The Brazilian Soil Spectral Service (BraSpecS): A User-Friendly System for Global Soil Spectra Communication

Abstract

Although many Soil Spectral Libraries (SSLs) have been created globally, these libraries still have not been operationalized for end-users. To address this limitation, this study created an online Brazilian Soil Spectral Service (BraSpecS). The system was based on the Brazilian Soil Spectral Library (BSSL) with samples collected in the Visible–Near–Short-wave infrared (vis–NIR–SWIR) and Mid-infrared (MIR) ranges. The interactive platform allows users to find spectra, act as custodians of the data, and estimate several soil properties and classification. The system was tested by 500 Brazilian and 65 international users. Users accessed the platform (besbbr.com.br), uploaded their spectra, and received soil organic carbon (SOC) and clay content prediction results via email. The BraSpecS prediction provided good results for Brazilian data, but performed variably for other countries. Prediction for countries outside of Brazil using local spectra (External Country Soil Spectral Libraries, ExCSSL) mostly showed greater performance than BraSpecS. Clay R2 ranged from 0.5 (BraSpecS) to 0.8 (ExCSSL) in vis–NIR–SWIR, but BraSpecS MIR models were more accurate in most situations. The development of external models based on the fusion of local samples with BSSL formed the Global Soil Spectral Library (GSSL). The GSSL models improved soil properties prediction for different countries. Nevertheless, the proposed system needs to be continually updated with new spectra so they can be applied broadly. Accordingly, the online system is dynamic, users can contribute their data and the models will adapt to local information. Our community-driven web platform allows users to predict soil attributes without learning soil spectral modeling, which will invite end-users to utilize this powerful technique.

Transferability of a large mid‐infrared soil spectral library between two Fourier‐transform infrared spectrometers

“…As regional and global efforts to share large spectral libraries and build spectroscopy‐based estimation services are increasing (Demattê et al., 2022; Shepherd et al., 2022), it is critical to understand when calibration transfer is necessary. Harmonizing spectral collection to be consistent with the primary instrument may avoid the need for calibration transfer but given the diversity in instrument types and set‐ups (Benedetti & van Egmond, 2021), it is likely that the need for calibration transfer will at least have to be tested on a case‐by‐case basis.…”

In‐field soil spectroscopy in Vis–NIR range for fast and reliable soil analysis: A review

“…As moisture content will vary between samples—and thus also the moisture effects—an additional dimension is added for moist samples, making calibration work overwhelming. Despite the challenges involved, applying SSL‐based calibrations on field sampled spectra appears as the most realistic and reasonable way forward; several large SSLs are already built and under development (Dangal et al, 2019; Demattê et al, 2022). However, the challenges dealing with discrepancies between field and laboratory spectra need to be addressed.…”

A Spectral Transfer Function to Harmonize Existing Soil Spectral Libraries Generated by Different Protocols

“…Te accuracies of the harmonization platform of Demattê et al [12] varied in the OC and texture predictions, as some examination cases showed good accuracies and others did not. Indeed, mathematical manipulations can contribute to relating SSLs from diferent laboratories, but it is still necessary to harmonize the initial "raw" data (nonpreprocessed refectance spectra) of the SSLs.…”

“…To harmonize the global SSL (collected from SSLs using diferent protocols), Viscarra Rossel et al [1] rectifed noise efects using wavelet transformation, following the approach of Viscarra Rossel and Lark [11] to improve the performance of spectral-based models for soil properties characterization. Te frst online spectral service was recently published by Demattê et al [12], who provided a user-friendly system for global soil spectra communication based on the BSSL and tested it with the spectra from 65 countries.…”