Ronit Yaa’ri

Cover crops (CCs) are widely used to improve soil function, support water regulation, and moderate vine vigor. This study evaluated alternative vineyard floor management strategies designed to improve ecosystem services while minimizing excessive competition with grapevines under semiarid Mediterranean conditions. A long-term, three-season field experiment was conducted in Bekoa, Israel, using four treatments: standard-management control, selective herbicide promoting annual winter grasses, interrow tall fescue (Festuca arundinacea-TF), and full-TF ground cover. Unlike conventional perennial CCs, the selective herbicide treatment promoted naturally occurring winter grass weeds that completed their life cycle before the dry summer period, thereby limiting prolonged competition with grapevines. Vine water status, vegetative-growth, yield components, and wine-color attributes were monitored. The tall fescue treatments progressively reduced vegetative growth and were associated with more negative stem water potential. Yield declined over the three growing seasons because cluster numbers decreased, with the largest cumulative decline in the tall fescue between-row treatment, followed by the full-cover tall fescue treatment. In contrast, the selective herbicide treatment consistently produced intermediate physiological and agronomic responses. In the third season, wines from the perennial turfgrass treatments exhibited greater color intensity, particularly under full-cover TF, while hue was not significantly affected. Overall, CC-based vineyard floor management affected vine performance and wine color attributes but the response depended on cover-type and duration of use. The selective promotion of naturally occurring winter grasses through targeted herbicide application produced intermediate responses in vine water status, vegetative growth, and yield, suggesting that limiting active ground cover to the wettest part of the season may reduce prolonged summer competition with grapevines.

Residual sugars (RS) in wine are the sugars that remain in a wine after fermentation is complete. In some wine styles, such as semi-dry wines, the accurate measurement of the RS concentration is critical for both qualitative and legislative reasons. Brix, measured by a simple refractometer, can give a good estimation of the RS concentration in the must, but during fermentation, the presence of alcohol leads to inaccurate sugar measurements. In order to measure the RS accurately, other more precise techniques are used, most of which are expensive or require professional skills. Therefore, novel approaches for rapid, easy, and practical measurements for estimating the sugar content have been suggested over the years. However, most of these methods do not supply an actual measurement of RS but rather give brix values, and those that measure RS involve special equipment, which is less relevant for small wineries. This study suggests a novel model for predicting and controlling the wine’s residual sugar. The data the model uses is the initial brix of the must before fermentation and its density during fermentation. The model was created by measuring actual residual sugars during the fermentation of natural and synthetic musts, with various degrees of initial brix levels, while simultaneously measuring their densities and correlating the two measurements. Linear regression between the residual sugar of the wine and its density was obtained for all treatments and repetitions (i.e., different values of must initial brix) with R² values above 0.97. Using the model, one can calculate (before commencing the fermentation) the density values at which the fermentation will reach a particular desired residual sugar value for a specific initial brix level; the model is applicable for the fermentation conditions used in this work, i.e., brix levels of 18–27 °Bx, Saccharomyces cerevisiae strains (fx-33 and fx-10) in common conditions of fermentation regarding temperature and aeration.

Residual sugars (RS) in wine are the sugars that remain in a wine after fermentation is complete. In some wine styles, such as semi-dry wines, the accurate measurement of the RS concentration is critical for both qualitative and legislative reasons. Brix, measured by a simple refractometer, can give a good estimation of the RS concentration in the must, but during fermentation, the presence of alcohol leads to inaccurate sugar measurements. In order to measure the RS accurately, other more precise techniques are used, most of which are expensive or require professional skills. Therefore, novel approaches for rapid, easy, and practical measurements for estimating the sugar content were suggested over the years. However, most of these methods do not supply an actual measurement of RS but rather give brix values, and those that measure RS involve special equipment, which is less relevant for small wineries. This study suggests a novel model for predicting and controlling the wine's residual sugar. The data the model uses is the initial brix of the must before fermentation and its density during fermentation. The model was created by measuring actual residual sugars during the fermentation of natural and synthetic musts, with various degrees of initial brix levels, while simultaneously measuring their densities and correlating the two measurements. Linear regression between the residual sugar of the wine and its density was obtained for all treatments and repetitions (i.e., different values of must initial brix) with R² values above 0.97. Using the model, one can calculate (before commencing the fermentation) the density values at which the fermentation will reach a particular desired residual sugar value for a specific initial brix level; the model is applicable for the fermentation conditions used in this work, i.e., brix levels of 18-27˚Bx, Saccharomyces cerevisiae strains (fx-33 and fx-10) in common conditions of fermentation regarding temperature and aeration.