A novel variable-rate drip irrigation system to improve water use of vegetable crops in semiarid conditions

Irrigation system design and management focus on achieving the highest uniformity across plots. However, plots are not homogeneous and therefore require different irrigation depths in different areas. In this context, variable-rate irrigation systems have emerged as a solution that allows irrigation doses to be adjusted according to intra-plot heterogeneity. This study aimed to develop a commercially viable variable-rate drip irrigation (VRDI) system. The system delivers differentiated application rates across normalised difference vegetation index (NDVI) derived site-specific management zones (SSMZs), while maintaining a single control unit per irrigation sector. Unlike previous VRDI implementations often reported in vineyards and relying on bespoke emitters or complex zoning and control, the proposed design uses standard, commercially available self-compensating driplines with different nominal flow rates, reducing cost and operational complexity. This study was conducted on a 1.65-ha commercial plot of broccoli (Brassica oleracea L. var. italica). A methodology was developed that covered everything from the identification of management zones to the installation of the VRDI system. Two areas with different productive potentials were determined; in the area with the highest potential, 1.6 L/h emitters were used, whereas in the one with the lowest potential, 2.0 L/h emitters were used to increase yield. Results indicate a reduction in the yield gap between zones. In the least productive area fitted with 2.0 L/h emitters, significant differences were observed compared with its control zone. In this area, an increase in yield and water productivity (WP) of 44.1 % and 16.2 %, respectively, was achieved. In conclusion, this VRDI system provides a simple, practical and commercially applicable solution for optimising water use in agriculture, with potential scalability to other crops and regions as a cost-effective tool for farmers and other stakeholders.