Effect of irrigation and intra-vineyard soil variability on vegetative growth, yield and berry quality of 'Sangiovese' grapevines

Irrigation is becoming crucial for modern viticulture in Mediterranean regions where climate change is exacerbating the issue of water shortage. An experiment was conducted to evaluate the combined effect of irrigation and soil properties on vine water status, vegetative growth, fruit yield and berry quality. Three irrigation regimes were established in a commercial vineyard ('Sangiovese'): full irrigation (FI, 100% of crop evapotranspiration, ETc), sustained deficit irrigation (DI, 40% of FI), and rainfed (RF). To take into account the slight slope of the vineyard, three zones (A, B, C) were identified based on preliminary measurements of the stem water potential (SWP). Mapping of soil spatial variability was carried out using an electromagnetic induction sensor, which measured the soil apparent electrical conductivity (ECa) at three depths. The SWP was significantly different between irrigation treatments and the lowest values were measured in zone B, characterized by the lowest values of ECa. Significant differences in leaf area index (LAI) were found between irrigation treatments in zone A (0.74, 0.66, 0.51 in FI, DI and RF vines, respectively) and zone C (0.79, 0.60 and 0.52, respectively) but not in zone B (0.56, 0.57 and 0.55), where the lowest LAI values of FI and DI were measured but the maximum LAI of RF was recorded. The highest (3.10 kg) and lowest (1.25 kg) fruit yield vine-1 was measured in FI vines in zone A and DI vines in zone B, respectively. The berry anthocyanins and flavonols content at harvest was significantly lower in vines grown in the area with the lowest soil ECa where the differences between irrigation treatments were not significant. Our results highlight the importance of defining the spatial variability in the vineyard for precise irrigation management.