Will the drought sap wine-growing?

Agricultural production system must be transformed so that they use soil, water and energy resources sustainably, and reduce the use of water, fertilisers and pesticides. Anticipate in order to better adapt: that’s the challenge of the wine-growing sector in the Adour Garonne basin that IFGR’s members were able to ascertain during the last session.

The basin has numerous wine-growing areas (Bordeaux, Cahors, Cognac, Gascogne, Fronton, Gaillac, Bergerac, etc.). With 120,000 ha of vines and an average vineyard age of 36 years, wine-making remains a major economic activity in the Bordeaux region and an important part of its heritage. What impact will rising temperatures have? Are we heading for irrigated vineyards?

Do grapevines need water?

Adapted to high temperatures, grapevine is highly resistant to hydric stress. Traditionally, the vineyards of Bordeaux have not been irrigated and tolerate heat very well. For 10 t/ha of grapes produced, only 300 to 400 ml of water are needed versus 1,600,000 ml to cultivate 1 kg of rice!

The root system of grapevine is capable of delving deep into the soil to find the moisture it requires. However, the quantity of water it is capable of obtaining acts on yield and quality. The grapes will ripen under more summery conditions. The overall composition, balances between sugars and acids, and aromatic compounds and phenols, on which the type and quality of wines produced, risk being significantly modified. Finding the right level of hydric stress is crucial to the goal of adapting to climate change.

Solutions for tomorrow

Irrigation is obviously seen as a means of efficiently mitigating the effects of drought and can, in the short term, ensure yields without impacts on quality. Many vineyards in France and elsewhere in the world are irrigated or becoming so. The Société du Canal de Provence has, for example, concluded a partnership with the wine cooperatives of Côtes de Provence and Coteaux Varois and the IGP du Var to develop its irrigation network over 20,000 ha of vines for an investment amounting to €250 million, in part paid by the sector.  But in the long-term, implementing this practice alone is risky: it is subject to legal constraints, expensive and non-sustainable as tension over water resources is increasing. It will be necessary to utilise and combine several modes of adaptation: the selection of new varieties and root stocks, modification of cultivation methods (staggering harvests, changing wine-making methods, etc.). Attention must also be given to soil quality and spatial distribution: the spacing of plants and the height of rows may provide natural shade for the fruit which would better tolerate heat.

Develop smart irrigation, as well as other solutions 

Testimony of Michel Delaere and Isabelle Dupouy own the Les acacias, a small company specialised in producing Côte de Gasogne wine and Armagnac, both protected by local labels, at Bezolles in Gers (32).

“The major drought periods that struck from 2011 to 2013 had an impact on the quality of our productions, leading to a loss of income. This triggered our search for “smart” irrigation, which resulted in 2015 in the installation of 88 km of piping to supply water drop-by-drop. The water is pumped from the river across the valleys to the feet of the vines. This installation, which is controlled regularly and capable of predicting the needs of the plants for water and nutrients, has allowed us to renew 7 ha of “new” and organic vines on our 28 ha to replace the part damaged by drought and diseases.

We also changed to mechanical pruning to give the grapes more space and give them denser foliage to provide shade and protection against the sun’s rays and the rain. We planted almond trees and organic mustard to protect the vines against strong heat and provide them with the nutrient elements they need to thrive. Agri-forestry promotes the well-being of the vines and the development of biodiversity (birds, insects, etc.), in fact a virtuous circle. We’ve already been using biocontrol products to protect our vines from diseases for 17 years.”