The effects of shading nets in vineyards have been studied extensively, and this review aims to assess the consequences of using artificial shading on grape production.
Introduction
Viticulture worldwide is threatened by the environmental modification caused by climate change. Higher temperature and atmospheric CO2 concentration determine an acceleration of the ripening process, which can be detrimental to wine quality. Hence, adaptation and mitigation strategies are necessary to reduce heat and water stress and improve qualitative production levels. Amongst all the various techniques available, shading nets represent an interesting alternative for their effects on canopy microclimate and grape production. However, these effects vary strongly depending on the intensity of the shading treatment, the timing of its application, environmental conditions, and differences in cultivar response.
Effects of using shading nets
The reduction in light intensity lowers the photosynthetic activity of the canopy, leading to the lower production of photoassimilates. Whereas the effects on vine yield appear variable, grapes benefit from a lower exposure with a reduced incidence of sunburn, berry dehydration and cell death. By lowering carbon assimilation, nets provide a slowdown of the ripening process, leading to a lower concentration of sugars in the musts and less alcoholic wines.
In general, the organic acid content is increased by netting due to the containment of their depletion, and must pH is usually lowered. Phenolic concentration is mostly decreased by shading since the reduction in light intensity affects the genetic pathways that lead to their biosynthesis, altering the quantity and the proportions of these compounds.
The effects on the aromatic components seem rather variable depending on the environment: in warmer climates, where temperature can reach high values determining their volatilisation, net shading improved the aromatic profile of musts and wines by preserving them, while in cooler climates, it seems that grapes exposure to sunlight might increase their production.
Reserve accumulation is influenced by the reduced production of photoassimilates, and the constriction of dry matter partitioning seems to take place mostly at the expense of the roots.
Photoselective nets
Thanks to their combined protection from adversities and filtration of determined regions of the light spectrum, photoselective nets represent a new horizon in the research on this topic. Because of their colour, they not only reduce light intensity but also change the quality of the light spectrum reaching the canopy, ensuring a wide range of results in relation to the types of nets used and the response of the various cultivars.
Conclusion
Using artificial shading represents a valid alternative in viticulture to mitigate the effects of global warming. Albeit with some differences related to the period and method of application and the intensity of light reduction, at the expense of a reduction in the accumulation of reserves, it allows to slow down the ripening process, prevent the volatilisation of the aromatic compounds and reduce the damages caused by bunches overexposure.
Reference
Pallotti, L., Silvestroni, O., Dottori, E., Lattanzi, T., & Lanari, V. (2023). Effects of shading nets as a form of adaptation to climate change on grapes production: a review. OENO One, 57(2), 467–476. https://doi.org/10.20870/oeno-one.2023.57.2.7414
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