Dry farming has become a topic lately and we thought you would be interested to hear from someone who did both – dry farming back in Switzerland and drip irrigation here in sunny Marlborough.
The presence of water is essential for the survival of all plant life. In a grapevine, water acts as a universal solvent for many of the nutrients and minerals needed to carry out important physiological functions, and the vine receives these by absorbing the nutrient-containing water from the soil.
To protect wine quality, irrigation is illegal in some of the world’s best wine regions, particularly in Europe like Burgundy, Bordeaux, Barolo, Barbaresco, and Brunello. A look at the average rainfall for many of those regions, however, shows that they typically get plenty of rain. Irrigation was banned in these regions not because it necessarily makes inferior wine, but because excessive or ill-timed water, whether rainfall or irrigation, can result in diluted wine (or too much vigour). Without such a law, some producers might irrigate to plump the grapes with water, decreasing quality to increase quantity.
On the other hand, there are many very fine wine-growing regions where irrigation is legal. Simply put, some regions would not sustain vineyards without irrigation including many great terroirs in sunny and dry Marlborough. Our vineyard for example, gets only an annual precipitation of 637 mm. The soil makes a huge difference too. Some subsoils, especially limestone (Burgundy), chalk, and clay (our hillside vineyards in Switzerland), will hold significant amounts of water, for vine roots to sip, as needed. Unlike our well-draining gravelly, sandy soils which are not able to retain water (or fertilizer).
Timing of rain is crucial. Fortunately, Marlborough’s Wairau valley gets most of the rainfall in winter and early spring, which is ideal, not during the grape growing season unlike many of the famed vineyards in Europe. Rain is not welcomed when bunches are already fully developed dampening leaves and grape bunches, encourage rot or other diseases from excess moisture on the vines. (Unlike drip irrigation where water goes directly onto the soil.)
Wairau River, adjacent to Hans Herzog Estate
One of the most famous vineyards in the world, Cheval Blanc in St. Emilion (mostly gravelly sandy soils like ours), would love to have irrigation in dry years because the heat and drought are retarding the phenolic maturity. With climate change, even some traditional strongholds of dry farming are relaxing their regulations. In Barolo and Barbaresco, the Italian Ministry of Agriculture allows irrigation on a case-by-case basis because warming has led to severe dehydration at certain times during recent vintages, significantly affecting wine quality.
In Marlborough, most vineyards show drip irrigation unless in wet areas or on cool clay soils which retains water much better (e.g., Hillsides). Ideally and for high quality wines, drip irrigation applies water in very small amounts over a limited period to simulate a light rain. As water soaks into the soil, it forms spherical zones of moisture beneath the vines, rather than being spread out over the entirety of the vineyard, encouraging the roots to grow downward. For quality wines like ours, watering is only done when the vines show need and only in the necessary volume at night, when vines are most eager for replenishing and evaporation is minimized.
Unfortunately, where quantity is wanted, irrigation is often constantly on and vines get accustomed to easy water and have only shallow, horizontal roots. Those will not be able to reach a receding water table, and the topsoil in which these roots reside would dry out quickly. They also miss the underlying nutrients in deeper layers making complex wines. Irrigation systems can also deliver liquid nutrients (as opposed to spraying), often needed for vine health when producing large yields.
Back in Switzerland, our hill-side vineyards consisted largely of water retaining clay soils. With an annual precipitation of 1086mm and more than wished for rainfall during the growing system, there is no need to spend money on an irrigation system. In Marlborough, our vines on the gravelly, sandy soils would suffer and quality would be affected with our dry summers and weeks without rainfall. However, it becomes one of the world’s best climate for growing wine with an average of 2507 sunshine hours per year once access to water is assured.
Looking at sustainability, water for irrigation should be available naturally. Our plot of dirt came at a high price, even back in the early 90ties, because it came with bores accessing the deeper water aquifer of the neighbouring mighty river. It does become questionable when cheap land, without natural water access in remote areas, is bought for intense agriculture (any) and massive amounts of water transported from far away, depleting dwindling water sources and causing land destruction through expansive piping.
At the end of the story, lower yields make better-quality grapes. Irrigation is a tool and like any tool, it can be used well or badly. Wines of high and low quality result from irrigated and non-irrigated vineyards alike. It’s what is in the bottle that counts, isn’t it…
More on that topic - https://daily.sevenfifty.com/3-myths-about-irrigation-and-dry-farming/