Using LeafMon® to Study Water Stress Management in Avocados |
CWSI Overview |
The Cermetek LeafMon System provides the grower with a physical measurement of water stress in a plant. Crop Water Stress Index (CWSI) values range from 0.0 to 1.0. The higher the CWSI value, the greater the level of water stress present in the plant. See Figure 1. The avocado grower must establish a range of CWSI values that support good health in the Avocado trees. The LeafMon System measures water stress in the tree as the water level in the soil is manipulated. For the LeafMon to serve as a useful tool for the avocado grower, the grower must learn how his avocado trees react to changes in the CWSI. This is accomplished by exposing a monitored tree to both low and high levels of water stress. Observing and evaluating the tree’s response is critical to establishing a range of water stress levels that the avocado tree can safely endure. Once the Crop Water Stress Index range has been established, the CWSI value becomes a metric for the grower to manage irrigation timing, to increase water use efficiency and to improve crop sustainability. It has been Cermetek’s experience tht plants react to changes in water stress levels differently during the various phases of the plant’s growing cycle. For example, the level of water stress an avocado tree can accommodate during the fruit fall phase may cause damage to the crop during the flowering phase. It is important to continuously update the range of CWSI values throughout each phase of the growing cycle and to monitor the effects of water stress on the tree throughout each phase. The procedures described herein assume the use of only one crop water stress monitoring station. Employing additional monitoring stations increases the grower’s flexibility when dealing with weather and associated temperature/humidity variations encountered throughout the season and from season to season. This holds especially true for orchards with significant soil and terrain variations. Multiple CWSI monitoring stations allows for more precise tuning of the irrigation schedule to more accurately match the variations within the orchard. |
LeafMon Technology |
The Cermetek's LeafMon utilizes proven state-of-the-art non-contact, non-invasive, non-destructive sensor technology placed a safe distance from the leaf. Their presence causes no harm to the leaf and does not alter the plant’s function. The LeafMon Sensor Suite has been engineered to allow for easy upgrade of individual sensors should the sensor technology advance. LeafMon is fully inter-operable and will connect to most commercially available controllers equipped with a standard SDI-12, RS232 or RS485 interface. LeafMon measures the leaf temperature using non-contact IR sensors. Additionally, LeafMon employs unique sensors that monitor the following critical environmental conditions:
Dirt, moisture, wind, humidity, temperature and UV Radiation are not a threat to LeafMon's sensors or its performance. The LeafMon Sensor Suite never needs to be calibrated. The data from ALL sensors are used by LeafMon to calculate CWSI. |
AquaMon Technology |
Cermetek's AquaMon Remote Access Node is also fully inter-operable. Virtually any commercially available sensor can be connected to the AquaMon Controller. AquaMon will interface with standard SDI-12, RS232 and RS485 sensors as well as a maximum of 8 analog/digital I/O sensors. Additional daughter boards may be attached to the basic controller to provide additional sensor ports. The basic AquaMon Controller is supplied with an embedded GPRS RF cellular link providing Internet access. Remote AquaMon Nodes may also be connected via a 151MHz RF linked to a centrally located AquaMon Node operating as an Internet Hub. AquaMon may be powered by either an AC to DC converter (backup battery option recommended) or by a solar panel (backup battery required). An AquaMon Weather Station unit (utilizing the basic AquaMon Controller) is also available. |
System Requirements |
Each CWSI Monitoring System consists of one AquaMon Agriculture Remote Sensor Node and one LeafMon Sensor Suite. The following is supplied with each system:
RSVP is a web based product.
|
Installation |
Proper installation of the LeafMon Sensor Suite is essential to achieve actionable crop water stress values.
|
Learning Crop Tolerances of Water Stress |
Knowing how the crop reacts to various Crop Water Stress Index levels allows the grower to use CWSI as an irrigation tool. Learning what levels of CWSI are harmful to the tree or crop and what levels are beneficial allows the grower to utilize CWSI values to manage crop water stress through his irrigation practices. Keep in mind that the range of acceptable CWSI values corresponding to each plant stress category may vary throughout the growing cycle.
|
Crop Water Use Efficiency, Sustainability and Strategic Deficit Irrigation |
With the Low Water Stress CWSI (i.e., the lower CWSI limit) and the Excessive Water Stress CWSI (i.e., upper CWSI limit) values established for the crop, the grower has successfully determined the water stress limits required to safely maintain the tree within an acceptable range of water stress. Crop Water Use Efficiency is, essentially, the crop yield per amount of water applied to the crop. Knowing the maximum and minimum CWSI limits for the various phases of the crop growing cycle, the grower has the ability to place the tree into a “controlled” water stress condition during select phases of the crop growing cycle. This practice is generally referred to as Strategic Deficit Irrigation. By way of example, it is known that almond trees benefit from higher levels of water stress during hull-split as it prevents hull rot from damaging the crop. It is to be expected that there will be a tradeoff between controlled water stress and crop yield. Increasing water stress during some phases of the crop growing cycle will likely decrease crop yield. However, crop water stress can be managed to minimize crop yield loss while significantly reducing water usage. Using CWSI values to manage crops via a controlled water stress strategy, the grower can increase Water Use Efficiency and improve crop Sustainability. |
Conclusion |
When properly installed on a mature leaf in a tree representative of the orchard, the LeafMon System provides useful water stress management information to the grower. Establishing a “safe” range of CWSI values for a particular crop allows the grower the flexibility to manipulate irrigation parameters to control the level of water stress in the crop to attain a single specific goal, such as:
By monitoring CWSI values and observing overall tree health, the grower can determine when the avocado tree can be safely put into a more highly stressed condition thereby saving water and increasing crop water efficiency. This can be achieved without a significant impact on yield or adversely affecting long term tree health. |