Predicting SOC using soil spectroscopy

Infrared spectroscopy (IR) is an established technology for rapid, non-destructive characterization of the composition of materials based on the interaction of electromagnetic energy with matter.

IR is now routinely used for analyses of a wide range of materials in laboratory and process control applications in agriculture, food and feed technology, geology and biomedicine (Shepherd and Walsh, 2004; 2007).

IR enables soil-sampling density (samples per unit area) to be greatly increased with little increase in analytical cost.

The near and mid infrared region of the electromagnetic wage were investigated for non-destructive analyses of soil organic carbon in western Kenya. The results indicate hat Both NIR and MIR strongly predict carbon concentration with some bias for higher carbon values (Figure 1). However, MIR performed better than NIR to estimate SOC concentration.

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Figure 1. Partial least squares (PLS) regression analysis for: (a) NIR and (b) MIR cross-validation using a leave one out procedure and (c) density plot showing the reference data using the thermal oxidation and the predicted values using NIR and MIR spectroscopy

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Shepherd, K.D., and Walsh, M.G. 2004. Diffuse reflectance spectroscopy for rapid soil analysis, In Lal, R., ed. Encyclopedia of Soil Science. Marcel Dekker Inc., New York.

Shepherd, K.D. and Walsh, M.G. 2007. Infrared spectroscopy-enabling an evidence-based diagnostic surveillance approach to agricultural and environmental management in developing countries. Journal of Near Infrared Spectroscopy 15:1-19.