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

Abstract

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.

Desorption of adsorbed ammonium in some Gypsiferous soils, Tikrit Governorate, Iraq

“…Gypsiferous soil is a type of soil that is characterized by a low to high concentration of di-hydrated calcium sulphate, which may range between 5 to more than 95% [1] . This type of soil is found in arid and semi-arid areas, and is poor in organic matter content [2] . These soils are vulnerable to degradation, especially in overuse cases; however, they can be productive with appropriate practices of management [3,4] .…”

Carbon Stock Assessment in Gypsum-Bearing Soils: The Role of Subsurface Soil Horizons

“…According to FAO [26], SOC concentration values in such soils (hereafter expressed as "oxidizable organic carbon determined by acid-dichromate digestion" [27]) generally ranges from 0.2 to 0.6% in surface horizons to less than 0.1% in subsurface layers. However, local studies show higher values, also in subsurface soil horizons; regarding Eastern Spain, soils from gypsiferous parent materials under xeric and aridic SMRs show mean SOC values slightly over 1% in surface A horizons of rainfed croplands [29,30]. Under shrublands, SOC values range from 1-3% in surface horizons and 0.2-0.3% in C horizons [10].…”

“…Although gypseous soils can be moderately productive with adequate management practices, they are especially vulnerable to degradation [30], which is directly related to SOC decrease [34]. Erosion processes of gypseous soils can be serious because of poor aggregation, which is at least partially influenced by low organic matter.…”

Challenges of Biochar Usages in Arid Soils: A Case Study in the Kingdom of Saudi Arabia

“…These soils exhibit low soil aggregation and can, therefore, be subjected easily to wind erosion [6]. Moreover, secondary minerals may dominate in such soils like calcite and gypsum [1], and these minerals can significantly diminish soil fertility [7,8]. Another important threat that faces agricultural sustainability in arid sand semiarid soils is soil salinity [9].…”