School of Earth, Environmental, and Marine Sciences Faculty Publications and Presentations

Toward a Better Assessment of Biochar–Nitrous Oxide Mitigation Potential at the Field Scale

Document Type

Article

Publication Date

3-2-2017

Abstract

Through meta-analysis, we synthesize results from field studies on the effect of biochar application on N2O emissions and crop yield. We aimed to better constrain the effect of biochar on N2O emissions under field conditions, identify significant predictor variables, assess potential synergies and tradeoffs between N2O mitigation and yield, and discuss knowledge gaps. The response ratios for yield and N2O emissions were weighted by one of two functions: (i) the inverse of the pooled variance or (ii) the inverse of number of observations per field site. Significant emission reductions were observed when weighting by the inverse of the pooled variance (−18.1 to −7.1%) but not when weighting by the number of observations per site (−17.1 to +0.8%), thus revealing a bias in the existing data by sites with more observations. Mean yield increased by 1.7 to 13.8%. Our study shows yield benefits but no robust evidence for N2O emission reductions by biochar under field conditions. When weighted by the inverse of the number of observations per site, N2O emission reductions were not significantly affected by cropping system, biochar properties of feedstock, pyrolysis temperature, surface area, pH, ash content, application rate, or site characteristics of N rate, N form, or soil pH. Uneven coverage in the range of these predictor variables likely underlies the failure to detect effects. We discuss the need for future biochar field studies to investigate effects of fertilizer N form, sustained and biologically relevant changes in soil moisture, multiple biochars per site, and time since biochar application.

Comments

Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Publication Title

Journal of Environmental Quality

DOI

https://doi.org/10.2134/jeq2016.10.0396

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