Impact of Strip Subdivision on Water Conservation in Border Irrigation for Irregularly Shaped Fields

Border irrigation remains the most widely adopted surface irrigation method for row crops globally and is also extensively used in the Padana Plain (Italy), particularly for forage crops. In the Lombardy region, observations indicate that irrigation volumes can reach up to 3000 m³ /ha per event, often leading to excessive and inefficient water use. Given the ongoing decline in surface water availability, such practices are considered unsustainable in the long term. However, it is also unfeasible to replace them with more hard-path irrigation systems everywhere. In this context, a more realistic approach is to focus on optimizing irrigation scheduling and field layout, which can significantly reduce water consumption in gravity-fed surface irrigation. This study explores the water-saving potential of geometric reconfiguration in a 1.9-hectare, irregularly shaped, closed-end field in the Padana Plain, which is traditionally irrigated with an average volume of 2600 m³ /ha per irrigation event. High-resolution topographic data and the two-dimensional hydrodynamic model IrriSurf2D were used to simulate various land preparation scenarios, including strip subdivision and irrigation timing adjustments. Field implementation of the strip layout alone led to a 34 % reduction in water use, while model-based optimization of the irrigation durations suggested the potential for a total savings of up to 42 %. These findings demonstrate that precision surface irrigation strategies can significantly enhance the sustainability of border irrigation, even in complex field geometries, without abandoning traditional practices.