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Crop residue decomposition in Minnesota biochar-amended plots

Weyers, S. L., Spokas, K. A.
ARS USDA Submissions 2014 v.5 pp. 499
Zea mays, agricultural soils, biochar, biodegradation, carbon, corn, long term effects, organic matter, soil amendments, soil organic matter, soil properties, wheat, wheat straw, Minnesota
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.