Commercial scale agricultural biochar field trial in Québec, Canada over two years: effects of biochar on soil fertility, biology and crop productivity and quality

A commercial scale biochar field trial was established on a farm in Québec, Canada in May 2008. A very fine, commercially available biochar from fast pyrolysis of wood waste was applied as received from the manufacturer using standard farm machinery. The target application rate was 5.6 t/ha, but an estimated 30% of the material was wind-blown and lost during handling, transport to the field, soil application and incorporation. This resulted in an estimated 3.9 t/ha biochar application. Biochar was applied on a clay loam soil in a single, 1,000 m swath and compared to an adjacent, unamended control swath, thus this is not a standard replicated experiment. Soybean was grown in 2008 and mixed forage species in 2009, and a large dataset was gathered including monthly data on soil physical parameters, soil chemical fertility, soil microand macrofauna, crop morphology, quality and yield. Yield increases in soybean averaged 19% over the control, and forage biomass was doubled by biochar application, compared to the control. In soybean, yield improvements arose from greater plant population density, as opposed to greater seed production per plant. Yield differences cannot clearly be attributed to chemical soil fertility differences among treatments. Total and available P are very high on this soil which is considered to be P-saturated. Biochar-amended plots had lower total P contents, and this cannot be fully explained with available data. Surface soil infiltration was greater when biochar had been applied, but no differences were found in soil temperature, moisture content, and resistance to penetration. The number of nodules per soybean plant was not affected by the biochar treatment, but root colonization by ectomycorrhizae in the forage crop was greater when biochar was applied. Earthworm density was generally greater with biochar, and data on fungal and microbial grazers, and microbial and fungal biomass seem to support the hypothesis that biochar can serve as a refuge for soil microbes. Total soil carbon, soil respiration and potential organic matter mineralization were not measurably different in the biochar-amended plot. This is the first report on results from commercial scale biochar field trials in Canada.