Do grape vines need irrigation ?
In this current context of drought, the debate has come front and center in many parts of our planet. Opinions, often formulated with absolute certainties, are often linked to past weather patterns and whether or not there is enough access to fresh water for irrigation.
In our Mediterranean climate, the grape vine is one of the cultivated plants with a low demand for water. But like all plants, a grape vine needs water for its photosynthesis, for the building of its tissues, for feedings its fruits and in order to regulate its temperature.
Until now, in most of France, the annual rainfall, measured both in quantity and distribution over time, was sufficient to ensure the healthy development of the grape vine. The soils were able to store enough water during the winter period to make it available to the roots during the dry season.
Unfortunately, the dry-farming vines in our region is endangered today because of two effects :
o Firstly, the depletion of our soils’ organic matter since the advent of mineral fertilizers. This organic matter, combined with the clay in the soil, forms the “clay-humus complex” : a veritable sponge and biomass support, storing water and minerals made available to the plant.
o Secondly, climate change, with its sharp decrease in annual rainfall over the past 25 years, its increasingly frequent droughts that last significantly longer, and its protracted heat waves have made naturally occurring water scarcer than ever in our modern period.
The result is that our soils have a much lower water retention capacity than 50 years ago, and the problem is growing more acute.
Regenerative agriculture responds to these two issues cultivating permanent cover crops between the rows of vines. This will substantially improve its soil’s organic matter.
However, an old French adage says “you have to sow before you can reap.”. When moving from tilling to no-tilling with covered soil we’ve actually increased the need for water. Indeed, the cover crops compete with the vines by drawing water from the soil.
However, over the next 3 to 5 years, the cover crops will increase the rate of organic matter in the soil and will therefore increase its water retention capacity. Ultimately, our goal is to no longer irrigate our vines, or as little as possible. This is why we have chosen to irrigate our vineyards with cover crops in the short-term.
We benefit from the Bas-Rhône Languedoc Irrigation Canal. The canal, designed to supply regional farmers, is a source of fresh water from the Rhône just before it empties into the sea. Of course, we have chosen the most frugal method of water distribution: drip irrigation. We also make it our mission to meet the needs of the vine as accurately as possible with the help of modern technologies : soil capacity probes, observation by leaf pressure chambers, as well as weather stations in our vineyards. By controlling the level of water stress in the vine, we maintain optimum grape quality.
The other important benefit of this approach is that by increasing organic matter in our soils we can actually trap more carbon from the atmosphere and bury it beneath our feet thanks to the photosynthesis of cover crops. This is just one example of how we farmers can contribute to reducing the greenhouse effect which is playing such havoc with our environment worldwide.
At our own level, we’re trying to do what we can for our planet…