National Geographic Society Newsroom

California Dairies Join Forces with Conservationists and an Irrigation Supplier to Save Water and Reduce Groundwater Pollution

For most of us, dairy products like milk, butter, cheese, and yogurt are an integral part of our daily diets. In fact, US residents consume on average more than 600 pounds of dairy products (expressed on a milk-equivalent basis) per year, according to the US Department of Agriculture. Some 9 million dairy cows meet that...

Conservationist John Cardoza (left) and dairy manager Nate Ray check on feed corn fertilized with dairy wastewater delivered through an innovative drip irrigation system. Photo credit: Paolo Vescia

For most of us, dairy products like milk, butter, cheese, and yogurt are an integral part of our daily diets. In fact, US residents consume on average more than 600 pounds of dairy products (expressed on a milk-equivalent basis) per year, according to the US Department of Agriculture.

Some 9 million dairy cows meet that demand, and growing their feed and quenching their thirst consumes a great deal of water. To produce and bottle just one cup of milk can require some 55 gallons (208 liters) of water.

So as the recent five-year drought deepened in the state of California, which produces one- fifth of the nation’s milk, dairyman Nate Ray got a bit worried. Ray is the general manager of De Jager Farms, a 17,000-acre (6,880-hectare) operation in the San Joaquin Valley just north of Fresno that grows alfalfa, corn and wheat to feed some 25,000 dairy cows.

The dairy faced the challenge, Ray explained, of how “to continue to farm the same amount of acreage that we had in the past with an ever dwindling water supply.”

Most dairy producers irrigate and fertilize their feed crops simultaneously by flooding their fields with nutrient-rich water from their manure lagoons – ponds that store the wastewater from cleaning cow stalls. Each cow produces some 100 pounds (45.4 kilograms) of manure a day.  This manure provides valuable nutrients for crop growth, and, if applied to fields in the proper quantities, can create a virtuous nutrient cycle that reduces or eliminates the need for chemical fertilizer.

But with most dairy farmers flooding their fields with lagoon water, both more water and nutrients typically get applied to fields than the crops require. The excess nitrate in the manure can potentially run off or leach into the groundwater below, where it can pose health risks.

After solids are separated out of dairy manure, the liquids end up in lagoons like the one above at De Jager Farms in California’s San Joaquin Valley. This liquid fertilizer is pumped out of the lagoon, filtered to remove particles that could otherwise clog irrigation lines, and fed into an underground drip-irrigation system. The innovative system can increase yields while saving water and protecting groundwater from nitrate contamination. Photo: Paolo Vescia

To save water during the drought, Ray began experimenting with drip irrigation, which delivers a precise amount of water directly to the roots of crops, a big contrast to flooding the whole field. Especially when the drip lines are placed below the land’s surface, drip irrigation can save a great deal of water, while often increasing yields. Farmers get more crop per drop, which helps sustain their groundwater reserves.

After three years of irrigating an 80-acre alfalfa field with a subsurface drip system, Ray started reaping significant yield increases as well as savings in both water and labor.

But there was one big problem: the nutrient-rich, manure water would clog the drip system. So for Ray to save water by shifting to drip irrigation, he’d have to apply chemical fertilizer rather than his cows’ manure, which would hurt both his bottom line and the environment.

Enter Sustainable Conservation, a non-profit organization based in San Francisco, and Netafim, a global leader in the development and marketing of drip irrigation technologies.

Together the three partners piloted an innovative solution: a subsurface drip system able to deliver just the right amount of irrigation water and nutrient-rich manure to the dairy’s feed crops.

“Nobody has really been able to accomplish that in a commercial way,” says Dennis Hannaford, a Fresno-based product manager with Netafim.

The system Netafim designed filters the lagoon water to prevent clogging and uses electrical conductivity sensors to automatically balance freshwater and lagoon water so as to maintain a constant water quality. The goal is consistent application of nutrient-rich manure water to the field.

With precise delivery of liquid dairy manure mixed with fresh water through buried drip lines (pictured above), De Jager Farms and other dairies can deliver water and nutrients directly to the crop’s root zone, increasing both water and nitrate use efficiency. Photo courtesy of Sustainable Conservation

A 2015 pilot of the system on a 40-acre (16.2-hectare) field of silage corn at De Jager Farms produced stellar results. Water use efficiency increased by 38 percent, nitrogen use efficiency by 52 percent, and corn yield by 15 percent.

