Reliability of capacitance type soil moisture sensors for their use in automated scheduling of drip irrigation in orchards

Drip irrigation applies water to the soil in an efficient way, reducing the wet surface and supplying water close to the root zone. However, it determines a heterogeneous distribution of water in the soil that complicates its monitoring with sensors. To this end, the purpose of this work was to characterize and understand the main sources of variability involved in the measurement with capacitance sensors in an apple orchard (Malus domestica 'Golden Reinders'). The results showed that (1) the main source of variability was the position and extension of wet bulbs, (2) thanks to Hydrus model, we could understand the uncertainty in soil water dynamics and (3) despite the variability, it was possible to automate the irrigation in an apple orchard and give to each plot the water doses that needed.