Biochar Soil Amendment Opportunities.pptx [Read-Only]bioenergy.psu.edu/shortcourses/2018BiocharTorrefied/11...0.6 0.8 Soil Soil + 1% biochar ab a d c bc e bc Wilting point water content
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10/31/2018
1
Biochar Soil Amendment Opportunities
Curtis DellResearch Soil Scientist, USDA‐ARS
and
Adjunct Associate Professor, Ecosystems Science
and Management Department, PSU
Soils 101 Important soil properties for ag and forestry production Soil texture
• % sand, silt, and clay
Mineralogy
• Parent material influences soil properties (especially clay)
• Clay type and amount greatly influences nutrient and water retention
Organic matter
• Amount
• Composition
Mix of materials at various stages of decomposition
Influenced by the type of plants growing at the site
Living and non‐living
Soil structure• 3D arrangement of soil materials
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Soil Texture
% sand, silt, and clay defines soil type
Based only on particle size distribution
Depends on the parent material
Does not vary with management
Loamy soils tend to have best characteristics for plant growth
MineralogyClays have negatively charged surfaces that bond with positively charged molecules Cation Exchange Capacity (CEC)
Different types of clays have different CECs
Important in retention of nutrients (especially ammonium (NH4+))
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Organic MatterBenefits of increasing organic matter Adds cation exchange capacity Can add some anion exchange capacity to retain
negatively charged molecules Adds water holding capacity Improves soil structure, improving water and air
movement Slow release of N, P, K Food/energy source for soil organisms Sequestered form of carbon
Organic MatterComposition of organic matter Complex chemical structure Often characterized by amount of OM in three stages of
decomposition• Labile: living organisms and easily metabolized plant residues
• Slow: Moderately degradable materials
• Stable: Highly resistant to decomposition, contains naturally occurring chars. Very similar to biochar. Main pool of sequestered carbon in soils.
(5‐10%) (40‐50%) (50‐60%)
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Soil structure and aggregation Soil particles have various shapes depending on the type of mineral
Organic matter materials can act as glues to bring mineral particles together
Roots and fungal hype can bring particles together to form aggregates of various size
3D arrangement of aggregates influences amount of pore space
Nitrogen Cycle
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Reported potential benefits of soil amendment with biochar
Sequestration of carbon in soil Increased crop yield Improved soil structure
Improved water holding capacity
Improved nutrient holding capacity
Improved nutrient cycling
Contaminate absorption/retention
Reduced nitrogen leaching Reduced nitrous oxide emissions
Impacts of biochar on soil properties Adding stable soil organic matter well documented
H. Blanco‐Canqui 2016 review of biochar impacts on soil physical properties
• Soil bulk density reduced 3 to 31%• Porosity increased 14 to 64%• Little no effect on penetration resistance (soil compaction) • Wet aggregate stability increased 3 to 226%• Mixed effect of dry aggregate stability• Available water increased 4 to 130%• Saturated hydraulic conductivity decreased in course soil, increased in fine soils
• Change in soil properties usually proportional to biochar application rate• Sandy soils tend to have larger response to biochar than other textures• Long‐term impacts not very clear
Many recent studies on soil biological impacts, but methods vary and comparisons hard to make
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Impacts of biochar on crop yields Large variation in yield impacts
Review by Jeffery et al. in 2011 (20 studies with a range of crops, biochars, and soils)
• 28% decrease to 39% increase reported (20 studies)
• Average across all studies was 5% increase
• Increased yield most frequently associated with liming effect and improved water availability with biochar
• Yield benefit increased with biochar application rate up to about 50 tons/acre
Review by Liu et al. in 2013 (103 studies)• Found average yield increase of 11% with biochar
• Greater response to biochar in acid and sandy soils=
Impact of biochar on N losses (leaching and gas emissions)
Wide range of results reported from increased losses to large reductions, results tend to be site specific
Impacts depend on a range of characteristics such as:• Soil and biochar pH (alkaline biochar in acid soils seems to have most benefit)• Soil texture• Soil moisture (different effects seen with same soil and biochar at different moisture levels) and temperature
• Soil microbial community structure
Multiple mechanisms appear to be involved• Increased absorption of ammonium and nitrate • Changes in abundance and activity (gene expression) of nitrifying and denitrifying bacteria
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Penn State – USDA Biochar Study(Roger Koide, Howard Skinner, Curt Dell, Paul Adler, Bihn Nguyen, and Pat Drohan,
Funded by USDA‐NIFA)
Established switchgrass on four marginally productive sites• Two poorly drained, frequently saturated soils
• Two excessively drained, drought prone
Switchgrass‐derived biochar (~5 tons/acre)• One time application (rototilled 3‐5 in deep), or
• Four annual applications (in narrow trenches between
switchgrass rows)
PA study : SitesDuff: Excessively well drained Loam, with high gravel content (30%)
Tofftrees: Well drained, sandy loam
Gibboney: Very poorly drained, silty clay loam with fragipan
Krasinski: Poorly drained, silty clay loam
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PA study: Findings‐ Biochar stability
Lab studies showed >98% of the biochar C was stable.
