Danielle Venton, WIRED
California’s Central Valley farmers have a problem. Agriculture accounts for about 80 percent of the state’s water consumption, and in the midst of a historic drought, it is the largest potential source of water savings. Farmers want to be good stewards of the land by helping save water—it is, after all, what sustains them. But there’s a limit to what they can eke out of the soil with the water governor Jerry Brown has given them to work with.
Or maybe there isn’t. New irrigation techniques have made it possible to increase yields with less water than farmers once thought they needed. It’s even possible to farm essentially without water—growing produce by using the water and fertilizing nutrients already in the soil.
In Templeton, California, Mary Morwood Hart is using dry farming on her Grenache, Mourvedre, and olive trees, carefully cultivating the soil on her 20 acres so it can sustain growth without water. Over the past century, US agriculture has pushed itself to produce higher and higher yields by carefully engineering its plots: building larger farms with more advanced mechanics and increasing reliance on fertilizers, weedkillers, and pesticides. That’s brought more food to market. But it’s also depleted the soil—those steps tend to kill the microbes that build organic material and make it sponge-like.
Hart and other dry farmers think they can find a solution in the dirt itself. When soil is left to its own devices, it becomes rich in organic material. It loses less water to runoff and evaporation, and food can grow with little or no irrigation.Increasing soil organic content in an acre of farmland by just 1 percent can save up to 27,000 gallons of water.
That’s especially true of grapes. Hart and her husband, who run the farm together, believe dry farming prolongs the vine’s life, and their method isn’t exactly devoid of moisture: The calcareous clay soils in Templeton, she says, hold a lot of water. “It creates a situation where the tap roots have to dig deep down into the soil to find moisture and it brings about character and a complexity of flavor,” says Hart. “When you do irrigate a vine, the roots tend to grow very close to the surface, because they’re just waiting there for their drops of water.”
The downsides are what you might expect: Dry-farming reduces the weight of the grapes, so the farm’s overall output is lower than average (typical output is four to six tons per acre, while Hart gets a measly 1.3 tons). But without irrigation, her plots are less expensive to tend to and easier to grow on hillsides. And old vines and the smaller grapes that grow on them are prized for their flavor—which she can charge a premium for.
At Molino Creek Farms on the Central Coast, grower Joe Curry raises dry-farmed tomatoes on 136 acres. He and the other farm founders chose dry farming because their land has very little access to water. Once his tomatoes are taken out of the greenhouse and planted in rows, they receive no additional irrigation. That’s only possible, he says, because the farm takes care of the soil. Prior to planting they mow cover crops, leaving them on the ground to decompose. The nutrients re-enter the soil, used to support the next season of growth.
The effect on water usage is dramatic. According to the National Resource Conservation Service, an arm of the US Department of Agriculture, increasing soil organic content in an acre of farmland by just 1 percent can save up to 27,000 gallons of water. (Other estimates are less hefty, but still impressive.)
But waterless agriculture isn’t the answer for everyone. Tomatoes, grapes and vegetables are relatively high-value crops—not all farmers can afford sacrificing their high yields for higher quality. And certain crops like lettuce would taste terribly bitter if dry farmed. So other farmers have turned to other methods to conserve water.