Applying biochar to soil: Is
it worth the expense?
Jeff Novak, USDA-ARS-CPRC
Northeast Biochar Symposium
November 13, 2009
USDA United States
Department of
Agriculture
USDA-ARS
GRACEnet
program
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. particle
b. pellets
• Conclusions
Pecan biochar enmeshed in the
fabric of a Norfolk soil aggregate
Biochar reactions in soils: C cycle
CO2(g)
Biochar in soil
H2O
leaching
DOC
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).
Leachate DOC
mg L-1
Norfolk soil + %BC
%SOC†
Cumulative CO2 flux
µmol m2 s-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
Drying and
removal from
columns
Soil total N (%TN)
H2O
leaching
NO3-N
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 incubation
Norfolk 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
5.2a
5.4a
5.6a
5.9a
Ex. Acid (cmolc kg-1) 2.4a
2.1a
2.0a
1.5b
CEC (cmolc kg-1)
Improvements in soil physical
properties after adding biochar
Soil water holding capacity (WHC) determined by weight
1.2 PV of di. H20
added to surface
of each soil
Water leachate collected
over 30 hrs (covered to
minimize evaporative losses)
Water leachate weighted
for chemical analyses
and pots weighed daily
Mean (n = 4) % soil water contents (w/w) in a
Norfolk loamy sand treated with biochars
40
Control (0 biochar)
High T switchgrass
CQuest biochar
% H2O in Norfolk (w/w)
35
30
25
20
15
10
5
error bar = 1 SD
0
0
2
4
6
8
days after 1st leaching
10
12
Biochar movement into soils
Biochar added to
Ap horizon
Pecan shell biochar and Norfolk
(before mixing into soil)
Pecan shell biochar and Norfolk
(after mixing into soil)
Biochar also needed
in the E horizon
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 experiment
Column packed
with Norfolk E
Column cut
in 1/2
Norfolk Ap/E
± biochar
leached
with di. H2O
Dark bands are leached biochar
DOC (g) collected from biochar (BC) treatments
(Novak and Busscher, unpublished data)
DOC (g)
N o r f o l k A p / E
Soil + biochar
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
Manure
feedstock
pelletizer
Pyrolyzer
Biochar applied to field
Raw Pellets
(From Dynamotive)
Pelletized biochar
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
Just ask Jeff!
• application;
» Is it worth it?