Liming Effects and Winter Wheat Yield Response in Biochar-Amended Agricultural Soils.

A growing number of studies in the literature demonstrate that the addition of biochar to agricultural soils has the potential to boost crop yields, though outcomes are far from uniform and understanding of the underlying mechanisms remains incomplete.  In particular, debate continues as to whether observed yield responses are adequately explained in the context of changes to basic soil chemical and physical properties (e.g. pH, water holding capacity), or whether more direct biotic interactions between biochar and plant or microbial communities (e.g. ethylene emissions, provision of microbial habitat in pore spaces) play a significant role.  A greenhouse experiment was conducted during the 2011 season to investigate the effect of biochar amendments on soil pH and the production of winter wheat (Triticum aestivum ‘Hatcher’).  Three agricultural soils of similar texture and chemical properties but different pH (ranging from 5 to 8) were collected, two locally in Colorado and the third from West Virginia.  The soils were amended with three biochars produced from different feedstocks and conversion processes (char-optimized gasification of pine wood, fast pyrolysis of corn stover, and TLUD gasification of wheat straw), and a lime treatment of equivalent acid-neutralizing capacity.  Grain and biomass yields were evaluated, and elemental and isotope analysis performed on tissues to monitor for changes in nitrogen nutrition and water use efficiency.  Analysis of results is ongoing, though preliminary results suggest that while each of the biochars did raise the pH of all three soils to a degree consistent with their laboratory-measured liming value, yield response was neutral or beneficial across all soils including the alkaline soil.  Ongoing analysis is focused on soil moisture dynamics, and it is hypothesized that changes to water holding capacity and drainage rates in the char-amended soils contributed to the positive results observed.