Abstract: An apparatus for determining the water stress condition of an agricultural crop growing in a field includes sensors for sensing environmental and crop conditions, such as air temperature, crop canopy temperature and relative humidity, and for generating signals indicative of the sensed conditions, a microprocessor for receiving the generated signals and for calculating a crop water stress index from the signals and a visual display for displaying, in the field, the calculated index. In one embodiment, the sensors are mounted in a pistollike, hand held housing and the microprocessor, display and a keyboard control are carried by a second housing. The microprocessor compares one or more of the sensed conditions to reasonable value limits and rejects a set of measurements containing values beyond the limits. Crop-specific data needed to calculate water stress indices for a particular crop are stored in a programmable, read only memory.

Abstract: An apparatus and method for indicating whether irrigation of an agricultural crop is required based on the measurement of crop water stress. The apparatus and method include a plurality of sensors for sensing a plurality of conditions related to the agricultural area, including crop canopy and air temperatures, and relative humidity, from which the water stress condition of the crop can be determined, and for generating signals representative of each of the sensed parameters; an electronic device connected to the sensors receiving the sensor signals for determining therefrom the water stress condition of the crop; and an output device connected to the electronic device for visually displaying the calculated water stress index. The apparatus may be embodied in a portable unit that provides immediate analysis of environmental and crop data along with the crop water stress index.