Abstract
The presence of iron oxides may provide a sensitive indicator of the effects of cropping practices on coffee plantations. Authors characterized the mineral phases present in soil A horizons at three different farms located in the Department of Tolima within the regions of Líbano and Villahermosa. Our analysis includes X-ray diffraction, Mössbauer spectroscopy, and remote sensing to discriminate the distribution of the different magnetic mineral phases. X-ray diffraction was used to identify the mineralogical properties of iron oxide such as hematite, goethite, and ferrihydrite (Fh), as well as tectosilicate minerals such as albite and sanidine. Mössbauer spectroscopy results for samples taken at room temperature indicate the presence of Fe2+ and Fe3+ mineral phases, which possibly correspond to ilmenite or magnetite. Finally, Sentinel-2A multi-spectral imager (MSI) data was used to map the distribution of iron oxides and study the influence of their distribution throughout the study area. A high correlation between Mössbauer spectroscopy and Sentinel-2A MSI data exists throughout the study area. The results suggest that farms close to the main Nevado del Ruíz Volcano have a more significant mineralogical variability. In contrast, more distant farms are characterized by soils with more iron oxides, the product of weathering, erosion, and human activities.
Highlights
Colombia's Coffee Axis, called in Spanish "Eje Cafetero" is a famous coffee region located near the intersection of four administrative regions: Caldas, Quindío, Risaralda, and Tolima, along the foothills of the Los Nevados National Park
The soils of the La Estrella farm (D3) are the most mineralogically diverse containing: feldspars such as sanidine, microcline and orthoclase, which indicate that the fertility of this soil is very high, because and together with the organic load, they favor the correct development of plants
From our remote sensing analysis with Sentinel-2A data, we observed a regional signal from bandwiths that indicate Hydroxyl bearing Iron and Ferrous oxides, which could explain the high acidity of soils, and this is consistent with our pH measurements (5.0 ± 0.5)
Summary
Colombia's Coffee Axis, called in Spanish "Eje Cafetero" is a famous coffee region located near the intersection of four administrative regions (departments): Caldas, Quindío, Risaralda, and Tolima, along the foothills of the Los Nevados National Park. The Coffee Axis is renowned for growing and producing most Colombian coffee, considered to be the best in the world. Farmers in the region apply different cropping practices (organic practices and traditional cultivation). This variety in cultivation techniques is thought to bring a unique characteristic to Colombian coffee. Different factors influence crop growth and yield (Reddy et al, 2003; Kang et al, 2009; Zhang et al, 2001). Inadequate nutrients result in low crop production, increased disease, and decreased plant resistance to pests. In these cases, soil intervention and the use of agrochemicals are necessary. Iron toxicity is a frequent problem in acid soils (Nenova, 2006)
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