Biochar: Impacts on Soil Microbes and the Nitrogen Cycle Kurt Spokas USDA-ARS, Soil and Water Management Unit, St. Paul, MN Adjunct Professor University of Minnesota Department of Soil, Water and Climate Presented at the 21 ACEEE Forum on Energy Efficiency in Agriculture Madison, WI. February 7-9, 21
Biochar Properties of Biochar Stable (resident times 1 to 1, yrs) High carbon content Mechanism to lock atmospheric carbon in soil Gaining significant attention >Carbon Storage (Climate Change) Biochar can store atmospheric carbon, potentially providing a mechanism for reduction in atmospheric CO 2 levels >Soil Improvements Improves water quality, plant growth, water infiltration Improves soil fertility/nutrient cycling Reduces GHG emissions (N 2 O, CH 4 ) >Bio-energy Source (Renewable energy source)
ARS Biochar Research Part of new ARS multi-location: Biochar and Pyrolysis Initiative 6 ARS locations: Ames, IA; Kimberly, ID; St. Paul, MN; Big Spring, TX; Florence, SC; Prosser, WA. +additional sites in the near future Biochar used in replicated field plots Continuous corn (same crop for comparison) In addition to following crop yield and soil carbon: Soil gas concentrations and trace gas fluxes Seedling Emergence/Initial seedling growth rates
Biochar Impacts on Soil Microbes & N Cycling 26 different biochars evaluated 11 different biomass parent materials Hardwood, softwood, corn stover, corn cob, macadamia nut, peanut shell, sawdust, algae, coconut shell, turkey manure, distillers grain Represents a cross-sectional sampling of available biochars C content 1 to 84 % N content.1 to 2.7 % Production Temperatures 35 to 85 o C Variety of pyrolysis processes Fast, slow, hydrothermal, gasification
25 2 2 15 1 5 CO2 Production (ug CO2.5g char-1 day -1 ) BC-1 BC-2 BC-3 BC-4 BC-5 BC-6 BC-7 BC-8 BC-9 BC-1 BC-11 BC-12 BC-13 BC-14 BC-15 BC-16 BC-17 BC-18 BC-19 BC-2 BC-21 BC-22 BC-23 BC-24 BC-25 BC-26-5 4 2-2 5 25 1 5-5 CH4 Production (pg CH4.5g char-1 d -1 ) N2 O Production (pg N2 O.5g char-1 d -1 ) Corn (Stover,Cob,DG) Pine Shells (peanut/mac) Pine + Compost Turkey manure Wood Algae -4 Biochar Alone 511 337 2237 Soil = 22 ng N 2 O g soil -1 day -1 Soil = -5 ng CH 4 g soil -1 day -1
Correction for Biochar production CO 2 Production Rate Corrrected = biochar + soil biochar ( CO2 CO2 ), 5g soil (t d ) biochar + soil CO2 is the total CO 2 production from the soil + biochar + water incubation (µg CO 2 ) at time t d biochar CO 2 is the total CO 2 production (µg) at time t d for the biochar + water incubation t d is the time of sampling (days)
CO 2 Production (ug CO 2 g soil -1 d -1 ) Soil Control BC-1 BC-2 BC-3 BC-4 BC-5 BC-6 BC-7 BC-8 BC-9 Soil Control BC-1 BC-2 BC-3 BC-4 BC-5 BC-6 BC-7 BC-8 BC-9 BC-1 BC-11 BC-1 BC-11 BC-12 BC-13 BC-12 BC-13 BC-14 BC-14 BC-15 BC-15 BC-16 BC-16 BC-17 BC-18 BC-19 BC-2 BC-21 BC-22 BC-23 BC-24 BC-25 BC-17 BC-18 BC-19 BC-2 BC-21 BC-22 BC-23 BC-24 BC-25 BC-26 BC-26 1 8 6 5 4 3 2 1 4 3 2 1-1 -2-3 CH4 Production/Oxidation (ng CH4 g soil-1 d -1 ) Soil Control BC-1 BC-2 BC-3 BC-4 BC-5 BC-6 BC-7 BC-8 BC-9 BC-1 BC-11 BC-12 BC-13 BC-14 BC-15 BC-16 BC-17 BC-18 BC-19 BC-2 BC-21 BC-22 BC-23 BC-24 BC-25 BC-26 5 4 3 2 1 3 2 1-4 Soil + Biochar N2 O Production (ng N2 O g soil-1 d -1 ) Corn (Stover,Cob,DG) Pine Shells (peanut/mac) Pine+Compost Turkey manure Wood Algae
