Remotely Measuring Chlorophyll Content in Corn Leaves with Differing Nitrogen Levels and Relative Water Content

Measuring a cropʹs physiological parameters provides information for interpreting its response to the environment. Remote sensing is quickly becoming recognized as a valuable tool that has the potential to assess a wide variety of physiological properties over a large area in a short amount of time. This study examined the relationship of corn (Zea mays L.) leaf spectral response to its chlorophyll content and relative water content. The effects of N stress and water stress were examined on each of these physiological parameters. Over the years, several spectral indices have been introduced for a wide variety of applications. A number of these indices were evaluated for their ability to predict the parameters in question. The normalized difference between the first derivatives at 525 and 570 nm, as well as the wavelength location of the red edge, showed a strong association with chlorophyll content (r2 = 0.81 and 0.80, respectively). Even stronger relationships to chlorophyll content were observed with the ratios of 600/680 nm (r2 = 0.83) and 630/680 nm (r2 = 0.83). Thus, our results suggest that spectral reflectance measurements hold promise for the assessment of some physiological parameters at the leaf level. Further investigation is needed to evaluate the effectiveness of such techniques at the canopy level.