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THE EFFECTS OF BIOCHAR ON FOREST SOIL CHEMICAL PROPERTIES AND TREE GROWTH

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(1)

Kristin McElligott, Mark Coleman, and Debbie Page-Dumroese

THE EFFECTS OF BIOCHAR ON FOREST SOIL CHEMICAL

PROPERTIES AND TREE GROWTH

(2)

Biochar Application in Forestry

Presentation Overview

---

• Context and Research Justification

• Positive & Negative Aspects of Biochar

• Research Results

Biochar/soil incubation study

Greenhouse Bioassay: Poplar growth response to biochar additions

• Application and Feasibility

• Potential Implications for Land Managers

(3)

Context

---

• Remove forest biomass/residues

Forest health improvement, fuels reduction

Bioenergy production: portable fast pyrolysis units

• Concerns associated with removals

Alter nutrient cycling, reduce SOC, site degradation over time?

Economics

• Mollify concerns with biochar application?

Return/retain site nutrients

Improve soil properties

Long-term C sequestration

(4)

Forestry, Bioenergy, & Carbon ---

• Forestry: Source of biomass, need for fuels reduction

• Bioenergy: Co-production of biofuels and biochar via pyrolysis

Energy extraction without nutrient removals

• Carbon: Biochar is 70-80% C, creates long- term soil carbon sinks

(5)

Biochar Pros and Cons ---

Carbon sequestration potential

Soil nutrient & water retention

Bioavailabilityplant productivity

Soil fertility, microbial activity

Inhibit nutrient leaching

Reduce N2O and CH4 emissions

Polycyclic aromatic hydrocarbons (PAH)

Heavy metals

Priming

Raise pH?

Reduce plant growth?

+ _

(6)

Research Justification ---

Environmental Implications: Demonstrate effects of biochar on forest soil properties and woody biomass growth

1. Biochar as a forest soil amendment:

Compare effects of biochar and application method on forest and agricultural soil chemical properties

2. Greenhouse bioassay:

Investigate if plant growth/biomass can be enhanced with biochar

Uncertainties associated with regions/soils

Unique INW soils, volcanic ash inputs

Positive and negative results associated with biochar research

(7)

Biochar Incubation Study ---

• Laboratory incubation study (Jan-Aug 2010)

• Demonstrate biochar effects among various soils

Spodosol, Andisol, Mollisol

• Demonstrate application methods

Top-dressing, Incorporation

• One rate: 25 Mg ha-1

• 3 treatments x 3 soils x 6 replicates = 54 soil columns

(8)

Soil Types

---

Soil Classification Horizon Location

Forest Andisol medial over loamy, mixed, frigid Alfic

Udivitrand Bw Clearwater County,

ID

Forest Spodosol sandy, mixed, frigid Aquic Haplorthod E Priest Lake, ID

Agricultural Mollisol

fine-silty, mixed, superactive, mesic

Pachic Ultic Haploxeroll Ap Moscow, Idaho

(9)

Biochar Incubation Study ---

pH

OM (%)

Total C (%)

Total N (%)

NH4-N (µg g-1)

NO3-N (µg g-1)

Available K (µg g-1)

Available P (µg g-1)

Hypothesis: Biochar additions will enhance standard soil chemical properties of all soils

CEC (cmol kg-1)

K (cmol kg-1)

Ca (cmol kg-1)

Mg (cmol kg-1)

Na (cmol kg-1)

Microbial Biomass

Leachate N analysis Properties of interest:

(10)

Measurements and data analysis ---

• Cores destructively sampled at 30 weeks

Soil chemical properties, leachate N, and microbial biomass

• General linear model used to test for significant effects (α=0.05)

Treatment type

Soil type

Interactions

• LS Means & Tukey’s post hoc procedure (SAS)

(11)

Main Effects on Soil Properties ---

OM increased by 7%

Mixed treatment increased CEC by 5% relative to the control

Available K increased in surface (13%) and mixed (27%) treatments

Control Surface Mixed 0

1 2 3 4 5

a b b

Organic Matter (%)

Control Surface Mixed 0

5 10 15 20 25

ab b a

CEC (cmol kg-1 )

Control Surface Mixed 0

50 100 150 200 250

a

b c

Available K (µg g-1 )

Biochar effects for all soil types combined. significant differences at P < 0.05.