Influence of biochar additions on GHG Production.2 CO 2 Production (mg CO 2 /g soil /day). -.2 -.4 -.6 N 2 O Production (ng N 2 O/g soil /day) -.8 1.8 1.6 1.4 1.2 1..8.6.4.2...5 1. 1.5 2. 2.5 3. 3.5..5 1. 1.5 2. 2.5 3. 3.5 CH 4 Production (ng CH 4 /g soil /day) -1-2 -3-4 -5-6 -7..5 1. 1.5 2. 2.5 3. 3.5 Biochar Amount (g)
Brief Overview of N-cycle Organic N Nitrogen Uptake (plants/microbes) Mineralization Ammonium (NH 4+ ) Nitrification Nitrate (NO 3- ) Emitted to atmosphere Nitrogen fixation N 2 Nitrite (NO 2- ) Nitric Oxide (NO) Nitrous Oxide (N 2 O) Nitrogen Gas (N 2 ) Denitrification
Closer Look at N-cycling Nitrite (ppm) Nitrate (ppm) NH4 (ppm) 1 8 6 4 2.5.4.3.2.1. 5 4 3 Ammonium 2 1 1 2 3..5 1. 1.5 2. 2.5 3. 3.5 1. Biochar Alone.5. 1 2 3 1. Biochar Alone.5. 1 2 3 Nitrate Nitrite..5 1. 1.5 2. 2.5 3. 3.5 Biochar Amount (g)
N-cycling: Sterilized soil + biochar 14 12 1 8 6 4 2 18 16 14 12 1 8 6 4 2 Nitrate (ppm) BC Alone Non Sterile Soil Non sterile Soil+BC Sterile Soil Sterile Soil+BC BC Alone Non Sterile Soil Non sterile Soil+BC Sterile Soil Sterile Soil+BC ND Ammonium (ppm) Pine (softwood) char (55 o C) Slow pyrolysis Pine (softwood) char (55 o C) Slow pyrolysis
Putting the pieces together: Not quite a full picture yet Organic N Nitrogen Uptake (plants/microbes) Mineralization Ammonium (NH 4+ ) Nitrification Decreased amount Nitrogen fixation Increased amounts (occasionally) Nitrate (NO 3- ) Nitrite (NO 2- ) N 2 Decreased amount Nitric Oxide (NO) Nitrous Oxide (N 2 O) Nitrogen Gas (N 2 ) Denitrification
Conclusions Positive effect observed so far in laboratory Reduction in N 2 O production potential Appears to be a consequence of biochar impacting the nitrification process Accumulation of NH + 4 and decreased NO- 3 Inhibiting nitrification and denitrification? No absolute biochar trends However, a majority of biochars Reduced soil CO 2 respiration or no significant increase Reduced CH 4 oxidation activity Reduced N 2 O production activity Reduced NO 3 availability
Acknowledgements We would like to acknowledge the cooperation: Dynamotive Energy Systems Fast pyrloysis char (CQuest ) through non-funded CRADA agreement Best Energies Slow pyrolysis char through a non-funded CRADA agreement Northern Tilth NC Farm Center for Innovation and Sustainability National Council for Air and Stream Improvement (NCASI) Illinois Sustainable Technology Center (ISTC) [Univ. of Illinois] Biochar Brokers Chip Energy USDA-ARS Biochar and Pyrolysis Initiative Technical Support : Martin dusaire, Tia Phan, Lindsey Watson, and Lianne Endo
Rosemount, MN Biochar Field Trials Small scale triplicate plots (16 x 16 ) >Largely due to the limited availability of biochar. (Application rate : 2, lbs/acre) Fast pyrolysis biochar (sawdust, CQuest TM Dynamotive 1 ) With and without manure addition (5, lb/acre) Slow pyrolysis biochar (woodchip, Best Energies 1 ) Slow pyrolysis biochar (macadamia nut, Biochar Brokers 1 ) Slow pyrolysis updraft gasifier (wood pellets, Chip Energy 1 ) [Fall 29] Larger strip plots (16 x 93 ) Hardwood charcoal (ground lump charcoal, Kingsford 1 ) Slow pyrolysis biochar (macadamia nut, Biochar Brokers 1 ) 3 rates: 5,, 1, and 2, lb/acre 1-Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by USDA implies no approval of the product to the exclusion of others that may also be suitable.