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Open AccessArticle

Estimating Soil Organic Carbon in Agricultural Gypsiferous Soils by Diffuse Reflectance Spectroscopy

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Geology and Geochemistry Department, Faculty of Sciences, Autonomous University of Madrid, Calle Francisco Tomás y Valiente, 7, 28049 Madrid, Spain
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Departamento de Investigación Aplicada y Extensión Agraria, Instituto Madrileño de Investigación y Desarrollo Rural, Agrario y Alimentario (IMIDRA), Finca El Encín. Autovía A-2 km 38.2, 28800 Alcalá, Spain
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Author to whom correspondence should be addressed.
Water 2020, 12(1), 261; https://doi.org/10.3390/w12010261 (registering DOI)
Received: 18 December 2019 / Revised: 9 January 2020 / Accepted: 13 January 2020 / Published: 16 January 2020
Contents of soil organic carbon (SOC), gypsum, CaCO3, and quartz, among others, were analyzed and related to reflectance features in visible and near-infrared (VIS/NIR) range, using partial least square regression (PLSR) in ParLes software. Soil samples come from a sloping olive grove managed by frequent tillage in a gypsiferous area of Central Spain. Samples were collected in three different layers, at 0–10, 10–20 and 20–30 cm depth (IPCC guidelines for Greenhouse Gas Inventories Programme in 2006). Analyses were performed by C Loss-On-Ignition, X-ray diffraction and water content by the Richards plates method. Significant differences for SOC, gypsum, and CaCO3 were found between layers; similarly, soil reflectance for 30 cm depth layers was higher. The resulting PLSR models (60 samples for calibration and 30 independent samples for validation) yielded good predictions for SOC (R2 = 0.74), moderate prediction ability for gypsum and were not accurate for the rest of rest of soil components. Importantly, SOC content was related to water available capacity. Soils with high reflectance features held c.a. 40% less water than soils with less reflectance. Therefore, higher reflectance can be related to degradation in gypsiferous soil. The starting point of soil degradation and further evolution could be established and mapped through remote sensing techniques for policy decision making. View Full-Text
Keywords: VIS/NIR spectrometry; desertification; erosion; Spain; olive orchards VIS/NIR spectrometry; desertification; erosion; Spain; olive orchards
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Marques, M.J.; Álvarez, A.M.; Carral, P.; Esparza, I.; Sastre, B.; Bienes, R. Estimating Soil Organic Carbon in Agricultural Gypsiferous Soils by Diffuse Reflectance Spectroscopy. Water 2020, 12, 261.

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