Spectral properties of leaves deficient in iron, sulfur, magnesium, and manganese

In crop plants, deficiency of an essential element may drastically reduce growth rate and yield. Research on the use of leaf spectral properties in the detection of crop mineral deficiency is needed. The objective of this study was to examine the effects of Fe, S, Mg, and Mn deficiency on reflectance (R), absorptance (A), and transmittance (T) spectra of barley (Hordeum vulgare L.), wheat (Triticum aestivum L.), corn (Zea mays L.), and sunflower (Helianthus annuus L.) leaves. Plants were grown in the greenhouse in nutrient solution. Chlorophyll (Chl), Fe, S, Mg, and Mn concentrations and spectral properties were determined on the youngest fully expanded leaf when deficiency symptoms were clearly manifested. In all species, mineral deficiency affected leaf concentration of the deficient element and also of other elements. Nutrient deficiency reduced Chl concentration and A, and increased R and T. Iron deficiency severely affected all species, and corn was the species most sensitive to all deficiencies. Reflectance, A, and T spectra of leaves were correlated with leaf Chl concentration. Our results suggested that all nutritional deficiencies reduce leaf Chl concentration, and subsequently this reduction increases leaf R and T, decreases leaf A, and shortens the red-edge position, defined as the inflection point that occurs in the rapid transition between red and near-infrared. Modifications in leaf spectral properties were not characteristic of nutrient deficiency, but were always observed in the same wavelengths.