Design and validation of a soil moisture-based wireless sensors network for the smart irrigation of a pear orchard

In this work, we propose to transfer a soil moisture-based wireless sensor network (SM-WSN) to support the reduction of irrigation water consume in the Tuscany region (Italy). The SM-WSN was designed and validated in a commercial pear orchard during two growing seasons (2019-2020) in which the smart irrigation strategy was implemented and applied.

Initially, the micro irrigation system was assessed based on its performance in terms of water distribution uniformity (DU) evaluated with field measurements of emitter flow rates. Then, a zoning analysis was carried out to divide the orchard into homogeneous areas according to the normalized difference vegetation index (NDVI) detected with unmanned aerial vehicle (UAV) and GIS tools. These areas were used to define the topology of the SM-WSN and to investigate how water distribution uniformity can affect the vigour of the trees. A total of 6 “drill & drop” capacitance probes (Sentek Pty Ltd, Stepney, Australia) were installed in the field, after following a simplified laboratory calibration procedure. The hardware and the smartphone-based application, AgriNET, used to download from remote the sensors’ readings were provided by Tuctronics (Walla Walla, Washington, USA).

Assuming that the zoning outcome was only associated with the soil spatial variability, the effect of DU on the vigour of the trees has been identified. Moreover, unlike the ordinary irrigation scheduling applied in the farm, the smart system allowed maintaining the soil water content within a pre-defined optimal range, in which the upper and lower limits corresponded respectively to the soil field capacity and the threshold below which water stress occurs. Based on the smart irrigation management, a water-saving up to 50% of the total water supplied with ordinary scheduling was achieved during both the investigated growing seasons. Moreover, the quality of the productions (i.e °Brix, fruit size and firmness) were in line with the standard required by the farmer. The adoption of the new technology, aiming at identifying the most appropriate irrigation management, has the potential to generate positive economic returns and to reduce the environmental impacts.