Applying biochar to soil: Is it worth the expense?
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Transcript of Applying biochar to soil: Is it worth the expense?
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!