Common‐Mode Rejection Shifted‐Excitation Raman Difference Spectroscopy (CMR‐SERDS) Preserves Broad Structure Predictive of Soil Organic Carbon

ABSTRACT

Large‐area soil organic carbon (SOC) measurements provide information for advancing soil health, optimizing agricultural productivity, and helping mitigate climate change; however, conventional soil analysis methods remain difficult to scale. Raman spectroscopy offers high‐throughput molecular information, but matrix effects and strong fluorescence interference limit its applicability to soil analysis. Here, we combine shifted excitation Raman difference spectroscopy (SERDS) with machine learning and signal processing to overcome these limitations, as demonstrated by the analysis of more than 900 geographically diverse North American soils. This work introduces common‐mode rejection (CMR), a physics‐motivated preprocessing method that follows the central SERDS principle by removing the broad background shared by paired shifted‐excitation measurements while preserving the noncommon component. Unlike conventional methods, such as asymmetric least squares (ALS) background subtraction, CMR avoids dataset‐specific manual tuning of the baseline. This method is also robust to multiplicative scaling and additive offset differences between paired spectra. CMR preserves a reproducible, broad excitation‐dependent spectral component that contributes materially to prediction. Multivariate regression models trained by CMR‐SERDS spectra afforded a 16% gain in coefficient of determination, R , and a 28% reduction in root mean squared error, RMSE, compared with SERDS spectra preprocessed by ALS to yield flat baselines. These results show that parametric background correction algorithms, deployed aggressively to produce cosmetically flattened baselines, remove analytically useful information and establish CMR‐SERDS as a robust, interpretable, and transferable framework for high‐throughput SOC analysis, and suggest broader relevance to Raman measurements acquired under strong background interference.