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Dryad

Microwave and millimeter wave signals reflectance of soil carbon content

Abstract

Agricultural and forestry biomass can be converted to biochar through pyrolysis gasification, making it a significant carbon source for soil. Applying biochar to soil is a carbon-negative process that helps combat climate change, sustain soil biodiversity, and regulate water cycling. However, quantifying soil carbon content conventionally is time-consuming, labor-intensive, imprecise, and expensive, making it difficult to accurately measure in-field soil carbon's effect on storage water and nutrients. To address this challenge, for the first time, we report on extensive lab tests demonstrating non-intrusive methods for sensing soil carbon and related smart biochar applications, such as differentiating between biochar types from various biomass feedstock species, monitoring soil moisture, and biochar water retention capacity using portable microwave and millimeter wave sensors and machine learning. The datasets provide details on the microwave and millimeter wave reflectance signals. We validated our quantification method using supervised machine learning algorithms by collecting real soil mixed with known biochar contents in the field.