References

Aitkenhead, Matt J, and Helaina IJ Black. 2018. Exploring the impact of different input data types on soil variable estimation using the ICRAF-ISRIC global soil spectral database.” Applied Spectroscopy 72 (2): 188–98. https://doi.org/10.1177/0003702817739013.
Ayres, Edward. 2019. “Quantitative Guidelines for Establishing and Operating Soil Archives.” Soil Science Society of America Journal 83 (4): 973–81. https://doi.org/10.2136/sssaj2019.02.0050.
Benedetti, F., and F. van Egmond. 2021. Global Soil Spectroscopy Assessment. Spectral soil data — Needs and capacities. Rome, Italy: FAO. https://doi.org/10.4060/cb6265en.
Böhner, J, T Blaschke, and L Montanarella. 2008. SAGA—Seconds Out, Vol. 19. Hamburg, Germany: Hamburger Beiträge zur Physischen Geographie und Landschaftsökologie.
Bremner, John M. 1996. “Nitrogen-Total.” In Methods of Soil Analysis: Part 3 Chemical Methods, 5:1085–1121. Wiley Online Library.
Brocca, Luca, Paolo Filippucci, Sebastian Hahn, Luca Ciabatta, Christian Massari, Stefania Camici, Lothar Schüller, Bojan Bojkov, and Wolfgang Wagner. 2019. SM2RAIN–ASCAT (2007–2018): global daily satellite rainfall data from ASCAT soil moisture observations.” Earth System Science Data 11 (4): 1583–1601. https://doi.org/10.5194/essd-11-1583-2019.
Chang, Cheng-Wen, David Laird, Maurice J Mausbach, and Charles R Hurburgh Jr. 2001. “Near-Infrared Reflectance Spectroscopy–Principal Components Regression Analyses of Soil Properties.” Soil Science Society of America Journal 65 (2): 480. https://doi.org/10.2136/sssaj2001.652480x.
Chen, Tianqi, Tong He, Michael Benesty, Vadim Khotilovich, Yuan Tang, Hyunsu Cho, and others. 2015. Xgboost: extreme gradient boosting.” CRAN R-Project. https://cran.r-project.org/package=xgboost.
Demattê, José AM, José Lucas Safanelli, Raul Roberto Poppiel, Rodnei Rizzo, Nélida Elizabet Quiñonez Silvero, Wanderson de Sousa Mendes, Benito Roberto Bonfatti, et al. 2020. “Bare Earth’s Surface Spectra as a Proxy for Soil Resource Monitoring.” Scientific Reports 10 (1): 1–11. https://doi.org/10.1038/s41598-020-61408-1.
Elrashidi, MA, D Hammer, CA Seybold, RJ Engel, R Burt, and P Jones. 2007. “Application of Equivalent Gypsum Content to Estimate Potential Subsidence of Gypsiferous Soils.” Soil Science 172 (3): 209–24.
Friedman, Jerome, Trevor Hastie, and Robert Tibshirani. 2010. Regularization Paths for Generalized Linear Models via Coordinate Descent.” Journal of Statistical Software 33 (1): 1–22. https://doi.org/10.18637/jss.v033.i01.
Garrity, Dennis, and Prem Bindraban. 2004. A Globally Distributed Soil Spectral Library Visible Near Infrared Diffuse Reflectance Spectra. Nairobi, Kenya: ICRAF (World Agroforestry Centre) / ISRIC (World Soil Information) Spectral Library. https://doi.org/10.34725/DVN/MFHA9C.
Grossman, RB, and TG Reinsch. 2002. “2.1 Bulk Density and Linear Extensibility.” In Methods of Soil Analysis: Part 4 Physical Methods, 5:201–28. Wiley Online Library.
Helling, Charles S, G Chesters, and RB Corey. 1964. “Contribution of Organic Matter and Clay to Soil Cation-Exchange Capacity as Affected by the pH of the Saturating Solution.” Soil Science Society of America Journal 28 (4): 517–20.
Hengl, Tomislav, Matthew AE Miller, Josip Križan, Keith D Shepherd, Andrew Sila, Milan Kilibarda, Ognjen Antonijević, et al. 2021. “African Soil Properties and Nutrients Mapped at 30 m Spatial Resolution Using Two-Scale Ensemble Machine Learning.” Scientific Reports 11 (1): 1–18. https://doi.org/10.1038/s41598-021-85639-y.
Hong, Yongsheng, Muhammad Abdul Munnaf, Angela Guerrero, Songchao Chen, Yaolin Liu, Zhou Shi, and Abdul Mounem Mouazen. 2022. “Fusion of Visible-to-Near-Infrared and Mid-Infrared Spectroscopy to Estimate Soil Organic Carbon.” Soil and Tillage Research 217: 105284. https://doi.org/10.1016/j.still.2021.105284.
Jensen, JL, BT Christensen, P Schjønning, CW Watts, and LJ Munkholm. 2018. “Converting Loss-on-Ignition to Organic Carbon Content in Arable Topsoil: Pitfalls and Proposed Procedure.” European Journal of Soil Science 69 (4): 604–12. https://doi.org/10.1111/ejss.12558.
