Evaluation of Cotton Canopy Temperature to Detect Crop Water Stress

ABSTRACT CANOPY temperature of cotton was shown to be useful as an indicator of crop water stress resulting from both soil water deficit (matric) and soil water salinity (osmotic) stresses. The relationship between canopy-air temperature difference and ambient vapor pressure deficit was shown not to depend on cotton row spacing, not to exhibit seasonal trends and to be applicable to a wide cotton production region. Cotton lint yields from two experiments were found to be negatively correlated to the mean seasonal crop water stress index. The crop water stress index was found to be sensitive to crop osmotic stress resulting from high soil water salinity when the soil water matric potential was negligible. Canopy and air temperature difference, in conjunction with ambient vapor pressure measurements, formulated into the crop water stress index appears to be useful in quantifying crop water stress from both soil water deficits and soil salinity. Therefore the crop water stress index appears useful for indicating the need for irrigating cotton.

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