Technical Yearbook 2023

JANUARY/FEBRUARY

Management of vine water stress through foliar treatment with microbial derivatives* By Lucia Giordano, Tommaso Frioni & Fabrizio Battista

An innovative microbial derivative has been developed to protect vines from the negative effects of water stress. The application of this product has been the subject of an in-depth study showing that the treatment enables faster and more effective osmotic regulation, limiting production and quality losses in increasingly frequent water stress situations. Vineyard water levels are a key aspect to be managed during the season to ensure a good vegetative-production balance and optimal production results. Against the backdrop of global warming, dry winters are rising, with a poor accumulation of soil water reserves. Spring and summer are characterised by frequent extreme events or intense rain events that bring no benefits to water balance in the vineyard.

moment for water shortage is between fruit set and veraison, during the grape’s vegetative growth phase. Water stress occurring when cell division and development processes are active impacts final yield much more than stresses of the same intensity occurring at veraison or post-veraison. Furthermore, loss of product caused by premature stress is irreversible, even if the amount of water replenished during the rest of the season increases. If water deficit is moderate and controlled in the final phase of ripening, it could also have positive effects on quality, especially for red grapes, whereas the first reaction of the plant to a substantial deficit is a slowdown in photosynthetic activity. When stress lasts several days, the stomata close and photosynthesis ceases, increasing leaf temperature as there is no transpiration thermoregulation. If these conditions continue for long periods, cell turgor is lost, with the accumulation of reactive oxidising species (mainly hydrogen peroxide) in the tissues, which is the cause of classic leaf yellowing and necrosis that can cause permanent damage to the photosynthesis system.

It is estimated that 99% of the water used by vines is transpired to allow photochemical and thermoregulation tissue processes. “Constitutional water”, namely water stored in the plant which is essential for maintaining the right cell turgor, is necessary for growth, stomata movement and root system functioning. With the same amount of rainfall, high temperatures increase vineyard evapotranspiration, and the incidence of water stress rises even in the wettest districts. The amount of

FIGURE 1 . Distribution of water needs during the vine’s vegetative cycle, with the total requirement being 100. Water stress during the fruit set-veraison period severely compromises seasonal production. Hence treatments with LalVigne ProHydro™ are recommended during this phase.

water required by the vine varies considerably during the different phenological phases (figure 1). This means that the consequences of water shortage differ considerably according to the development stage. The most delicate

* This article was first published in Italy in L’Enologo – Number 4, April 2022.

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TECHNICAL YEARBOOK 2023