(12)

Interactions

---

C increased for all soils - magnitude varies by soil

Surface and mixed treatment decreased NH4 (63%, 42%) in the Andisol only

pH increased by 8% in the Spodosol

K increased in the Andisol (16%, 21%) and Mollisol (19% mixed trt)

Andisol Spodosol Mollisol 0.0

0.5 1.0 1.5

b

a

b a

a a a

a

ab

K (cmol/kg)

Andisol Spodosol Mollisol 0

20 40 60 a

a

a b

a b a

a

N-Ammonia (ug/g) a

Andisol Spodosol Mollisol 3

4 5 6

a a

b

a ab

a

a a

a

pH

Andisol Spodosol Mollisol 0

2 4 6 8

10 Control

Top Mix b

a a

bc cd

ef f

ed ed

Carbon %

treatment*soil interactions

(13)

Leachate

---

• Biochar reduces NH4 (38%, 99%) and NO3 (56%, 94%) in the Mollisol

Andisol Spodosol Mollisol 0

20 40 60

80 a

b

c

a a a

a a a

Control Surface Mixed

Leachate NH4mg L-1

Andisol Spodosol Mollisol 0

200 400 600 800 1000

a

b

a c

a a

a a

-1 Leachate NOmg L3 a

Leachate N response to biochar treatments

(14)

Test Val ue

pH 6.8

CEC (cmol kg-1) 30

OM (%) 9

Total C (%) 62

Total N (%) 0.18

K (cmol kg-1) 1.6

Ca (cmol kg-1) 2.2

Mg (cmol kg-1) 0.35

Na (cmol kg-1) 0.17

NH4+(µg/g) 3.3

NO3+NO2(µg/g) < 1.6 Available K (µg/g) 710 Available P (µg/g) 17

Nutrient Value: direct or indirect effects of biochar?

Indirect = nutrient retention, change in physical properties, soil interactions

Dynamotive CQuest Biochar

---

(15)

Results Summary ---

• Mixed biochar treatments alter exchange sites and increases CEC of all three soils

• Both biochar treatments resulted in significant increases in C and OM among all soil types

• K significantly increased in both the Andisol and Mollisol with biochar additions, but was unchanged in the Spodosol

• NH4-N significantly decreased with biochar treatments in the Andisol only

(16)

Discussion Points ---

Application method matters: pH, CEC, and available K

Incorporation may accelerate organo-mineral relationships

Increases in C, OM and available K  direct input from biochar

Magnitude of difference varies - Differences in starting colloid properties (OM, C, Clay)

Short lived benefits?

Decreases in NH4

Losses due to leaching, nitrification, volatilization, or immobilization ?

Dilution effect, N-depleted amendment

pH increase in Spodosol only

Result of starting pH of soil (3.8) and biochar (6.8)

Improved nutrient retention

Relevant in fertilized systems

(17)

Biochar is effective at significantly enhancing soil C, OM, K, CEC, and pH on a short timescale

Improved soil quality and site productivity over time, maybe

Concerns with NH4reductions in INW soils

Can we expect these results in the field?

Depends on rate, biochar, application method, and plant & microbial interactions, time

Soil amelioration tool and can

increase the recalcitrant soil carbon pool, long-term carbon sequestration

Repeatable?

Likely, using same char source

Different char, different results?

Application

---

(18)

Tree Growth Response ---

Investigate effects of biochar on woody biomass

Greenhouse bioassay:

Investigate if soil nutrient supply, uptake, and plant growth can be increased with biochar additions

(19)

Research Justification ---

• Current Biochar Research

Agricultural Soil

Crop-growth response

Highly degraded soils

Tropical and Arid Regions

• Research Gaps

Forest Soils

Tree growth response

Temperate regions

(20)

Greenhouse Bioassay ---

Biochar and Sand Rates

0%, 25%, 50%

Sand = inert amendment and control

With/without fertilizer

8 weeks, 2 harvests, 10 reps

100 total cuttings

Effects on different soil types?

