Apparatus for determining water stress in crops

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. When data for a different crop are needed, the memory may be removed and replaced by a memory containing the appropriate crop data, or, if erasable, the memory may be erased and reprogrammed for the different crop. The apparatus preferably includes a memory for storing a number of calculated crop water stress indices, each calculated from conditions sensed on a different day, in records including the date of the measurements. The stored indices can be retrieved and displayed with their measurement dates so that historical trends of crop water stress may be discerned.