Biochar Soil Amendment Opportunities

Size: px
Start display at page:

Download "Biochar Soil Amendment Opportunities"

Transcription

1 Biochar Soil Amendment Opportunities Curtis Dell Research 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 1

2 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 Mineralogy Clays 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 (NH 4+ )) 2

3 Organic Matter Benefits 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 Matter Composition 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%) 3

4 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 4

5 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 5

6 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 6

7 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) Tofftrees: Well drained, sandy loam PA study : Sites Duff: Excessively well drained Loam, with high gravel content (30%) Krasinski: Poorly drained, silty clay loam Gibboney: Very poorly drained, silty clay loam with fragipan 7

8 PA study: Findings Biochar stability 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. 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. Graphs from Nguyen et al, SSSAJ 2014 PA study: Findings Soil C concentration Adding biochar in narrow trenches (chisel plowed) lead to the greatest 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 Graphs from Koide et al,

9 PA study: Findings Water retention Biochar addition increased quantity of plant available water 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 g/cm 3 g/cm 3 g/cm Avialable water content Wilting point water content ab a d c d Field capacity water content Biochar alone a a a b b b c d Soil Soil + 1% biochar bc d c f e e Duff bc e e e f Krasinski Gibboney Tofftrees PA study: Findings Switchgrass yield 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. 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 Graphs from Koide et al,

10 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 10

11 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 11