Sugar Maple (Acer saccharum) Biochar As a Soil Amendment for Soybean (Glycine max L. Merr.) Crops and Its Effect On Biological Nitrogen Fixation (BNF) and Nodulation.

Sugar Maple (Acer saccharum) Biochar as a soil amendment for Soybean (Glycine max L. Merr.) crops: effect on Biological Nitrogen Fixation (BNF) and nodulation. Mitalie M. Makhani and Marney E. Isaac, University of Toronto Scarborough, Toronto, ON, Canada Biochar has been hailed as the black gold of agriculture. The potential for carbon sequestration, improved nutrient retention capacities and overall soil fertility make biochar a valuable resource. This study aims to determine the effect of biochar additions on biological nitrogen fixation (BNF) and nodulation in a leguminous crop species. Soybeans (Glycine max L. Merr.) were grown for four weeks under three different shade levels (0%, 22% and 50%) after which they were transplanted into rhizoboxes. Rhizoboxes contained a P-sufficient topsoil with sugar maple (Acer saccharum) biochar additions or no biochar. After two weeks of contact between the soybeans and biochar amended or non-amended soils in rhizoboxes, soils were analyzed for extractable nitrates and orthophosphates. Biomass production and allocation was also assessed. Across all shade levels there was a significant increase in orthophosphate between biochar and no biochar application (P = 0.0327) with a mean of 9.37 ± 0.582a and 7.91 ± 0.143b, respectively. Previous studies have reported an increase in BNF with biochar as a result of greater bioavailability of boron and molybdenum (essential for the nitrogenase enzyme complex). It is expected that soybeans grown on biochar-amended soil will have higher overall biomass production (roots, stem, and leaves) and greater P bioavailability as a result of higher BNF. Soybeans grown in biochar amended soil treatments are expected to rely more heavily on BNF, as extractable nitrates are expected to be low in biochar amended soils, due to high C:N ratios. This study hopes to serve as a platform for the use of biochar as a soil amendment for larger regional scale applications for soybean crop production in Southern Ontario.