Every drop counts: optimizing water use efficiency for sustainable tomato production

Ensuring food production in the face of increasing water scarcity is one of the main challenges for sustainable agriculture worldwide. As climate change intensifies and water availability becomes increasingly limited, the adoption of strategies that enhance water use efficiency in agriculture is imperative. The objective of this study was to evaluate whether the combination of deficit irrigation and biostimulant application can maintain tomato yield while improving water and energy use efficiency, thereby contributing to more sustainable horticultural production systems. The study evaluated five irrigation replacement levels, 40, 60, 80, 100, and 120% of crop evapotranspiration (ETc) with or without the application of a biostimulant derived from Ascophyllum nodosum extract (ANE), under protected cultivation over two production cycles. As tomato plants were subjected to increasing levels of water deficit, the negative impacts on crop performance became more pronounced. However, when comparing the same irrigation replacement levels, the ANE applications proved beneficial by mitigating the water stress effects on the crop. The study demonstrated that moderate deficit irrigation (80% ETc) combined with ANE promoted stability across both production cycles, sustaining yields comparable to full irrigation (100% ETc without ANE) while reducing water use by 20%. Plants under 80% + ANE enhanced photosynthetic rates by up to 5.7–7.8% and kept leaf relative water content and temperature close to unstressed plants. This strategy also achieved favorable energy productivity, ranging from 0.70 to 0.72 kg MJ − 1 . Conversely, overirrigation (120% ETc) added an unnecessary energy cost of 0.6 MJ plant − 1 and decreased water use efficiency by up to 15.7–16.9%, triggering a diminishing returns effect. The integrated management strategy of applying 80% ETc + ANE proved to be an environmentally responsible solution for water saving in horticulture, contributing to more resource-efficient food systems through improved water management in tomato production.