Kuhn, Max, Steve Weston, Chris Keefer, and Nathan Coulter. 2012. “Cubist Models for Regression.” CRAN R-Project. https://cran.r-project.org/package=Cubist.
Lei, Tong, and Da-Wen Sun. 2022. “Achieving Joint Calibration of Soil Vis-NIR Spectra Across Instruments, Soil Types and Properties by an Attention-Based Spectra Encoding-Spectra/Property Decoding Architecture.” Geoderma 405: 115449. https://doi.org/10.1016/j.geoderma.2021.115449.
Loeppert, Richard H, Donald L Suarez, and others. 1996. “Carbonate and Gypsum.” In Methods of Soil Analysis. Part 3 Chemical Methods, 3:437–74. Wiley Online Library.
McLean, EO. 1983. Soil pH and lime requirement.” In Methods of Soil Analysis: Part 2 Chemical and Microbiological Properties, 9:199–224. Wiley Online Library.
Miller, Robert O, and David E Kissel. 2010. Comparison of soil pH methods on soils of North America.” Soil Science Society of America Journal 74 (1): 310–16. https://doi.org/10.2136/sssaj2008.0047.
Nelson, DW, and L_E Sommers. 1983. “Total Carbon, Organic Carbon, and Organic Matter.” In Methods of Soil Analysis: Part 2 Chemical and Microbiological Properties, 9:539–79. Wiley Online Library.
Orgiazzi, Alberto, Cristiano Ballabio, Panagiotis Panagos, Arwyn Jones, and Oihane Fernández-Ugalde. 2018. LUCAS Soil, the largest expandable soil dataset for Europe: a review.” European Journal of Soil Science 69 (1): 140–53. https://doi.org/10.1111/ejss.12499.
Sanderman, Jonathan, Kathleen Savage, and Shree RS Dangal. 2020. Mid-infrared spectroscopy for prediction of soil health indicators in the United States.” Soil Science Society of America Journal 84 (1): 251–61. https://doi.org/10.1002/saj2.20009.
Summerauer, L., P. Baumann, L. Ramirez-Lopez, M. Barthel, M. Bauters, B. Bukombe, M. Reichenbach, et al. 2021. “The Central African Soil Spectral Library: A New Soil Infrared Repository and a Geographical Prediction Analysis.” SOIL 7 (2): 693–715. https://doi.org/10.5194/soil-7-693-2021.
Sumner, Malcolm E, and William P Miller. 1996. “Cation Exchange Capacity and Exchange Coefficients.” In Methods of Soil Analysis: Part 3 Chemical Methods, 5:1201–29. Wiley Online Library.
Testing, American Society for, Materials. Committee D18 on Soils, Rock, American Society for Testing, Materials. Subcommittee D18.07 on Identification, Classification of Soils, and ASTM International. 2006. Standard Practice for Description and Identification of Soils (Visual-Manual Procedure). Philadelphia, PA: ASTM International.
Thomas, GW. 1982. “Exchangeable Cations. P. 159–165. AL Page Et Al.(ed.) Methods of Soil Analysis. Part 2. Agron. Monogr. 9. ASA and SSSA.” In Exchangeable Cations. P. 159–165. In AL Page Et Al.(ed.) Methods of Soil Analysis. Part 2. 2nd Ed. Agron. Monogr. 9. Madison, WI: ASA; SSSA.
USDA NRCS. 2019. Soil Survey Field and Laboratory Methods Manual - Soil Survey Investigations Report No. 51 (Version 2) Issued 2014. Lincoln, Nebraska: U.S. Department of Agriculture, Natural Resources Conservation Service.
Vagen, Tor-Gunnar, Leigh Ann Winowiecki, Luseged Desta, Ebagnerin Jerome Tondoh, Elvis Weullow, Keith Shepherd, and Andrew Sila. 2020. Mid-Infrared Spectra (MIRS) from ICRAF Soil and Plant Spectroscopy Laboratory: Africa Soil Information Service (AfSIS) Phase I 2009-2013. World Agroforestry - Research Data Repository. https://doi.org/10.34725/DVN/QXCWP1.
Vohland, Michael, Bernard Ludwig, Michael Seidel, and Christopher Hutengs. 2022. Quantification of soil organic carbon at regional scale: Benefits of fusing vis-NIR and MIR diffuse reflectance data are greater for in situ than for laboratory-based modelling approaches.” Geoderma 405: 115426. https://doi.org/10.1016/j.geoderma.2021.115426.
Wadoux, A. M. J. C., B. Malone, A. B. McBratney, M. Fajardo, and B. Minasny. 2021. Soil Spectral Inference with R: Analysing Digital Soil Spectra Using the R Programming Environment. Progress in Soil Science. Springer International Publishing.
Wijewardane, Nuwan K, Yufeng Ge, Skye Wills, and Zamir Libohova. 2018. Predicting physical and chemical properties of US soils with a mid-infrared reflectance spectral library.” Soil Science Society of America Journal 82 (3): 722–31. https://doi.org/10.2136/sssaj2017.10.0361.
Wright, Marvin N, and Andreas Ziegler. 2017. ranger: A Fast Implementation of Random Forests for High Dimensional Data in C++ and R.” Journal of Statistical Software 77 (1): 1–17. https://doi.org/10.18637/jss.v077.i01.