Correlations between canopy reflectance and leaf temperature in irrigated and droughted soybeans

Abstract

Effects of water stress on soybeans were characterized over a 4-day period in well-watered (WW) and water-stressed (WS) plots by measurements of leaf temperature, air temperature, and canopy reflectance. The objectives were to assess canopy reflectance as an indicator of drought stress in soybean and to determine if canopy reflectance could be predicted from leaf temperature. Reflectance from the WS plants was greater in the red portion of the visible spectrum and less at near-infrared wavelengths. Correlation coefficients with the reflectance measurements were generally greater with leaf temperature than with either the air temperature within the canopy or the differential between leaf and air temperatures. Coefficients of determination in excess of 0.8 could be obtained for models predicting either red or near-infrared reflectance as a function of leaf temperature by excluding those measurements taken shortly after irrigations. Plant size strongly affected model parameters.