Climate mitigation through soil amendments: quantification, evidence, and uncertainty.

Soil amendments are a broad class of materials that enhance physical, chemical or biological characteristics in croplands, pastures, or rangelands. While organic soil amendments such as manure, mulch and seaweed have well established agronomic benefits, there has been renewed private and governmental interest in quantifying and incentivizing their role in mitigating climate change. Likewise, biostimulants and biopesticides, which are intended to target specific plant or microbial processes, are emerging with claims of improved soil health, crop yields, soil organic carbon sequestration, and greenhouse gas emission reductions. We conducted a literature review to address the climate mitigation potential of organic soil amendments, including biostimulants and biopesticides. In doing so, we identify three elements of climate mitigation through the use of soil amendments: soil organic carbon sequestration, soil greenhouse gas emission reductions, and life cycle emission reductions. We review common soil amendment classes in detail, addressing the empirical evidence (or lack thereof) in which they meet these three elements of climate mitigation. We conclude by suggesting priorities for government and private investment. [ABSTRACT FROM AUTHOR]