Nature is in effect a real time sensor with constant flux changes from various inputs. Trees do this by regulating the amount of water that moves from the soil solution into the roots, up through the xylem, and out to the atmosphere by opening or closing of stomatal pores. This cannot be achieved without the energy from the sun which is driving photosynthesis. With this relationship the cumulative use of water over a season and the resulting photosynthetic activity provides the plant sugars that move through the tree increasing total dry matter and or yield.
Although should the nutrients not be available in the soil solution, which is dependent on soil moisture, then yields can be reduced. If the paddocks are being over irrigated leaching can occur removing fertiliser from the rootzone resulting in reduced efficiency. Soil moisture sensors placed at a 15, 30 and 90cm intervals, common soil profile measurements, to monitor where the moisture levels are can help prevent deep drainage losses, and over or under irrigating which could lead to ineffective energy use. The recent energy audits have included soil sensors as part of the energy water nexus with some sites witnessing a reduction of up to 30% in water use.
Soil moisture sensors alone are not without issues. The contact with the soil is in comparison a very small sample of what may be occurring across a larger area (hectares) which can have varying soil properties (spatial variability). Further, it can get complex when two trees of the same species are close to one another, as they undertake Hydraulic Coupling, transferring water and nutrient through the root systems and between them.
Typically, pump and flow meter data is used to estimate the volume of water applied from an irrigation event. To improve the efficiency in tree crops it is becoming increasingly common to measure the volume of water moving through tree stems using sap flow meters. Water stress can also be measured using stem psychrometers. This allows growers to see when their trees are active (day or night), and to closely match the total applied irrigation water to tree water use at exactly the right time.
To achieve greater efficiencies, increase production while minimising resource use such as energy and water a suite of available sensors are available, these include;
Along with the mentioned sensors there are many more which cover many other factors. Dam and tank water levels can also be monitored along with the ability to auto start pumps according to rules set by the software that displays the incoming data. Armed with this data improvements in efficiency can be made.