Advances in technology mean that sensors that were once the realm of research scientists are now readily available for on-farm use.




 The Implex SapLinx sensor is an Australian designed and manufactured sap flow sensor which uses the heat pulse technique.




Sap Flow sensors becoming more popular as an irrigation management tool and can be used in place of or alongside the more traditional profiling capacitance probes. The SapLinx probe has a set of 3 pins which are inserted into the trunk of the tree. The pins are inserted into stainless steel sleeves, to make removal easier.
The lower pin acts as a reference sensor, measuring the temperature of the sap in the xylem, via a pair of thermistors. The centre pin is fitted with heating elements. The top pin measures the temperature of the sap after the heater. A pulse of electricity is applied to the heating element and the probe makes some calculations based on the difference in temperature between the inner and outer sensors on the top and bottom pins.
The sensor has an SDI-12 interface so is compatible with a wide range of telemetry equipment and loggers. The sensors draw around 270 mA of current during the read cycle, which takes around 90 sec to complete.




 The size of the trunk of a tree increases and decreases with daily transpiration. The DE1T dendrometer consists of a spring loaded piston, the position of which is measured using a highly accurate displacement sensor.




Changes in the dendrometer readings can be used to determine the Daily Growth (the increase in maximum value from one day to the next) and the maximum daily shrinkage (the difference between the maximum and minimum value for the time period). In irrigation management, it is this second parameter which is the most important, as the maximum daily shrinkage (MDS) will be higher when plants are well irrigated than when they are stressed. The trunk dendrometers have an SDI-12 interface.




 Fruit size sensors are used to track the growth of various types of fruit.




The FI-MT sensors have a pair of lightweight arms which sit on either side of the fruit. The position of the arms is measured using a precision displacement sensor. The change in position can be tracked from one day to the next and used to track daily growth. The Fruit size sensors have an SDI-12 interface.




Soil oxygen sensors do just what the name suggests, measuring the level of oxygen in the soil.




When soil is saturated, all of the oxygen is displaced from the soil. Plant roots will shut down, putting an end to growth. The MIJ-03  sensors have a measurement range of between 0 and 20.9 (which is the oxygen level in the air).  The sensors provide a milli-volt output and do not require a power source.




Just as you can measure sap flow to infer the soil water status of a plant, you can also measure water tension in the tree’s woody tissue. FloraPulse’s micro-tensiometer is designed for just that purpose.




The FloraPulse sensor is built around a micro-chip tension sensor. It is embedded in to the trunk of the tree, using a hole which is drilled in to the trunk. The hole depth is chosen to ensure the probe tip is in the xylem of the tree. The probes are supplied with an SDI-12 converter, giving them an SDI-12 output for easy connection to a wide range of telemetry and loggers.




More information is available on the FloraPulse probe and Installation brochures.