The United States of America As Represented by the Secretary of

United States of America, As Represented by the Secretary of Agriculture

James R Mahan

John J Burke

Donald F Wanjura

Dan R Upchurch

The water-deficit stress of plants or crops is managed using plant temperatures to maximize product quality. The temperature of the target plant is repeatedly measured over a period of interest, and after each measurement, the plant temperature is compared with a predetermined plant setpoint temperature associated with a desired water-deficit stress level, above which temperature the plant is deemed to be in an undesired metabolic state. If the measured plant temperature is greater than the setpoint temperature, and humidity is not restrictive to plant cooling, then irrigation can be triggered to retain the plant within the desired stressed level, as determined by the temperature of the plant. By this method, irrigation can be withheld to increase plant temperature or applied to reduce plant temperature. The temperature of the plant is thus continuously increased and decreased relative to a desired temperature value that is indicative of a desired water-deficit stress.

Active management of plant canopy temperature as a tool for modifying plant metabolic activity

A process and device for managing irrigation of plants or crops using crop canopy temperate measurements by use of a specific time threshold. In this process, the canopy temperature of the target plant is repeatedly measured with an infrared thermometer. After each measurement, the canopy temperature is compared with a predetermined threshold canopy temperature, above which temperature the plant is thermally stressed. If the measured canopy temperature is less than or equal to the threshold canopy temperature, or if the existing humidity is restrictive to plant cooling, then irrigation is not indicated and the canopy temperature measurement is repeated at its designated time. However, if both the measured canopy temperature is greater than the threshold temperature, and the humidity is not restrictive to plant cooling, then an increment of time is added to a time register. The accumulated time in the time register is then compared to the time threshold, a predetermined constant defined as about the mean of the length of time per day that the canopy temperature for the plant, in a well-watered and non-stressed condition, exceeded the threshold canopy temperature in the target geographical area. As long as the accumulated time is substantially less than the time threshold, irrigation is either unnecessary or ineffective to achieve transpirational cooling, and the process is again repeated with measurement of the canopy temperature. However, once the accumulated time exceeds or is approximately equal to the time threshold, transpirational cooling is indicated and an irrigation signal is generated.

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Lubbock, TX, United States of America

James R Mahan