Espectroscopía de reflectancia: una herramienta para predecir las propiedades del suelo relacionadas con la clorosis férrica

Chlorosis due to iron (Fe) deficiency (internervial yellowing) is the most important nutritional problem a susceptible plant can have in calcareous soils. Fe chlorosis is related with calcium carbonate equivalent (CCE), clay content and Fe extracted with oxalate (Feo). Reflectance spectroscopy (RS) is a rapid, non-destructive, less expensive alternative tool that can be used to enhance or replace conventional methods of soil analysis. The aim of this work was to assess the usefulness of RS for the determination of some properties of Mediterranean soils including clay content, CCE, Feo, cation exchange capacity (CEC), organic matter (OM) and pH in water (pHw), with emphasis on those with a specially marked influence on the risk of Fe chlorosis. To this end, we used partial least-squares regression (PLS) to construct calibration models, leave-one-out cross-validation and an independent validation set. Our results testify to the usefulness of qualitative soil interpretations based on the variable importance for projection (VIP) as derived by PLS decomposition. The accuracy of predictions in each of the Vis-NIR, MIR and combined spectral regions differed considerably between properties. The R2adj and root mean square error (RMSE) for the external validation predictions were as follows: 0.83 and 37 mg kg-1 for clay content in the Vis-NIR-MIR range; 0.99 and 25 mg kg-1 for CCE, 0.80 and 0.1 mg kg-1 for Feo in the MIR range; 0.93 and 3 cmolc kg-1 for CEC in the Vis-NIR range; 0.87 and 2 mg kg-1 for OM in the Vis-NIR-MIR range, 0.61 and 0.2 for pHw in the MIR range. These results testify to the potential of RS in the Vis, NIR and MIR ranges for efficient soil analysis, the acquisition of soil information and the assessment of the risk of Fe chlorosis in soils.La clorosis debida a una deficiencia de hierro (Fe) (amarilleamiento internervial) es el problema nutricional más importante que una planta susceptible puede sufrir en suelos calcáreos. La clorosis férrica está relacionada con el contenido en carbonato cálcico equivalente (CCE), contenido de arcilla y Fe extraído con oxalato (Feo). La espectroscopía de reflectancia (RS) es una herramienta rápida, menos cara, no destructiva y proporciona una buena alternativa a los métodos convencionales de análisis. El objetivo de este trabajo fue estudiar la utilidad de la RS en la determinación de algunas propiedades (contenido de arcilla; CCE; Feo; capacidad de intercambio catiónico, CEC; materia orgánica, OM; y pHw) de los suelos de la región mediterránea, con énfasis en aquellas propiedades que más influyen en la clorosis férrica. Se utilizaron regresiones de mínimos cuadrados parciales (PLS), validación cruzada y validación externa para obtener los modelos de calibración. Nuestros resultados demuestran la validez en la interpretación cualitativa de los suelos de la variable de importancia para la proyección (VIP) descomponiendo los PLS. La precisión de las predicciones para cada región espectral Vis-NIR, MIR y combinaciones varió considerablemente entre las propiedades. Los valores de R2adj y RMSE obtenidos tras la validación externa fueron: contenido de arcilla=0,83 y 37 mg kg-1 para el intervalo Vis-NIR-MIR; CCE=0,99 y 25 mg kg-1, Feo=0,80 y 0,1 mg kg-1 para la región MIR; CEC=0,93 y 3 cmolc kg-1 para Vis-NIR; OM=0,87 y 2 mg kg-1 para el intervalo Vis-NIR-MIR; y pHw =0,61 y 0,2 para la región MIR, respectivamente. Este trabajo demostró el potencial de la RS usando las regiones del Vis, NIR y MIR para un análisis eficiente de las propiedades, adquirir información y detectar el riesgo de clorosis férrica en los suelos

Reflectance spectroscopy: a tool for predicting soil properties related to the incidence of Fe chlorosis

Chlorosis due to iron (Fe) deficiency (internervial yellowing) is the most important nutritional problem a susceptible plant can have in calcareous soils. Fe chlorosis is related with calcium carbonate equivalent (CCE), clay content and Fe extracted with oxalate (Feo). Reflectance spectroscopy (RS) is a rapid, non-destructive, less expensive alternative tool that can be used to enhance or replace conventional methods of soil analysis. The aim of this work was to assess the usefulness of RS for the determination of some properties of Mediterranean soils including clay content, CCE, Feo, cation exchange capacity (CEC), organic matter (OM) and pH in water (pHw), with emphasis on those with a specially marked influence on the risk of Fe chlorosis. To this end, we used partial least-squares regression (PLS) to construct calibration models, leave-one-out cross-validation and an independent validation set. Our results testify to the usefulness of qualitative soil interpretations based on the variable importance for projection (VIP) as derived by PLS decomposition. The accuracy of predictions in each of the Vis-NIR, MIR and combined spectral regions differed considerably between properties. The R2adj and root mean square error (RMSE) for the external validation predictions were as follows: 0.83 and 37 mg kg-1 for clay content in the Vis-NIR-MIR range; 0.99 and 25 mg kg-1 for CCE, 0.80 and 0.1 mg kg-1 for Feo in the MIR range; 0.93 and 3 cmolc kg-1 for CEC in the Vis-NIR range; 0.87 and 2 mg kg-1 for OM in the Vis-NIR-MIR range, 0.61 and 0.2 for pHw in the MIR range. These results testify to the potential of RS in the Vis, NIR and MIR ranges for efficient soil analysis, the acquisition of soil information and the assessment of the risk of Fe chlorosis in soils