VINEYARD IRRIGATION: Grape Growers Weigh Best Practices to Yield Best Crops While Keeping Tabs on Water Conservation

By: Cheryl Gray

  In the universe of viticulture, the letters “E.T.” do not stand for “extraterrestrial.”  Vineyard consultants and growers use the acronym to describe the sum of evaporation of water from the soil surface plus transpiration (water loss) from the leaves of grapevines. Where there are deficiencies in natural water supply, vineyard irrigation is critical. In some grape growing regions, though, it is also controversial. As a result, vineyards are forced to strike a balance between water usage, costs to dispense it, and investment in new technologies aimed at optimizing water management.

  There is a vast array of science that goes into the process of vineyard irrigation. Grape growers often turn to those who have studied the field and know precisely how to choose the right method of distributing extra water to grapevines to produce the best grapes.

  Not many know more about the science of vineyard irrigation than Dr. Lowell Zelinski of Pasa Robles, California-based Precision Ag Consulting. His three decades of experience, along with a doctorate in soil science from the University of California-Davis, make him a trusted authority in vineyard management, viticulture production consulting, soil fertility and irrigation management throughout California’s Central Coast and San Joaquin Valley.

  As a plant physiologist with detailed knowledge of the relationship between soil, water and plants, Dr. Zelinski helps vineyard growers reach their production goals with one-on-one consulting, which includes deploying a combination of traditional methods and cutting-edge technology. Since most of his clients operate vineyards in a region where water supply is at a premium, there is not enough water flow for sprinklers, not to mention a topography that defeats any chance for successful furrows. Hence, drip irrigation is the choice. 

  Dr. Zelinksi points to monitoring as an important element of any vineyard irrigation system. “Most have or will have soil moisture monitoring stations. They also have weather stations, and, as needed, we use a leaf porometer.”  

  Therein lies part of the science—the “E.T.” factor—so critical to vineyard irrigation. A porometer measures water stress in a grapevine, specifically, its leaves. The device gauges how much water the grapevine leaf is taking in through the small pores on its surface. If there is too much water evaporation from the leaves, they will wither. When leaves on a grapevine show signs of stress, the rate of evaporation and the ability for the plant to cool itself drops. The leaf porometer allows grape growers and their consultants to keep tabs on this process.

  Another crucial factor in vineyard irrigation, Dr. Zelinski says, is monitoring vineyard soil conditions. 

“Soil moisture monitoring is important because it gives an objective measure of how much water is in the soil at different depths,” he says. “Additionally, with the correct soil probes, the strength with which the soil is holding onto the water can be determined. This indicates how hard the vines need to work to extract water from the soil. Monitoring at different depths also indicates whether or not the soil is being over-watered or under-watered.”

  While the application of extra water in the cultivation of wine grapes takes on more than one form, the goal of controlling water stress is universal. To strike this balance, the grapevine receives adequate water during the budding and flowering stages. Irrigation is then scaled back during the ripening stage, thus allowing the vine to channel most of its water into developing grape clusters, instead of growing more leaves. In the drier regions of the United States, vineyard irrigation is indispensable, and drip irrigation is the method of choice.

  Some vineyards are fortunate enough to be in a climate where water stress is rare. Such is the case for Black Star Farms, whose vineyards are located in northern Michigan, near the resort community of Traverse City.

  “We really only irrigate in the early stages of a vineyard’s life, when young plants need plenty of water to get a healthy start,” says Lee Lutes, winemaker and managing partner at Black Star Farms. “We often see a little drought in early to mid-summer, and with our well-drained soils, it’s the time those young vines need the help. We only use drip irrigation as a means of monitoring how much is dispensed to each plant and to specifically focus it. After year three, the system is typically never used again.  We are fortunate that we get more than enough water during the spring and fall, so vines in our region rarely show signs of water stress.”

  On the opposite end of the 45th parallel is Washington’s Two Mountain Winery, a name inspired by the views of Mount Adams and Mount Rainier, seen from one of the winery’s multiple vineyards in Yakima Valley. Brothers Matthew and Patrick Rawn own and operate the winery. Patrick Rawn is the general manager and spearheads vineyard operations. He says Two Mountain Winery has used a mix of irrigation methods.

  “We use drip on the vast majority of our acreage. We have a few blocks with micro-sprinklers that were installed to allow for planted cover crops to help achieve crop objectives. In those blocks, we also have drip systems to irrigate the vines,” says Rawn. “We have had mixed success with micro-sprinkler systems. The early ones installed were poorly designed and did not achieve the goals. The newer ones achieve the goals but at the cost of more water usage. We have found drip to be the most efficient as well as most effective in reaching our quality objectives. Choices are based on site characteristics, water source and intention of the block when planted.”

  Rawn adds that it is important to know what is happening in real-time through consistent monitoring, especially when it comes to checking moisture levels in the soil. Two Mountain Winery checks soil conditions through a five-minute communication cycle using soil moisture monitoring probes.

  “Knowing the actual soil moisture relative helps us achieve quality objectives and reduce irrigation applications,” Rawn says. “Additionally, we can more efficiently focus our irrigation labor budget on areas the sensors communicate are out of our parameters. I have a much clearer understanding of our soil variations and how to more precisely deploy irrigation resources since we first deployed the sensors.”

  Rawn says Two Mountain Winery uses a system supplied by the Wilbur Ellis Company, a century-old global leader in agriculture technology, which has some 30 vineyards on its client roster throughout California, Oregon and Washington state. Its most popular products are its electronic probes and telemetry, both of which are run through the Wilbur Ellis Probe Schedule dashboard. The company attributes the popularity of the Probe Schedule to its ease of use, noting that vineyards can, at a glance, make water management decisions, quickly and easily. The Probe Scheduler has an open API to share data easily.

  “The information is easy to digest and read and has good ETC modeling and water budgeting tools,” Rawn says. “We purchased [it] as a service, which we prefer. We are not responsible for maintaining the equipment or software upgrades. We rarely experience downtime, but not spending time troubleshooting sensor problems when they arise is a big plus.”   

  On a smaller scale, there are other companies with innovations on the market touting significant results, such as California’s Deep Root Irrigation, which invented an independently tested, patented technology designed to curb water waste and maximize plant growth. Company owner Jeremiah Ciudaj tells The Grapevine Magazine that the DRI system is groundbreaking, in part, because it delivers water and nutrients directly to the plant root. 

  “This simple, affordable device connects to an existing drip emitter on one end, while the other end of it inserts vertically into the ground for water and fertilizer delivery directly to the root zone,” he says. 

  Globally, the viticulture industry is using new technologies to improve vineyard irrigation in regions all over the world, particularly in areas where climate and soil conditions are not optimal.  At the same time, vineyards are mindful of water conservation, if for no other reason than to hold down costs and, in the case of drier climates, avoid over-consumption. The trend toward drip systems, combined with technology designed to provide instant data on water management in vineyards, helps to contribute toward containing energy costs, as well as preserving water, thus keeping vineyards ever mindful of the invaluable natural resource that is water. 

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