Is it really such a good idea?
Except in situations where root reservoir is subjected to high drainage (for instance sand situations) or when rooting depth is physically limited, common sense considerations make you wonder if this is really the best idea to adapt to drought and to get the best fruit quality out of your vineyard.
Here is why:
- Frequent re-wetting of the top soil promotes a shallower root system. After irrigation, top soil gets drier first compared to lower soil horizons. As a consequence, your vines favor more root distribution in the top soil but ask for more and more water once top soil gets dry after each small drink. When irrigation is applied several times per week, vineyard experiences a series of periods where water is very easily available and brutally harder to extract from the top soil. This negatively impacts photosynthesis.
- Frequent irrigation pushes the vine to behave like a hydroponic plant by disconnecting the root system from its intimate relationship to soil properties. As more roots develop in the top soil, your vineyard becomes more and more sensitive to the next irrigation, thus less and less resilient to drought. Because it “trains” your vineyard to be more dependent upon the next irrigation, we call it the “junkie” effect.
- “Terroir” effect tends to disappear and so does the unicity of your site. In arid conditions or during drier vintages, not only sciences but mainly empirical testimonials have emphasized how wine quality can be improved thanks to a moderate water deficit.
- Get inspired by “exceptional vintages”. The 2010 vintage in Bordeaux: after a full winter, refill of the rot profile was relatively dry from budbreak until mid June (50 mm rain) then dry again until mid July (20 mm rain) and dry again until early September (20 mm rain). Three “natural irrigations” made a “perfect storm” and drove an amazing maturation profile. Similarly, in more arid areas (Châteauneuf du Pape area for instance) a large “August storm” of 2-3 days after a dry July is classically attached to amazing vintages.
In the context of water scarcity and world wide competition for good wines, practices which optimize plant water use and fruit quality are becoming a necessity.