California farm communities pay price for decades of fertilizer use

California farm communities pay price for decades of fertilizer use

A pollutant that has leached into California aquifers since farmers first began using synthetic fertilizer continues to accumulate and would not be removed from groundwater even if the state’s agriculture businesses abruptly quit using nitrogen-based materials to boost the productivity of their crops.

That’s one of the themes of a new study from the UC Davis Agriculture Sustainability Institute that assesses the scale and sources of a kind of pollution that can harm infants if it seeps into groundwater and contributes to respiratory problems if it drifts into the air as a gas.

The report is the widest look yet at pollution from nitrogen, a common contaminant that the State Water Quality Control Board has tried in fits and starts to remove from Central Valley agricultural communities over the past decade.

The report’s authors offer a range of solutions – from creating a cap-and-trade-style market for nitrogen emissions to encouraging better waste-management practices on farms – but they concede that it could take decades to clean up groundwater that has collected fertilizer runoff since the 1940s.

“We don’t have enough technology on the shelf to be able to address the issue now,” said sustainability institute director Tom Tomich, who led the study. “There’s a need for collaboration with farmers and ranchers to develop solutions to these challenges.”

His team took seven years to weave together a broad picture of nitrogen pollution up and down the state. Past efforts have focused on specific regions, such as a 2012 study that showed up to 250,000 people are highly vulnerable to nitrogen contamination in the Salinas and southern San Joaquin valleys.

Tomich’s study found that California generates about 1.8 million tons of nitrogen every year. More than half of it comes from agricultural sources, which rely on nitrogen as a key component in fertilizers.

Of that, about 419,000 tons leach into groundwater, where it becomes a salt known as nitrate.