Evaluating the performance of border irrigation through a glimpse at what happens in northern Italy

Abstract

<p>Achieving a good irrigation performance is not straightforward in border irrigation practices. This is almost always due to a lack of balance between natural factors (i.e. soil texture, infiltration characteristics), geometrical features (filed length, slope and border strip width) and management elements (flow rate and cut-off time). Such lack of balance makes it difficult to reach an optimal water depth across the field and a uniform intake opportunity time to satisfy crop water requirements at every point. In light of these concerns, studies investigating the current irrigation performance of border irrigated fields, and the potential improvements in irrigation managements are needed in order to better understand how we can keep this ancient but still crucial irrigation method alive.</p> <p>In this work, the results of an intensive monitoring campaign of more than ten border strip irrigation events carried out between the years 2021 and 2022 over two maize fields located in the Padana Plain (North Italy), are analyzed to understand the current performance level of this practice. Specifically, observed variables at the experimental sites included the actual flow rate, cut-off time and distance, advance and recession trajectories and water distribution uniformity, were investigated and their spatio-temporal variability discussed. Then, the IrriSurf2D model which is constituted by an integrated 2D hydrodynamic modelling framework intended to describe the dynamics of surface irrigation, was used for reproducing waterfront propagation under new irrigation management practices, i.e. different irrigation durations, flow rates and border layouts (slopes and border widths).</p> <p>Results show that microtopography, border width and antecedent moisture conditions before the irrigation intervention, plays a key role in the advancement of the waterfront along the longitudinal direction of the field and in the spatial variability of the water depth. A significant variability in time of advance and recession trajectories was observed over the experimental fields, whereas the distribution uniformity was generally consistent with literature standards. Additionally, the fields could be irrigated in considerably less time if the cut-off time is adjusted in according with the real flow rate and border layout. In general, the study has demonstrated a great potential to significantly improve irrigation performance by applying alternative field designs and operation strategies. These findings pave the way to define suitable guidelines for practical field irrigations with positive impacts in terms of water distribution uniformity and water saving. </p>