Corn and Soil Response to Biochar Application and Stover Harvest.

There is growing interest in the potential use of biochar soil applications to help mitigate potential negative effects of harvesting crop residues for bioenergy production on soil quality. Our objectives were to evaluate effects of a onetime biochar application on crop yields and soil properties at a Midwestern U.S.A. site where corn (Zea Mays) stover is being harvested. Lump hardwood biochar produced by slow pyrolysis at ~450oC was hammer milled to pass a 12 mm screen, surface applied (0, 9.8, and 18.4 Mg ha-1), and incorporated to 20 cm on 36 randomized 0.11 ha field plots in Boone County, Iowa in the fall of 2007. Corn and biomass yields were measured for the 2008-2012 crop years. During the first five years of the study, the 50 and 90% residue removal treatments significantly increased corn grain yields by 1.4 Mg Ha-1, averaged across all biochar treatments. The residue removal effects on yields were largest during years of stress due to excess moisture (2008 and 2010) and drought (2012), while no effect of residue removal was observed in 2011, a year with favorable climatic conditions. On average biochar applications significantly increased yields on the 0% residue removal plots by 1.7 Mg ha-1 but had no effect on grain yields for the 50% and 90% residue removal plots. The results suggest that in the short term biochar applications may help mitigate some, but not all, of the potential negative effects of residue harvest on soil quality.