Precision irrigation in Almonds based on plant water status

Abstract

The irrigation can to increase the yield agricultural crops. The conventional method to determinate the quantity and depth water available uses moisture sensors that considers, basically, the soil features. The objective of this study was evaluate the irrigate in almonds orchard, based on real-time plant water status as estimated by a wireless network of these continuous leaf monitors, comparing with results obtained by grower practice, using soil moisture sensors. The irrigation system that used management in real-time resulted in reduction around 70% of the water applied compared to ET, and 85% of water applied compared to grower practice which used soil moisture sensors. Precision irrigation or variable rate irrigation has the potential to conserve water by increasing water use efficiency and water productivity. For orchard and vineyard crops, which have extensive root systems, soil moisture content measured at shallow depths may not adequately represent total water available to the plants. Plant water status is believed to be a good indicator of irrigation needs of trees and vines (Dhillon et al., 2014). A pressure chamber is often used to measure plant water status. While this device is considered as the standard to measure plant water status, it is time consuming and tedious to use and measurements must be done around solar noon, when California's Central valley temperature can exceed about 38° C. Udompetaikul (2012) and Dhillon et al. (2014) developed a sensor suite to measure plant water status using a suite of sensors that included a thermal IR sensor to measure leaf temperature, and sensors to measure air temperature, relative humidity, incident radiation, and wind speed. They conducted extensive field tests in almond, walnut and grape crops and showed that this sensor suite can successfully predict plant water status. Dhillon (2015) and Dhillon et al. (2017) further developed this system to continuously monitor plant water status and interfaced it to a wireless mesh network so that data can be uploaded to the web and made available on a personal computer or a handheld device. This version of the sensor was called a continuous leaf monitor. This system could not only monitor the system, but also could control latching solenoid valves through the same wireless mesh network to implement precision irrigation. The objective of this study was to irrigate orchard crops based on real-time plant water status as estimated by a wireless network of these continuous leaf monitors. To accomplish this objective, two management zones were created based on spatial variability in soil (texture, electrical conductivity (EC) at two different depths, and digital elevation) and plant (light interception and canopy temperature) characteristics