Canopy temperature as a crop water stress indicator

Canopy temperatures, obtained by infrared thermometry, along with wet- and dry-bulb air temperatures and an estimate of net radiation were used in equations derived from energy balance considerations to calculate a crop water stress index (CWSI). Theoretical limits were developed for the canopy air temperature difference as related to the air vapor pressure deficit. The CWSI was shown to be equal to 1 - E/Ep, the ratio of actual to potential evapotranspiration obtained from the Penman-Monteith equation. Four experimental plots, planted to wheat, received postemergence irrigations at different times to create different degrees of water stress. Pertinent variables were measured between 1340 and 1400 each day (except some weekends). The CWSI, plotted as a function of time, closely paralleled a plot of the extractable soil water in the 0- to 1.1-m zone. The usefulness and limitations of the index are discussed.

[1]  J. Monteith,et al.  Radiative temperature in the heat balance of natural surfaces , 1962 .

[2]  C. B. Tanner.  Plant Temperatures 1 , 1963 .

[3]  D. M. Gates,et al.  Leaf Temperature and Transpiration1 , 1964 .

[4]  C. Wiegand,et al.  Influences of Plant Moisture Stress, Solar Radiation, and Air Temperature on Cotton Leaf Temperature1 , 1966 .

[5]  C. H. M. van Bavel,et al.  Changes in canopy resistance to water loss from alfalfa induced by soil water depletion , 1967 .

[6]  Leo J. Fritschen,et al.  Net and solar radiation relations over irrigated field crops , 1967 .

[7]  C. H. M. van Bavel,et al.  Water Loss from a Sorghum Field and Stomatal Control1 , 1968 .

[8]  I. F. Long,et al.  Surface Resistance of Crop Canopies , 1969 .

[9]  Ray D. Jackson,et al.  A Method for Determination of Infrared Emittance of Leaves , 1969 .

[10]  D. L. Nofziger,et al.  Experimental Curves and Rates of Change from Piecewise Parabolic Fits1 , 1972 .

[11]  W. Ehrler.  Cotton Leaf Temperatures as Related to Soil Water Depletion and Meteorological Factors1 , 1973 .

[12]  S. Idso,et al.  Estimating soil moisture in the root zone of crops: A technique adaptable to remote sensing , 1976 .

[13]  H. R. Oliver,et al.  On Penman's equation for estimating regional evaporation , 1977 .

[14]  S. Idso,et al.  Wheat canopy temperature: A practical tool for evaluating water requirements , 1977 .

[15]  S. Idso,et al.  Remote-Sensing of Crop Yields , 1977, Science.

[16]  G. Russell.  Crop evaporation, surface resistance and soil water status. , 1980 .

[17]  S. Idso,et al.  Normalizing the stress-degree-day parameter for environmental variability☆ , 1981 .

[18]  S. Idso,et al.  Determining Soil‐Induced Plant Water Potential Depressions in Alfalfa by Means of Infrared Thermometry1 , 1981 .

[19]  Ray D. Jackson,et al.  Soil Moisture Inferences from Thermal-Infrared Measurements of Vegetation Temperatures , 1982, IEEE Transactions on Geoscience and Remote Sensing.