Crop Yield Responses to a Hardwood Biochar Across Varied Soils and Climate Conditions.

Biochars applied to soil for crop yield improvements have produced mixed results.  The assorted crop yield responses may be linked to employing biochars with diverse chemical and physical characteristics.  To clarify if biochars can improve crop yields, it may be prudent to evaluate one biochar type under different soil/climate conditions.  Here, we conducted a multi-year (2008 to 2013) field performance evaluation at six locations encompassing the USA using a hardwood biochar to improve corn (Zea mays) and sorghum (Sorghum bicolor) stand counts, grain, and biomass yields.  Wood waste was pyrolyzed between 500 to 600°C to produce the hardwood biochar.  The biochar had a pH of 5.59, ash content of 14.2%, and contained macronutrients (N, K, P, etc.).  In general, biochar was applied to triplicate plots at 17.4 to 22.4 Mg/ha.  Additionally, both wet and dry animal manure sources were applied, manure mixed with biochar was also applied, and plots treated with inorganic fertilizer alone served as controls.  Results for sorghum were inclusive due to drought.  For corn, however, pooling results across five locations and years, we found no significant effect of hardwood biochar on stand counts, grain yields, and stover yields (minus grain wt.).  We conclude that this hardwood biochar within the timeframe of this experiment was not a suitable soil amendment to improve corn productivity.  On the other hand, it did not negatively impact corn production.