Coarse- and fine-textured Andisol

Expected an increase Poplar growth with biochar additions

Ashy-pumiceous, glassy Xeric Vitricryands medial over loamy, mixed, frigid Alfic Udivitrand

(21)

Measurement and Analysis ---

Harvest = separating the plant into leaves, stems, cutting and roots

Drying, weighing, grinding

Leaf C & N

General linear model used to test for significant effects (α=0.05)

treatment type (control, biochar, sand)

rate (0, 25, 50%)

fertilizer (yes, no)

biomass, and leaf N properties

LS Means, Tukey’s post hoc (SAS)

(22)

Results Overview ---

Soil type is significant

Best growth in FA

No Biochar effect

Total, above- and below-ground biomass (p>0.05)

both soils

Fertilizer effect

Total Biomass FA & CA

Above-ground biomass FA

Negative sand response in CA only

Total and above-ground biomass

No fertilizer effect

Biochar Sand

(23)

Biochar has no significant effect on Total Biomass

Sand amendments significantly reduce Total Biomass Coarse Andisol

0 2 4 6 8 10

a a

a

Control 25% Char 50% Char

Total Biomass (g)

0 2 4 6 8 10

b a

b

Control 25% Sand 50% Sand

Total Biomass (g)

Results

---

(24)

0 2 4 6

a b

ab ab ab

ab

Control 25% Char 50% Char

Above-ground Biomass (g)

0 2 4 6

ab a ab

b

ab ab

No Fert Fert

Control 25% Sand 50% Sand

Above-ground Biomass (g)

Results

---

No response with biochar or sand

Biochar + Fert has greatest positive response

Physical properties of char

Potential negative growth response at high rates

Fertilizer additions could avoid negative effects Fine Andisol

(25)

Results

---

• Biochar: no significant differences among rates

Follows trend of sand amendment

• Sand: decreased growth for CA and not FA

Harv e st 2 char*soiltype

0 1 2 3 4

5 a

ab

c bc

abc ab

Control 25%Char 50%Char

Above-ground Biomass (g)

Harv e st 2 sand*soiltype

0 1 2 3 4 5

a ab

c a

bc ab

Coarse Andisol Fine Andisol

Control 25%Sand 50%Sand

Above-ground Biomass (g)

Soil Comparison

(26)

Biochar significantly reduces leaf N

Control 25% Char 50% Char 0.0

0.5 1.0 1.5 2.0 2.5

a

b b

Leaf % N

Control 25% Sand 50% Sand 0.0

0.5 1.0 1.5 2.0 2.5

a

ab b

Leaf % N

Results

---

Leaf N

(27)

• Application in forestry  Why not?

• No biochar effect, but potential for negative consequences

Decreased leaf N

Short- or long-term effects on productivity?

• Soil texture effects response

Biochar application rate is important

Bioassay Summary

---

(28)

Predicted: Slight effect of biochar on forest soil properties

Mostly positive enhancements in nutrient status

Direct and indirect

Application method

Do these soil alterations effect forest productivity

Probably not - depends on biochar rate

Alterations over time

Short vs. Long-term Effects

Implications

---

(29)

• Reduce reliance on fossil fuels

• Promote rural development

• Improve economics & finance forest management activities?

• Reduce wildfire risk

• Eliminate in-woods burning of biomass

• Sequester C

• Conserve or improve site nutrients

• Enhance forest productivity

Bioenergy & Biochar Co-production Potential

---

(30)

University of Idaho Sustainability Center

Acknowledgements ---

We thank the Moscow Forestry Sciences Lab and the UI Center for Forest Nursery and Seedling Research for work space, the IFTNC for assistance, Dynamotive Energy Systems for biochar donations, USDA

FS and UI Sustainability Center for funding.

References

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