Water stress integral as indicator of grape quality and yield parameters in a ‘Carménère’ vineyard with regulated deficit irrigation

Abstract

Water management and improving of water use efficiency (WUE) are very important issues on vineyards grown in semi-arid conditions. Stem water potential (Ψstem) is one of the most common tools to evaluate the water status in vineyards. However, some researchers have indicated that the water stress integral (SIΨ) could be a better parameter for explaining yield and quality long-term responses of vines to water deficit. Thus, the aim of this work was to study the performance of SIΨ as indicator of yield and quality parameter. In this regard, a completely randomized assay with four water application treatments (T0 = no water stress; T1 = mild water stress, T2 = moderate water stress and T3 = severe water stress) was weekly monitored from fruit set to harvest. SIΨ was calculated using the Ψstem measured at midday during 2011-2012 and 2012-2013 growing season. Yield (grape weight, grape diameter and number of grapes per cluster) and quality parameters (solids soluble °Brix (SS), total polyphenols index (TPI), and pH) were measured at harvest. Higher coefficient of determination were found between SIΨ and SS (r2=0.7). For other significant relationships, values of r2 fluctuated around 0.4. No significant relationships were found for yield parameters and pH (r2<0.3). Based on these results for both seasons, we concluded that SIΨ calculated from fruit set to harvest could be a good indicator of the soluble solids (°Brix) in vineyards 'Carmenere'.