While saving water was Ray’s initial motivation, the reduced leaching of nutrients into groundwater could have broad societal benefits if more dairies adopt this innovative system. All human and animal waste contains nitrogen, which is a vital nutrient but can become a health risk if too much enters drinking water. The federal Environmental Protection Agency sets a limit of 10 milligrams of nitrate and 1 milligram of nitrite per liter of drinking water to guard against health hazards, including blood disorders in infants.

A 2012 study by scientists at the University of California-Davis found that nitrate contamination of groundwater is widespread in the four-county Tulare Lake Basin and the Monterey County portion of the Salinas Valley, an area that represents about 40 percent of California’s irrigated cropland and over half of its dairy herd. The application of synthetic fertilizer and animal manure to cropland is the leading cause of nitrate contamination of groundwater in the region.

Roughly 254,000 people in the five counties studied are currently at risk for nitrate contamination of their drinking water, according to the research team, which was led by Thomas Harter and Jay R. Lund. Moreover, the communities in the region are some of California’s poorest and so least able to pay for additional treatment or alternative drinking water supplies.

Dairy cows typically produce some 100 pounds of manure a day. If managed well, this manure can be a valuable fertilizer for the cows’ feed crops. If applied in excess, however, nitrates from the manure can leach into groundwater. Photo courtesy of Sustainable Conservation

With concerns about groundwater depletion and nitrate contamination on the rise in California and other parts of the country, the drip-manure system being piloted at De Jager Farms holds promise.

“The yield increase, water savings, less reliance upon commercial fertilizer, less ammonium emissions, and less leaching of nitrates into our groundwater, are all goals that can be obtained,” said Ray, the farm manager, in an email exchange. “It just needs to be seen by farmers with their own eyes.”

Ryan Flaherty, director of business partnerships with Sustainable Conservation, agrees. “We typically spend a lot of time showing farmers the business value of practices we’re promoting, but with this system they already get it. They’re actually asking for it. That’s incredibly exciting.”

This year Sustainable Conservation and its partners expanded the pilot to three other dairies in order to test the system under different soil types and management practices. All together some 257 acres (104 hectares) in Kern, Madera and Merced counties will be irrigated with the drip-manure system and monitored for three years.

The expansion of the pilot was made possible by a Conservation Innovation Grant of $833,000 from the US Department of Agriculture (USDA), a program designed to test promising methods for improving agriculture’s productivity and sustainability.   (Note: matching funds were provided by Sustainable Conservation, which included a contribution from Change the Course, thanks to our corporate partners DanoneWave and Disney.)

“With improved water use efficiency, higher yields, and a reduction in nutrient leaching, we hope the three new projects will demonstrate the positive results we have seen in the pilot and lead to increased adoption of these systems,” said John Cardoza, project manager with Sustainable Conservation.

If those benefits pan out, Sustainable Conservation hopes USDA will make the drip-manure system one of its standard conservation practices, a designation that provides federal cost-sharing for farmers who adopt it – helping spread the practice and all it offers.

“Imagine the enormous benefits to the health of our environment, our communities, and the industry if this system is adopted at scale,” Flaherty said. “It could really be a game changer.”

Ray believes other dairies, like his, will sign on in time: “We might be 10 or 15 years ahead of seeing the true benefits of a system like this, but when the droughts become longer, and our water supply becomes even tighter, we need to find a way to get ‘more crop per drop’ and protect our environment at the same time for future generations.”


Sandra Postel is director of the Global Water Policy Project, co-creator of Change the Course, and author of the forthcoming book Replenish: The Virtuous Cycle of Water and Prosperity.

About National Geographic Society

The National Geographic Society is a global nonprofit organization that uses the power of science, exploration, education and storytelling to illuminate and protect the wonder of our world. Since 1888, National Geographic has pushed the boundaries of exploration, investing in bold people and transformative ideas, providing more than 14,000 grants for work across all seven continents, reaching 3 million students each year through education offerings, and engaging audiences around the globe through signature experiences, stories and content. To learn more, visit or follow us on Instagram, Twitter and Facebook.

Meet the Author

Sandra Postel
Sandra Postel is director of the Global Water Policy Project and author of Replenish: The Virtuous Cycle of Water and Prosperity. From 2009-2015, she served as Freshwater Fellow of the National Geographic Society. Sandra is also co-creator of Change the Course, the national water stewardship initiative awarded the 2017 US Water Prize for restoring billions of gallons of water to depleted rivers and wetlands. The recipient of several honorary degrees, she works to bridge science, policy, and practice to promote innovative ways of securing water to meet both human and ecosystem needs.