Assessing the water conservation potential of optimized surface irrigation management in Northern Italy

The effects of climate change on water availability affect the performance of surface irrigation, which is the oldest and most common method of water application to row crops worldwide. A paradigm shift towards strategies aimed at increasing flex- ibility of irrigation scheduling and improving the design and management of field layouts and irrigation practices should be explored to promote water conservation at the farm scale. In this study, we investigate how by adopting a more flexible irrigation scheduling and optimizing irrigation management variables and field layout it is possible to increase the efficiency of border irrigation and thus achieve water conservations and improve quality of crop production. The analysis of the actual performance of border irrigation was carried out on two maize fields located in the Padana Plain (Northern Italy) in 2 years characterized by different rainfall patterns (i.e. 2021 and 2022). Based on this information, continuous monitoring of soil moisture status combined with the AquaCrop-OS agro-hydrological model was used to manage flexible irrigation scheduling over the experimental fields, while the optimization of irrigation management (flowrate per unit width and cutoff time) and field geometries (border width and slope) was studied using WinSRFR 5.1 USDA software, which was properly calibrated by measures of waterfront advance and recession. The results show that with flexible irrigation scheduling and proper irriga- tion management and field layout, significant water conservation can be achieved. Specifically, in the case study, seasonal water conservation of about 10% was obtained just by scheduling irrigation based on actual crop water needs in a very dry agricultural season, while water conservation reached up to 60% in a wetter season. On average, an additional 7% of water conservation was achieved over the agricultural season when the irrigation duration was correctly applied to each border of the experimental plots, while approximately 20% of water was conserved when the border width was correctly designed based on inflow availability. These results provide useful information for improving the management of border irrigation in practice, both under current conditions and in prospective of increasing freshwater scarcity in the future.