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As California Drought Lingers, Tule’s Sensors Guide Crop Irrigation

Xconomy San Francisco — 

Californians have been using their garden hoses sparingly to help conserve water during one of the state’s driest years in history. But what if you’re a farmer with acres of crops that need irrigation to grow, and you learn that the state may curtail water supplies for agriculture?

Tom Shapland has been thinking about the challenges of farming since he was an undergraduate at U.C. Davis majoring in viticulture and enology—fancy words for growing grapes and making wine out of them. He says he quickly realized what really mattered to all farmers, even in years with normal weather.

“The bottom line is water,” Shapland says. “It determines the crop yield and the price per pound of produce.”

As a PhD student at Davis in horticulture and agronomy, Shapland learned about a sensor technology that might help farmers calculate more precisely how much water is actually needed to irrigate a whole field, without either wasting water or curbing crop growth. But the system, conceived by his PhD advisor, U.C. Davis professor of atmospheric science Kyaw Tha Paw U, needed some tweaks because it would otherwise have been too expensive to become a viable commercial product.

Tom Shapland

Tom Shapland

Together with Dr. Paw U and other U.C. Davis atmospheric scientists, Shapland worked out the technical hitches for his PhD project and graduated in 2012. He then teamed up with software engineer Jeff LaBarge to co-found San Francisco-based Tule Technologies in 2013, with an exclusive license from U.C. Davis to commercialize the sensor system.

Things moved fast for them in 2014. They were accepted into the summer class of the accelerator program Y Combinator, which invested $120,000. Tule attracted other investors including Menlo Park, CA-based Khosla Ventures, Bloomberg Beta, and other angel investors, to raise a total of more than $1 million.

Tule’s sensor devices are now scattered in scores of fields from Oxnard, CA near Los Angeles to Mendocino County in Northern California. The equipment looks something like an orange plastic briefcase on a pole, with a chicken wire halo.

The sensors beam data from the fields to Tule via cellular networks, and growers log in to a dashboard to learn how much water has vaporized into the air from their vineyards or fields of strawberries or tomatoes. This tells them how much water they need to replace through irrigation in the next few days.

This is a high-tech, remote-controlled alternative for farmers who would otherwise have to drive out to evaluate each field with a tool that measures soil moisture in a few sample inches within the plot, and another instrument that assesses the health of one individual plant at a time, Shapland says. A Tule sensor can capture relevant overall data for a whole field as large as 10 acres, he says.

A Tule sensor, shielded from birds by the chickenwire cage, measures fluctuations in temperature as individual eddies of wind blow by, bearing the water vapor “exhaled” by the plants in the field. It’s easy to think of plants mainly as water consumers, soaking up moisture from the soil through their roots. But as plants make use of the water they’ve drawn in, they also release water vapor from tiny pores in their leaves through a process called transpiration.

This vapor accounts for most of the water lost to the atmosphere from farm fields, Shapland says. Evaporation directly from the soil itself amounts to a small percentage of the total water loss, which is called evapotranspiration.

From the field data, Tule derives a group of measurements. Total evapotranspiration is a gauge of the crop’s water use. Tule’s equipment is also connected to the farm’s irrigation system, so it clocks the amount of water applied to the field. With a little math, Tule calculates how thirsty the plants are—a measure called the “water stress level.”

Factoring in weather conditions, Tule sends the farmer a recommended irrigation plan for the field through its dashboard and via e-mail. Ideally, the plan would spare growers the expense of applying more water than is needed, only to have it sink down through the soil below the root zone to be wasted, Shapland says.

By mid-2014, when Tule was part of the summer class at Y Combinator, the company had about 40 customers in California paying for data from 100 sensors, Shapland says. Rather than selling its equipment, Tule retains ownership of its sensors, handling the installation and maintenance. What Tule sells farmers is a data subscription for $1,500 per sensor per growing season. For perennials such as fruit trees, that growing period would be about a year.

“The grower just wants the information,” Shapland says. “They don’t want to have another piece of hardware they have to install and maintain.”

Shapland says he knows of no competitor with a similar capacity to take the field measurements made possible by the U.C. Davis inventions. Tule, with five employees including Shapland and chief technology officer LaBarge, now has 60 customers deploying 250 sensors.

Many of Tule’s customers belong to the California wine industry, where Shapland has both an educational background and work experience. Those customers include  Constellation Brands, a leading seller of premium wines including the Napa brands Robert Mondavi and Clos du Bois; Chateau Montelena Winery; Matthiasson Wines; Beckstoffer Vineyards; and Atlas Vineyard Management. Tule now has 60 customers deploying 250 sensors.

The company is just beginning to learn how its data might some day empower growers to make management decisions, such as the choice of irrigation methods or the scheduling of water delivery during the course of the day or over the growing cycle, Shapland says. But the potential is there, he says.

For example, growers may not always want to fully replace the water lost through evapotranspiration.

“There may be a window in (plant) development where being a little water-stressed can be beneficial,” Shapland says. The cells of wine grapes may tend to produce more flavor compounds if they’re a little thirsty, he says. Similarly, if almond trees are a bit water-stressed close to harvest time, the hulls enclosing the nuts tend to crack. Workers can then shake more nuts out of the trees, he says. Tule hopes to start working with almond growers next year, Shapland says.

“We want to bring the technology out to more growers,” Shapland says. “There’s a lot of good it can do for a lot of people.”

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  • AMS

    In Tuscany, dryfarming is required.
    Hint hint, California…