Biochar Application to Subarctic Soils: Effect of biochar on microbial activity after freeze-thaw cycles and plant response at different application rates.

S. Castillo., A. Soria., C. Ping., G. Michaelson., M. Leigh University of Alaska Fairbanks

Google images 2011

High latitude soils are weakly developed and are a challenge to producers (1)

Alaska has some has harsh climatic conditions that affect agriculture (2)

The demand for locally grown produce is gradually increasing .

Abundance of black spruce as feedstock.

What are the differences among black spruce biochar created at different residence times?

What is the influence on microbial activity of soils amended with different biochar types and amounts before and after freeze-thaw?

What is the effect of black spruce biochar on plant yield and nutrient retention at different application rates?

Five different types of biochar were created based on a response surface model conditions.

Black spruce biochar was produced in a pilot scale, fixed bed pyrolysis unit, with a capacity of 1 kg/hr

Temperature was maintained at 550 °C

Chemical analysis of samples

Biochar type(Residence time seconds)

Biochar unit RPM

pH ECmmho/cm

CEC cmol/kg

C/N ratios %

(1) 160.7 8.56 4.73 0.12 12.15 68.59 – 0.26

(2) 134.4 10.8 5.06 0.11 9.77 71.0 – 0.27

(3) 97.3 16.2 4.55 0.15 17.36 67.30 – 0.23

(4) 81.97 21.6 4.29 0.2 16.49 68.90 – 0.24

(5) 73.65 23.8 4.77 0.17 17.07 66.10 - 0.43

Biochar

P (ppm)

K(ppm)

Ca(ppm)

Mg(ppm)

Cu(ppm)

Zn(ppm)

Mn(ppm)

Fe(ppm)

1 <1 44 100 4 198.6 166.6 5.8 214

2 <1 40 62 <1 128.6 113.0 2.6 178

3 <1 38 64 4 168.0 160.8 10.8 1018

4 <1 48 78 6 176.0 161.6 7.0 656

5 130 172 111 13 534.5 558.8 6.1 349

Forest fire charcoal presence on boreal forest has shown greater efficiency of nutrient uptake.( Wardle, 1997)

Freeze and thawing destroys microbial tissue (Haines, 1938)

Burst of CO2 during freeze and thaw (Ross,1972)

Soil goes through physical and chemical changes (DeLuca, 1992)

Treatments based on a response surface model, constructed using Design Expert v7 software

Actively cropped soil and forest soil were collected from the Matanuska Experiment Farm

Microbial activity was measured with 8210-CO2 gas analyzer Columbus instruments 180 C.

Samples underwent 1 cycle of freeze-thaw .

Run Retention time

Biochar amount (g)

1 16.2 6.25

2 16.2 0.95

3 10.8 2.5

4 21.6 2.5

5 16.2 6.25

6 23.84 6.25

7 21.6 10

8 16.2 6.25

9 8.56 6.25

10 10.8 10

11 16.2 6.25

12 16.2 11.25

13 16.2 6.25

Methods:

Design-Expert® Software

Microbial ActivityDesign points above predicted valueDesign points below predicted value673727

64475

X1 = A: RPMX2 = B: Amount of biochar

10.80

13.50

16.20

18.90

21.60

2.50

4.38

6.25

8.13

10.00

60000

217500

375000

532500

690000

M

icro

bia

l A

cti

vit

y

A: RPM B: Amount of biochar

Design-Expert® Software

Microbial ActivityDesign points above predicted valueDesign points below predicted value304356

74443

X1 = A: RPMX2 = B: Amount of biochar

10.80

13.50

16.20

18.90

21.60

2.50

4.38

6.25

8.13

10.00

90000

145000

200000

255000

310000

M

icro

bia

l A

cti

vit

y

A: RPM B: Amount of biochar

Design-Expert® Software

Microbial ActivityDesign points above predicted valueDesign points below predicted value1010.74

319.876

X1 = A: RPMX2 = B: Amount of biochar

10.80

13.50

16.20

18.90

21.60

2.50

4.38

6.25

8.13

10.00

310

487.5

665

842.5

1020

Mic

rob

ial

Ac

tiv

ity

A: RPM B: Amount of biochar

Design-Expert® Software

Microbial ActivityDesign points above predicted valueDesign points below predicted value478.139

218.036

X1 = A: RPMX2 = B: Amount of biochar

10.80

13.50

16.20

18.90

21.60

2.50

4.38

6.25

8.13

10.00

210

277.5

345

412.5

480

M

icro

bia

l A

cti

vit

y

A: RPM B: Amount of biochar

Amend soils with the optimal biochar and evaluate plant response.

Examine the physical change of biochar after freeze – thaw cycles.

Google images

Residence time influenced the chemical characteristics of black spruce biochar specially at the shortest residence time.

Biochar treatments increased microbial activity especially on cultivated soils before and after freeze thaw. It stabilization after few days confirms that biochar can be a long term carbon storage on soils.

The response surface model indicated significance in all models except for forest soils before and after freeze-thaw.

Thanks!

smcastillo@alaska.edu