Smart Irrigation and Pruning Practices Reduce Heat Wave Impact on Yields


Team Terraview

Winemakers on the West Coast, from California to Washington, are being more proactive with future vintages after the recent heat wave that hit the Pacific Northwest areas of the United States and Canada in late June. Temperatures reached as high as 116° F in Portland, Oregon, 117° F in Salem, Oregon, a high of 118°F in Dallesport, Washington, and a scalding 121.3° F in Lytton, British Columbia.

Scientists predict the increase in atmospheric CO2 and other greenhouse gasses will increase the temperature of the planet from 1.5—4.5°C. While the full effect could take hundreds of years, some parts of the earth system—mountain glaciers, sea ice, precipitation—react within years or a few decades to a warming or cooling nudge. The previous decade, for instance, acted like a warming nudge; average temperatures from 2010 to 2019 made the last decade the warmest on record.

After years of battling these heat waves, as well as wildfires, smoke (California winegrowers, in particular, are assessing how much of their fruit crop suffered smoke taint from multiple blazes in 2020), and droughts that led to significant crop loss and earlier harvests, vintners have turned to smart irrigation for both pre-emptive and long-term canopy management. Unlike traditional irrigation controllers that operate on a preset programmed schedule and timers, smart irrigation controllers monitor weather, soil conditions, evapotranspiration, plant water use, and vine vigor to adjust the watering schedule to actual conditions affecting the vineyard.

Both Meyer Family Cellars, with its vineyards in Anderson Valley, Oakville, and Yorkville Highlands, and Constellation Brands in Napa Valley, with its powerhouse portfolio of wines, have turned to precision viticulture and new processes for help in managing the irrigation of their vineyards.

For example, according to a 2021 Corporate Social Responsibility (CSR) report1, the vineyards of Constellation Brands turned to new technologies to maximize water conservation to ensure that vines only receive “what they need, when they need it.” This includes minimizing over-watering, excess runoff, erosion, and unnecessary depletion of water supply, which they achieve through data-gathering mechanisms, such as soil monitoring devices and weather stations. As a result, Constellation’s collective Napa Valley vineyards used 51% less water than they did in 2018—100 million gallons less.

Warming temperatures have led to addition of newer wine geographies in the recent years

As the wine map expands to other countries like Georgia, Norway, Japan, Bolivia, and Canada, and as lands in established wine countries that couldn’t be cultivated for wine are opening up, these incorporeal journeys toward saving heritage vineyards that have long served their historic appellations hold an almost mystical quality to them. When one thinks of the power and hope that real-time, microclimate data offers to meet the rising demand for canopy management and yield predictions in a time of so much uncertainty and widespread panic to save these vineyards, even the most tech-weary among us can’t help but stop to reflect in appreciation.

Smart Irrigation Can Maximize Transpirational Cooling

Ideally, grapevines should be irrigated before an extreme heat event to maximize transpirational cooling of the grapes and prevent physiological damage. In a recent University of Illinois study2, a research team discovered 16% of a crop’s yield increase came from cooling alone. Irrigation, they found, cools crops through the combined effects of transpiration—the evaporation of water through tiny holes in leaves called stomata—and from the soil when there is a sufficient soil water supply. If roots sense dry soil, plants close their stomata to prevent water loss. If this happens long enough, the plant heats up and suffers drought stress, and eventually yield reductions.

TerraviewOS dashboard has water prescription maps to recommend the optimum irrigation as per the weather and phenological cycle

Irrigation is only one variable in a complex, multi-factor system of approaches and solutions. The effects of extreme heat on grapevines also vary, depending on the timing of the heat event relative to the developmental stage or phenology of the grapevine. The young grapes in Oregon and Washington could have received damage to the fruit surface or ripened too early or even aborted the plant from the recent heat wave, but a very wet June and the event’s occurrence over a narrow window in the veraison stage prevented damage from taking place.

Rising Temperatures Affect Wine Quality and Pruning Choices

Warmer places like France, Italy, and Spain are no strangers to higher temperatures that have spoiled wine quality because of over-ripening and greater vulnerability to pests and diseases. Rising temperatures have changed the taste, color, and phenol concentration of wine itself. While grapevines can sometimes thrive in poor soils or marginal climates, the higher temperatures and the water loss mean the berry will ripen with more sugar and less acid, and consequently will produce wine with higher alcohol content. The best-case scenario would be to harvest the crop at or before the peak of sugar accumulation. In the foothills of central Italy, for example, the grapes used for Chianti Classico are reportedly dehydrating and ripening too fast under the blistering sun. Getting the harvest date right, along with good canopy management practices, could mean the difference between another successful wine yield or a raisin crop.

The change in ratio of anotcyanins to tannin due to rise temperature affects the ‘fineness’ of wine

The upshot of extreme summer heat on farmer confidence is that they have become more timid in the pruning of their vines during winter pruning operations to prevent bunches from overexposure to sunlight in spring and summer. Pruning non-productive shoots is especially important to achieve a balance between yield and vegetative growth in the following season. Among the benefits include keeping the grapevine productive by removing unwanted shoot growth which can cause shading and hinder spraying, improving air circulation to reduce powdery or downy mildew infections, vine vigor, and fruit quality. Some farmers even argue that eliminating vegetation (productive or not) is essential for vine vigor. At the very least, pruning non-productive shoots will help the trunk and vines retain their shape every year.

Precision Viticulture Tools Aid in Health and Vigor of Vineyards

After a heat wave event, a farmer will scout the vineyards for pests, plant diseases, and nutrient deficiencies, as stressed plants are more susceptible to pests, diseases, and root rot. One of the easiest ways to identify plant diseases and nutrient deficiencies is through the Vine Click app by TerraviewOS. This app makes identifying and diagnosing plant diseases and nutrient deficiencies much easier with just one click of the mobile phone’s camera.

TerraviewOS also captures hi res imagery through satellite such as MAXAR’s True30 and using proprietary image processing algorithms generates insights to help vineyard owners assess the health and vigor of a plantation over the season and plan corrective actions like smart water usage.

Got questions about how TerraviewOS can help you manage your vineyard with the rise in temperature?
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