Can Low-Cost, Handheld Spectroscopy Tools Coupled with Remote Sensing Accurately Estimate Soil Organic Carbon in Semi-Arid Grazing Lands?

Abstract

Soil organic carbon influences several landscape ecological processes, and soils are becoming recognized as a mechanism to mitigate the negative impacts of climate change. There is a need to define methods and technologies for addressing soils’ spatial variability as well as the time and cost of sampling soil organic carbon (SOC). Visible and near-infrared spectroscopy have been suggested as a sampling tool to reduce inventory cost. We sampled nineteen ranch properties totaling 17,347 ha across Oklahoma and Texas in 2019 to evaluate the effectiveness and accuracy of a handheld reflectometer (Our Sci, Ann Arbor, MI, USA) (370–940 nm) and existing remote sensing approaches to estimate SOC in semi-arid grazing lands. Our data suggest that the Our Sci Reflectometer estimated soil organic carbon with a precision of approximately (±0.3% SOC); however, it was least accurate at higher carbon concentrations. The Our Sci reflectometer, although consistently accurate at lower SOC concentrations, was still less accurate than a model built using only remote sensing and digital soil map data as predictors. Combining the two data sources was the most accurate means of determining SOC. Our results indicated that the Our Sci handheld Vis-NIR reflectometer tested may have only limited applications for reducing inventory costs at scale.

The use of visible and near‐infrared spectroscopy for in‐situ characterization of agricultural soil fertility: A proposition of best practice by comparing scanning positions and spectrometers

“…The NEO spectrometer became available recently, and several authors have used it or other MEMS‐based spectrometers in the context of soil analysis for OC, texture, pH and nutrient analysis as well as in comparative studies with research‐grade spectrometers (Angeletti da Fonseca et al, 2022; Goodwin et al, 2022; Karyotis et al, 2021; Ng et al, 2020; Pasquini & Hespanhol, 2021; Sharififar et al, 2019; Tang et al, 2020; Thomas et al, 2021). Overall, it appears that the NEO spectrometer, as other low‐cost MEMS instruments, are less performing than the full‐range spectrometers, but that they show a potential for future applications (Karyotis et al, 2021; Tang et al, 2020; Thomas et al, 2021).…”

Rapid soil harvesting using a novel soil auger system for farm‐scale soil carbon estimates

“…heterogeneity of soil carbon is greater than bulk density, one approach to efficiently measure stocks is to take soil carbon samples at greater spatial resolution (i.e., more dense sampling) than bulk density samples (Bettigole et al, 2023;Don et al, 2007). Considerations such as sampling density and frequency, sample compositing, and sampling depth are often factored into measuring soil C concentrations in order to minimize time and cost while maintaining the required level of accuracy for the project (Bettigole et al, 2023;Goodwin et al, 2022;Smith et al, 2020;Stanley et al, 2023). One component of sampling that is often not considered is the method of harvesting soils, despite the potential time-cost associated with high sampling densities required for soil C sampling.…”