Applying biochar to soil: Is it worth the expense?

Jeff Novak, USDA-ARS-CPRC

Northeast Biochar Symposium

November 13, 2009

USDAUnited StatesDepartment ofAgriculture

USDA-ARSGRACEnetprogram

Outline:

• Biochar reactions in soil (C and N cycles)• Nutrients released from biochars• Soil physical improvements after biochar

addition• Biochar movement into soil• Biochar applications to soil

a. particleb. pellets

• Conclusions

Pecan biochar enmeshed in thefabric of a Norfolk soil aggregate

Biochar reactions in soils: C cycle

CO2(g)

DOCH2O leaching

Biochar in soil

Table 1. Mean %soil organic carbon (SOC) content, cumulative CO2 fluxes and dissolved organic carbon concentration (DOC 0.45µm) in water leachate from a Norfolk soil after 67 days of incubation with high temp pecan shell biochar (BC).

Norfolk soil + %BC %SOC†

Cumulative CO2 flux

µmol m2 s-1

Leachate DOC

mg L-1

0 1.75a 22.8a 28.3a

0.5 1.83b 20.8a 30.1a

1.0 2.20c 20.9a 33.0a

2.0 2.92d 14.5a 43.9a†Values are means from n = 3 and tested for significances using an ANOVA (Novak et al. accepted for publication in Geoderma).

Biochar reactions in soils: N cycle

H2O leaching

Drying and removal from columns

NO3-N

Soil total N (%TN)

Table 2. Mean %soil total nitrogen (TN) content dissolved nitrate –N (NO3-N) concentration (0.45µm) in water leachate from a Norfolk soil after 67 days of incubation with high temp pecan shell biochar (BC).

Norfolk soil + %BC %TN† Leachate NO3-N (mg L-1)

0 0.123a 28.3a

0.5 0.130a 30.1a

1.0 0.107a 33.0a

2.0 0.120a 43.9a

†Values are means from n = 3 and tested for significances using an ANOVA (Novak et al. accepted for publication in Geoderma).

Nutrients released from soil + pecan biochar:

After 67 d incubationNorfolk soil + % biochar

Soil property 0 0.5 1.0 2.0

pH 5.2a 5.6b 5.9c 6.4d

K (mg kg-1) 26a 47b 49c 69d

Ca (mg kg-1) 392a 462b 537c 692d

CEC (cmolc kg-1) 5.2a 5.4a 5.6a 5.9a

Ex. Acid (cmolc kg-1) 2.4a 2.1a 2.0a 1.5b

Improvements in soil physical properties after adding biochar

1.2 PV of di. H20 added to surface of each soil

Water leachate collectedover 30 hrs (covered tominimize evaporative losses)

Water leachate weighted for chemical analyses and pots weighed daily

Soil water holding capacity (WHC) determined by weight

Mean (n = 4) % soil water contents (w/w) in a Norfolk loamy sand treated with biochars

days after 1st leaching

0 2 4 6 8 10 12

% H

2O i

n N

orf

olk

(w

/w)

0

5

10

15

20

25

30

35

40

Control (0 biochar)High T switchgrassCQuest biochar

error bar = 1 SD

Biochar movement into soils

Biochar added toAp horizon

Biochar also neededin the E horizon

Pecan shell biochar and Norfolk(before mixing into soil)

Pecan shell biochar and Norfolk(after mixing into soil)

What we need to achieve is biochar in Ap and E horizons:

• Biochar that can be surface applied, disked in, and then migrates through soil into subsurface hard layers.

• We believe that biochar may assist in aggregate formation.

Norfolk Ap

Norfolk E (hard layer)

Biochar leaching experimentColumn packed with Norfolk E

Norfolk Ap/E± biochar leached with di. H2O

Column cut in 1/2

Dark bands are leached biochar

DOC (g) collected from biochar (BC) treatments (Novak and Busscher, unpublished data)

Norfolk Ap/E

Soil + biochar

DOC (g)

Mean* SD

Control (no BC) 4.67a 1.71

BC 1 2.24a 0.83

BC 2 1.53a 1.63

BC 3 29.82b 10.51

LSD (0.05) 11.51

Biochar applications to soil

Biochar applied to field

Manure feedstock

pelletizer

Raw Pellets

Pyrolyzer

Pelletized biochar(From Dynamotive)

Conclusions

• Biochar adds C and nutrients to soils, influences the soil N cycle (+/-);

• Some biochars can act like a liming agent and increase a soils WHC;

• Biochars can move into soils;• Biochar processing for field• application;

» Is it worth it?

Just ask Jeff!