Agro-hydrological sensor and model-based tools for sustainable irrigation management of sparse crops under soil water deficit conditions

This thesis proposes new perspectives on water management in sparse crop systems by implementing the feed-forward (FFC) and feedback (FBC) control irrigation scheduling approaches. The main research line implements the FBC irrigation management approach, according to a technology transfer activity, founded by the Tuscany region. Specifically, the research focuses on designing and validating a soil moisture-based wireless sensors network for smart irrigation in a pear orchard. This technology transfer activity made it possible to save a considerable amount of water (up to 50%) in comparison with conventional irrigation management, allowing a substantial reduction of the irrigation duration from 6-7 (ordinary management) to 2-3 hours. At the agronomic level, a maintenance of the production was observed, compared with the average of the last four years. In line with the main research line, the thesis moved to evaluate the performance of the FAO 56 dual Kc approach to monitor the soil plant water status of a traditional irrigated cherry orchard (Prunus avium, Bing) in California. The model was calibrated by comparison with actual evapotranspiration data measured through an eddy covariance tower. The results confirm the suitability of the FAO 56 Dual Kc approach to assess both soil evaporation and crop transpiration, thus providing a better understanding of the dynamics of actual cherry water consumption. The last research has led to deepening the understanding of the spatial variability of the soil’s physical properties, using the proximity EM38 sensor to detect quick and reliable proxy variable: the so-called soil electrical conductivity. To address these issues, the study led to the product improvement, specifically making the EM38 sensor easier to use, adaptable, using it with cost-effective open-source DAQ. The low-cost DAQ it is based on Raspberry Pi and allows to collect of speed and positioning of the EM-38 (Geonics Inc.) output. Preliminary results provided evidence of the possibility of extracting the analogical signal from the device, which is strongly responsive to the soil’s physical properties variation. Additionally, the proposed DAQ system has proved to accurately estimate the spatial patterns of the investigated soil physical properties. All the topics discussed through this thesis, aimed to contribute to the know- how in the field of precision irrigation. Specifically, to introduce the FFC and FBC protocols as accurate approaches that can impact on the water use efficiency WUE of the agricultural production system.