SUSTAINABLE CROPPING SYSTEMS FOR IRRIGATED SPECIALTY CROPS AND BIOFUELS
Location: Vegetable and Forage Crops Production Research
Title: Influence of Biochar on Soil pH, Water Holding Capacity, Nitrogen and Carbon Dynamics
Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 20, 2011
Publication Date: June 23, 2011
Citation: Streubel, J.D., Collins, H.P., Garcia-Perez, M., Tarara, J.M., Granatstein, D., Kruger, C.E. 2011. Influence of Biochar on Soil pH, Water Holding Capacity, Nitrogen and Carbon Dynamics. Soil Science Society of America Journal. 75: 1402-1413.
Interpretive Summary: Biochar, a typical co-product of biomass pyrolysis is being promoted for its potential large-scale and low-cost carbon sequestration in soil. Much of the knowledge regarding biochar derives from studies of Terra Preta soils in the Amazonian basin, where biochar-like materials appear to have substantially altered soil physical and chemical properties and led to long-lasting carbon storage and improved crop production. How this material might impact agricultural soils within temperate regions is largely unknown, Validation of biochar as a beneficial soil amendment and carbon sink would add important economic value to the pyrolysis process and spur adoption and further waste utilization. Bio-chars from four waste feedstocks (pine chips, softwood bark, grass seed straw anaerobic digested manure fiber) were produced with a at four different temperatures (350, 425, 500 and 600oC)and evaluated for their influence on the soil properties; pH, buffering capacity, cation exchange capacity, water retention curves, and nitrogen and carbon sequestration potentials of five soil types.
The recent focus of biochar as a soil amendment for improving soil physical-chemical properties and carbon sequestration has revealed knowledge gaps in the research covering different feedstocks in various soil types. Biochars made from four feedstocks (wood pellets [Pseudotsuga menziesii], softwood bark [Pseudotsuga menziesii], switchgrass [Panicum virgatum] straw, anaerobic digester fiber) produced by pyrolysis at 500oC were evaluated for pH, cation exchange capacity, water holding capacity, elemental content, and C and N mineralization potentials in five soils. Soils were amended with four rates (0 9.8, 19.5 and 39.0 Mg ha-1) of the various biochars and evaluated under laboratory incubation. The C content of chars derived from the herbaceous feedstocks was 60 to 67% whereas that of the woody feedstocks was >75%. Biochars, despite their origin, raised the pH of all soil types 0.1 to 0.9 units with the greatest impact on a Quincy sand soil. The chars increased soil carbon and produced mixed results on water holding capacity dependent on soil and char. Nitrogen mineralization rates decreased in three of the five soils across all feedstocks with the remaining two soils showing various increases or no change from application of the switchgrass and anaerobic fiber derived chars. The biochar was stable in the soil after 225-d incubation; there was a significant correlation (r'90) between predicted and actual soil carbon after biochar additions regardless of feedstock or soil type. These differences were attributed to the biochar’s individual elemental and structural characteristics.