Corn and soil response to biochar application and stover harvest

Authors: ROGOVSKA, NATALIA - Iowa State University; LAIRD, DAVID - Iowa State University; Karlen, Douglas

Submitted to: Field Crops Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/19/2015
Publication Date: 1/12/2016
Publication URL: https://handle.nal.usda.gov/10113/5262965
Citation: Rogovska, N., Laird, D.A., Karlen, D.L. 2016. Corn and soil response to biochar application and stover harvest. Field Crops Research. 187:96–106.

Interpretive Summary: Developing commercial-scale cellulosic industries may provide a boost to rural economies, create jobs, and reduce dependence on imported oil; but if crop residue, the primary feedstock for these industries, is not managed appropriately, soil degradation and environmental risks could be severe. One strategy for developing these industries is to use a pyrolysis (high-temperature in the absence of oxygen) conversion process which creates biochar as a co-product. Returning the biochar to harvest sites could help restore soil carbon levels and thus prevent soil degradation if stover harvest rates were too high or initial soil carbon levels below the optimum level for a particular soil type. This research presents information on both crop and soil response to two biochar application rates on soils in central Iowa, U.S.A. Our results suggest that in the short term biochar applications may help mitigate some, but not all, of the potential negative effects of excessive residue harvest on soil quality. Therefore, some crop residue should be left on the surface even for soils that receive high doses of biochar. This information will be of interest to scientists, farmers, conservationists, and those striving to develop sustainable, cellulosic bioenergy and bio-product conversion facilities.

Technical Abstract: 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 ~450°C 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. Soil properties were measured in summer 2010 three years after the biochar application and after two stover harvests (0, ~50 and ~90% of above ground residue). Corn and biomass yields were measured for the 2008-2012 crop years. Biochar applications increased total carbon (TC) of soils by about 0.5% and soil pH by about 0.5 pH units but had no significant effect on soil total nitrogen (TN), soil test nutrients, bulk density (BD), aggregate stability or effective cation exchange capacity (ECEC). Residue removal had no significant effect on TC, TN, ECEC, and soil test nutrients with the exception of Zn and S. The 90% residue removal treatment significantly reduced wet aggregate mean weight diameter by 13% relative to the 0% residue harvest treatment. 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.