Organic mulches improve vine vigour, yield and physiological response in a semi-arid region

The soil plays a pivotal role in the agroecological transition processes, due to its numerous implications in production support, water regulation, air and nutrient supply, and its function of reservoir for the major part of planet biodiversity. Therefore, soil quality and adequate soil management are key levers for an ecologically and economically sustainable viticulture. Gascogn’Innov (2017-2022) is an Operational Group funded by the European Innovation Partnership for Agriculture. As such, it gathered winegrowers from the south-west of France (Gascony), scientists, advisors and technicians, around a project focused on the biological functioning of viticultural soil and the design of better-adapted technical paths for soil protection.

Grapevine phenology has advanced across many regions, nationally and internationally, in recent decades under the influence of increasing temperatures, resulting in earlier
vintages (Jones and Davis, 2000, Petrie and Sadras, 2008, Tomasi et al., 2011, Webb et al., 2011. Earlier vintages have several ramifications for the wine industry. There are direct implications on quality, due to the fruit ripening during the hotter conditions of summer and early autumn, which then impacts grape composition and wine style (Sadras et al., 2013, Buttrose et al., 1971, Mira de Ordũna, 2010). There are also indirect implications where the fruit is perceived to ripen at a faster rate and the crop reach optimum maturity over a shorter period (Coulter et al., 2016).

The recovery of bioactive compounds from grape and wine by-products is currently an important and necessary objective for sustainability. Grape pomace is one of the main by-products and is a rich source of some bioactive compounds such as polyphenols, polysaccharides, fatty acids, minerals and seed oil. Polysaccharides contained in the grape cell wall can be rhamnogalacturonans type II (RG-II), polysaccharides rich in arabinose and galactose (PRAG), mannoproteins (MP), homogalacturonans (HG) and non pectic polysaccharides (NPP).

Aging on lees (AOL) has been used for wine aging for a long time, thanks to its ability to modify wine composition, improving sensory characteristics and stability. However, the prolonged contact with fermentation lees may increase the risk of developing sensory defects, due to the growth of unwanted microorganisms. Furthermore, AOL requires a large amount of work to manage bâtonnage and for topping up the barrels, significantly increasing production costs.

The wide diffusion of organic cultivation of vineyards and the need to reduce the use of pesticides highlights the urgent need for alternative and sustainable methods of vine protection by pathogen molds.