Abstract

Studies have shown that measurement of plant water status (PWS) provides the key information necessary to implement efficient irrigation management scheme in orchard and vineyard crops. A pressure chamber is often used to measure PWS. However, this technique is labor intensive, tedious and time-consuming. To address these issues,we developed a sensor suite consisting of a thermal infrared (rR) sensor and relevant environmental parameters (ambient temperature, photosynthetically active radiation (PAR), wind speed and relative humidity) and tested it extensively in almond, walnut, and grape crops. The system was found to work well in all three crops. However, this sensor suite was quite bulky and we noticed temporal drifts in the calibration curve as the season progressed. To address these issues, we developed a continuous leaf monitoring system that included same sensors as the sensor suite. We have deployed 22 such leaf monitors in almond and walnut orchards in Nickels Soil Laboratory, Arbuckle, CA, USA and interfaced them to a wireless mesh network so that data could be uploaded to the internet through a gateway computer and accessedthrough the web. The system also included a controller capable of actuating latching solenoid valves to manage precision irrigation in the orchard. Field data collected from these experiments were used to calculate daily crop water stress index (CWSI). The results showed that this system has the potential to be used as irrigation management tool as it was able to provide daily CWSIvalues which followed similar pattern as the actual PWSvalues. Key words: Leaf temperature, crop water stress index, cwsi, irrigation scheduling, continuous measurement, wireless mesh network, plant water status, almonds, walnuts, grapes