A novel methodology for irrigation scheduling using plant-based measurements and mathematical modelling

Because water is a scarce resource with often intense competition between different users, the search for an optimal irrigation strategy remains an important research objective. In the present study, a new methodology for irrigation scheduling is developed. The methodology combines the use of biosensors for monitoring plant responses with a mathematical model. The model incorporates a mechanistic description of the dynamic water transport in plants and it allows distinction between radial stem growth and the water-related shrinkage and swelling of the stem. Continuously measured stem sap flow rates are used as input for the model, while model calibration is performed using stem diameter variation data measured with a linear variable displacement transducer. The calibrated model is also able to simulate the stem water potential which is continuously compared to a critical threshold value for determination of the exact timing of the irrigation. The quantity of water to be supplied is obtained by integrating the measured sap flow pattern over time. For this novel methodology to be useful in practice, software was developed as well. This software not only enables the acquisition of the data and real-time visualisation of the plant health status, but also allows real-time simulation and calibration of the mathematical model and, finally, the irrigation scheduling itself. The new methodology allows true plant-dependent irrigation control by predicting the optimal timing for irrigation and the exact amount of water required by the plant.