Submitted to: Solid Earth
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/6/2014
Publication Date: 6/11/2014
Publication URL: https://handle.nal.usda.gov/10113/58917
Citation: Weyers, S.L., Spokas, K.A. 2014. Crop residue decomposition in Minnesota biochar-amended plots. Solid Earth. 5:499-507.
Interpretive Summary: Application of biochar, a black carbon, may be beneficial for soil processes. However, large-scale impacts on functional processing of surface residues needs further study. Researchers at the USDA-ARS labs in Morris and St. Paul, Minnesota, evaluated decomposition of wheat straw litter over 14-wks in plots to which multiple types of biochar and organic amendments were applied. Decomposition rates in most biochar and organic amended plots were higher than a control. The highest decomposition was found in plots where hardwood-derived biochar produced by fast pyrolysis was applied. Decomposition was slowest in plots with a high-level application of a fast pyrolysis macadamia nut-derived biochar, which may have increased production of ethylene. These findings provide additional insight and direction in the evaluation of biochar as a soil amendment. These results are significant to farmers, researchers and policy makers and will assist the development of management practices for biochar application which may be useful for the improvement of soil function and C-sequestration.
Technical Abstract: Biochar, a black carbon substance, can be a beneficial soil amendment to improve soil properties and sequester C. Positive and negative priming effects on soil organic matter (SOM) are as wide ranging as the feedstocks and pyrolysis platforms used to create biochar. Impacts of biochar application on the microscale of SOM processing are well studied, but impacts on decomposition of coarse particular organic matter, such as crop residue, have not been widely addressed. The objectives of this study were to evaluate potential effects of biochars made with different feedstocks and pyrolysis platforms and applied at different rates on decomposition of wheat straw. Litterbags containing wheat straw material were buried below the soil surface in a continuous-corn cropped field that had received thirteen different organic and biochar amendments, which had weathered in the field for 2.5-yr prior to start of this study. Though statistical associations may have been weak (P-values up to 0.06), the decomposition trends observed supported findings that fast pyrolysis platforms may create biochars with active components that positively prime soil nutrient turnover processes. This positive priming appears to have additional impacts that resulted in increased decomposition rates of wheat residues. The results demonstrate that initial short-term priming impacts on soil carbon turnover may have long-term effects on the decomposer community responsible for processing coarse particulate litter material and maintaining nutrient cycling processes in soil.