Biochar amendment had no measurable impact on the decomposition rate of the native OM.
Electron microscope images showed no noticeable physical change in biochar two years after incorporation into soil.
Switchgrass biochar was stable in all four soils and did not impact the decomposition rate of the native soil organic matter, therefore long‐term C sequestration was increased.
Graphs from Nguyen et al, SSSAJ 2014
PA study: Findings‐ Soil C concentration
With trench (chisel) application of biochar, total C was greater than initial soil C +biochar C
Little loss of native soil C during biochar application
Additional C sequestered by changing to switchgrass
With rotilling, total soil C less than initial soil C +biochar C
Native soil C lost to tillage, partially replaced by biochar and switchgrass C
Adding biochar in narrow trenches (chisel‐plowed) lead to the greatest soil C concentration.
Graphs from Koide et al, 2018
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PA study: Findings – Water retention
Lab studies with thoroughly mixed 1% biochar (by weight) and soil
Available water is difference between soil water content at field capacity and wilting point
Biochar decreased wilting of point of three of the four soils
Biochar increased field capacity of the two well drained soils, but not the poorly drained soils
0.8 to 2.7 additional days of transpiration per season
Biochar addition increased quantity of plant‐available water Avialable water content
g/cm
3
0.0
0.2
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SoilSoil + 1% biochar
ab a
d cd
bc
e
bc
Wilting point water content
g/cm
3
0.00
0.03
0.06
0.09
0.12
0.15
0.18
Field capacity water content
g/cm
3
0.0
0.2
0.4
0.6
0.8
1.0
a a
b bd c
fe
ab
cd
ee
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Biochar alone
Kras-inski
Gib-boney
Duff Toff-trees
PA study: Findings‐ Switchgrass yield
Average annual biomass yield of ~6 ton/acre
Rotill incorporation of biochar increased average yield by 8.3% (across all sites and years)
Even distribution of biochar (rotilling in this case) likely needed to increase plant available water and/or nutrient holding capacity
Biochar addition increased switchgrass biomass yield with full, one‐time application and rotill incorporation, but no impact on yield with incremental chisel‐plow biochar additions.
Graphs from Koide et al, 2018
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PA study: Findings‐ Other measurements
Biochar addition had little impact several other measured properties:
Bacterial and fungal community structure
Several soil enzyme activities
Mycorrhizal colonization
Earthworm numbers
Overall, very low nitrous oxide emissions from switchgrass plots. So, unable to access impact of biochar
PA study: Take home message
Biochar amendment added stable C to the soil
Biochar amendment increased yield if thoroughly mixed with soil
“Best” application method depends on objective
• Decreased soil disturbance lead to greatest C sequestration
• Full incorporation of biochar needed for yield increase
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Recommendations
When the goal is C sequestration, consider loss of native soil C due to tillage to incorporate biochar
• If initial soil C is moderate or high, more C could be lost than is added with biochar
Biochar probably most beneficial for remediating low organic matter and sandy soils such as minelands
Consider the characteristics the biochar, soil, and vegetation grown when selecting best biochar for a specific location/use
• Biochar pH and C:N
• Soil pH, texture, and organic matter
• Range of plant growth requirements
Questions and Discussion
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