Spectra of Normal and Nutrient-Deficient Maize Leaves
1974
Al-Abbas, A. H. | Barr, R. | Hall, J. D. | Crane, F. L. | Baumgardner, M. F.
Since the advent of spectral mapping and identification of vegetation by remote sensing methods, information about differences in plant nutrient status has gained prominence. Therefore, we decided to study the reflectance, transmittance, and absorptance spectra of “normal” and six types of nutrient-deficient maize (Zea mays L.) leaves. Nitrogen-, phosphorus-, potassium-, sulfur-, magnesium-, and calcium-deficient leaves were analyzed at 30 selected wavelengths from 500 to 2,600 nm. The analysis of variance showed significant differences in reflectance, transmittance, and absorptance in the visible wavelengths among leaves 3, 4, and 5, among the 7 treatments, and among the interactions of leaf positions and treatments. Only treatments in the infrared wavelengths produced significant differences. The chlorophyll concentration of leaves in all nutrient-deficiency treatments was lower than that of leaves in the control. Percent moisture in the S-, Mg- and N-deficiencies was higher. Positive correlations were obtained (r = 0.7) between moisture content and percent absorptance at both 1,450 and 1,930 nm. Second degree polynomial regression analysis of leaf thickness and leaf moisture content showed that these two variables were significantly and directly related (R = 0.894). Leaves from the P- and Ca-deficient plants absorbed less energy than those from normal plants in the near infrared wavelengths; leaves from the S-, Mg-, K-, and N-deficient plants absorbed more than the normal. Leaf thermograms were prepared on normal and S-and N-deficient leaves. Both S- and N-deficient leaves had higher temperatures than normal leaves.
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