The most widespread pollutants in California drinking water are nitrates -- colorless, odorless contaminants that can be especially dangerous to pregnant women and infants. One of the main sources of nitrates in California is fertilizer from farms.
The California Report Special Coverage
For decades, nitrogen fertilizer was hailed as something of a miracle product. It boosted blooms on flowering plants, beefed up tomatoes and helped trees bear fruit.
But scientists have discovered that, in some cases, only half of the nitrogen in fertilizer gets sucked up by the roots of a plant. The rest can evaporate away, or leach down below the roots, where it can make its way into the groundwater. Nitrates from fertilizer applied to fields decades ago are only now reaching some of the wells that supply cities and rural areas.
HOW MUCH IS TOO MUCH?
In the Salinas Valley, farmers grow most of the nation's lettuce. This region also has some of the worst nitrate groundwater pollution in the state.
University of California farm advisor Michael Cahn trains lettuce growers to test their fields for nitrates. By putting a thimbleful of dirt into a test tube with some water and watching as a strip changes color, farmers can assess how much nitrogen is in the soil, and calculate how much more fertilizer they really need to add.
"The way we sell this test to growers is: Hey, this is dollars that you are leaching out of your field," says Cahn.
Cahn's research on the Central Coast has shown that if farmers use less fertilizer and less water, they can still get similar lettuce yields.
One grower using the quick nitrate test is Christensen and Giannini, one of the nation's largest lettuce farms.
Today, the company is using half as much fertilizer on its lettuce. They're doing this voluntarily. In fact, there are no regulations limiting how much synthetic fertilizer a California farmer can apply to a field. And farmers aren't sanctioned if nearby wells are contaminated with high levels of nitrates.
WHO'S RESPONSIBLE?
The kind of practices they're trying on this farm could become a requirement for doing business on California's central coast. Under new rules that the regional water quality board is considering, farmers could be required to file plans and face inspections to demonstrate they're trying to protect groundwater from nitrate contamination.
Jennifer Skidgel-Clarke, head of environmental operations at Christensen and Giannini, says most growers want to be good stewards of the land. In fact, the well at her own house is contaminated with nitrates. But she doesn't think more regulation is the answer:
"Sometimes regulation can really tie a grower's hands behind their back and make it hard for them to implement things that can really work. You know, the more money we spend paying for permits, the less money we have to invest on the farm," explains Skidgel-Clarke.
Susana De Anda, co-director of the Community Water Center in Tulare County, advocates for low-income residents whose drinking water is contaminated with nitrates. She says the polluter needs to pay, and thinks farmers should be required to install monitoring wells to check for contamination.
"It shouldn't be the responsibility of the neighboring community to have to figure out how to bring in treatment because their water has been polluted by a person next door," says De Anda.
State regulators say installing monitoring wells on every farm would be cost-prohibitive and impractical, because nitrates can flow a long distance underground.
Darrin Polhemus is in charge of water quality at the State Water Resources Control Board. He says, "We certainly don't approach it from the standpoint we do like a chemical and contamination where we're trying and find who released it, make them clean it up, and penalize them for that. Nitrates are just too much everywhere, you'd spend too much time trying to track them down, and it wouldn't make sense to go after it that way."
Polhemus says a better solution is to develop a system to help educate farmers about proper use of fertilizer and test groundwater at a regional level.
Rather than taking statewide action, regulators are leaving it to the regional water boards to come up with plans to protect groundwater from farms, taking into consideration local soil conditions, rainfall, and crops. That process is just starting in regions like the Central Coast and the Central Valley.
For Californians whose drinking water is already contaminated with nitrates, the larger question remains: Who will pay to clean it up?
