar 5

Compost 5

Biochar + Compost 2.5 each

Tree Row

Tractor Row

Sampling Locations:

Experimental Approach

Biochar+

Soil

GHG emissions(CO2 and N2O)

Soil mineral N

Soil pHSoil microorganisms

Soil structure(aggregation)

Soil moisture content

Soil structure: Aggregation

Key properties

- Aggregates -> Protected fractions: C sequestration

- Maintenance of soil moisture and aeration

- Soil microorganismsLarge Macroaggregates

(> 2000 μm)

Small Macroaggregates (250 - 2000 μm)

Microaggregates (53 - 250 μm)

Silt and Clay (< 53 μm)

Biochar and soil aggregates

• Due to surface charge, biochar may promote soil aggregation

• This mechanism may increase C sequestration

Sampling June 2011 June 2012

Depth 15 cm

Location Tree and tractor road

Fractions - Large Macroaggregates- Small Macroaggregates- Microaggregates- Silt and clay

Large Macroaggregates (> 2000 μm)

Control Biochar Compost Biochar + Compost

0%

5%

10%

15%

20%

25%

30%

35%

40%

Tree Row

20112012

Prop

ortio

n of

soil

(%)


0%5%

10%15%20%25%30%35%40%45%50%

Tractor Row

20112012

Prop

ortio

n of

soil

(%)

Small Macroaggregates (250 - 2000 μm)


0%

5%

10%

15%

20%

25%

30%

35%

Tree Row

20112012

Prop

ortio

n of

soil

(%)


0%

5%

10%

15%

20%

25%

30%

35%

Tractor Row

20112012

Prop

ortio

n of

soil

(%)

Microaggregates (53 - 250 μm)

Silt and Clay (< 53 μm) - UnaggregatedControl Biochar Compost Biochar +

Compost

0%5%

10%15%20%25%30%35%40%45%

Tree Row

20112012

Prop

ortio

n of

soil

(%)


0%

5%

10%

15%

20%

25%

30%

35%

40%

Tractor Row

20112012

Prop

ortio

n of

soil

(%)


0%2%4%6%8%

10%12%14%16%18%20%

Tree Row

20112012

Prop

ortio

n of

soil

(%)


0%2%4%6%8%

10%12%14%16%18%

Tractor Row

20112012

Prop

ortio

n of

soil

(%)

Biochar and soil aggregates

• Biochar did increase soil aggregation when combined to compost during the first year of study;

• During the second year of observations, macroaggregates were disrupted, freeing microaggregates and silt and clay particles.

• In conclusion, in this study biochar did not sustain an increase in soil aggregation and therefore additional C sequestration.

Potential to reduce N2O emissions

Biochar NO3-

Leaching

Denitrification

N2ONH4

+

N2O

NitrificationN2

By increasing soil CEC, biochar will lead to NH4

+ adsorption and prevention of nitrification.

No Amendment Walnut Biochar0

10

20

30

40

50

60

Soil CEC

Na

(meq

100

g-1)

60%

N2O sampling

• Samplings happen once a week• Or, for 7 days after an event (Irrigation, fertilization,

precipitation).

Tree Row

Tractor Row

N2O emissions – 1st year

7.13.10 Irriga

tion

7.20.10

7.28.10

7.30.10

8.12.10 Irriga

tion

8.14.10

8.16.10

8.27.10

8.31.10

9.13.10

9.17.10

10.4.10

10.25.10 Precipita

tion

10.27.10

10.29.10

11.2.10

11.8.10 Precipita

tion

11.10.11

11.28.10 Precipita

tion

11.30.10

12.2.10

2.21.11 Precipita

tion

2.24.11

3.28.114.8.11

4.13.11

4.19.11

5.10.11 Irriga

tion

5.12.11

6.15.110

2

4

6

8

10

12

14

16

18

g N

2O-N

ha-

1 da

y-1

7.13.10 Irriga

tion

7.20.10

7.28.10

7.30.10

8.12.10 Irriga

tion

8.14.10

8.16.10

8.27.10

8.31.10

9.13.10

9.17.10

10.4.10

10.25.10 Precipita

tion

10.27.10

10.29.10

11.2.10

11.8.10 Precipita

tion

11.10.11

11.28.10 Precipita

tion

11.30.10

12.2.10

2.21.11 Precipita

tion

2.24.11

3.28.114.8.11

4.13.11

4.19.11

5.10.11 Irriga

tion

5.12.11

6.15.1102468

101214161820

g N

2O-N

ha-

1 da

y-1

Tree Row

Tractor RowControl

Biochar

Tree Tractor02468

1012141618

Cumulative - Irrigation 08.11.11

g N

2O-N

ha-

1 ev

ent-

1

Tree Tractor02468

10121416

Cumulative 05.27.12 Irrigation

ControlBiocharCompostB+C

g N

2O-N

ha-

1 ev

ent-

1

Tree Tractor0

50100150200250300350400

Irrigation + Fertilization - Sept 2011

g N

2O-N

ha-

1 ev

ent-

1

N2O emissions – 2nd year

Link with N2O consumers

Control Walnut Biochar0E+001E+062E+063E+064E+065E+066E+067E+068E+069E+06 Nitrous oxide reductase (nosZ)

copi

es o

f nos

Z g-

1 so

il

NH4+ NO3

- NO2- NO N2O N2

amoA nirS nosZ

nirK

N2O producers

N2O consumers

- Pot trial study using walnut shell biochar

- Extraction of microbial DNA- qPCR: Quantification of

functional genes- N2O reduction to N2

Concluding Remarks

• Decreases in N2O emissions, when observed, happen after wet events (irrigation or precipitation) and in the tree row

• Such decreases may be associated to an increase in the bacterial abundance that performs the reduction of N2O to N2

• Biochar closes the loop at Dixon Ridge Farm with economic and environmental benefits.

Acknowledgements

• California Energy Commission• CNPq - Brazil• Six lab members, in special to Rafaela Conz,

Garret Heinz and Neele Holzenkaempfer

Documents

Engil Pereira, Emma Suddick , Johan Six University of California, Davis