There is growing interest in employing hand-held radiometry as a nondestructive research tool in lieu of or support of more tedious vegetation measurements. The objective of this study was to evaluate such techniques on corn. The spectral radiances from corn plots 1.8 m in diameter were measured using a three-band radiometer elevated 3.7 m above the ground. The three spectral bands used corresponded to NASA'S Landsat-D Thematic Mapper bands TM3 (0.63–0.69 μm), TM4 (0.76–0.90 μm), and TM5 (1.55–1.75 μm). Periodically throughout the growing season a plot was selected and radiometrically measured then harvested for measurement of several agronomic variables. By the end of the growing season, a total of 43 plots had been measured with solar zenith angles ranging between 16 and 44°. Significant relationships were found between various combinations of the radiance data and the wet and dry total biomass, plant height, fraction of ground covered by plants, wet and dry green leaf biomass, green leaf area index, fraction of leaf chlorosis, and total plant water content. Some of these relationships were found to be redundant since several of the agronomic variables were highly correlated to one another. In addition, the TM5 band did not provide any marked improvement in the relationships to the agronomic variables. The relationships between the radiance data and agronomic variables represent a nondestructive remote sensing technique for researching the growth of corn canopies.
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