Agronomic and must quality performance of <i>Vitis vinifera</i> L. <i>cv.</i> ‘Loureiro’: a four-year study

In the Vinho Verde region, one of the most widely cultivated grapevine varieties is Vitis vinifera L. cv. ‘Loureiro’, which is produced under a rainfed conditions. However, irrigation is increasing being implemented to mitigate the effects of climate change. In this sense, the present study evaluated three different irrigation management strategies - rainfed (R), deficit irrigation (DI) and irrigation (I) - during four growing seasons, between 2019 and 2022. The main goal was to assess the influence of irrigation strategies on agronomic productivity and must quality. In order to achieve this objective, a set of parameters related to vine yield and must quality was assessed. In addition, the stem water potential (SWP) was measured, and vineyard transpiration and actual evapotranspiration were estimated. The results showed clear seasonality in production, with higher productivity followed by a decline, ranging from 19 766.5 kg/ha in R 2020 to 4 726.1 kg/h in I 2021.The study demonstrated that irrigation has a favourable long-term effect on yield. This phenomenon can be ascribed to the observation that, although only numerical disparities between treatments were detected in the initial years, significant variations (p&lt;0.05) were identified in 2022, between irrigation treatments. Furthermore, the DI strategy exhibited optimal water productivity, indicating high water use efficiency across the entire studied period. These findings suggest that maintenance irrigation, even in cases where it is found to be deficient, can result in enhanced water productivity in the short term, and higher productivity rates in the long-term.