Careful fertilizing protects drinking water, say experts at Modesto conference

10/29/2013 7:20 PM

05/02/2014 3:52 PM

The fertilizers that help California produce food for the world might also threaten some of the drinking water at home, experts said Tuesday in Modesto. They also noted ways that farmers have improved their use of fertilizers in recent years in response to the concerns, mainly about nitrates in public wells.

The discussion came at the 21st annual conference for the state’s Fertilizer Research and Education Program, which promotes farming practices that help ensure bountiful crops while protecting streams and aquifers.

“We have to abide by the commitment to provide a safe drinking water supply for all Californians,” said Dorene D’Adamo of Turlock, who helps to enforce the rules as a member of the State Water Resources Control Board.

Nearly 300 academics, certified crop advisers and other people turned out at the DoubleTree Hotel for the two-day conference, which concludes today. It is sponsored by the Western Plant Health Association, an industry group based in Sacramento, and the California Department of Food and Agriculture.

The nitrate issue has had plenty of attention since the release last year of a report on tainted wells in the Tulare Lake Basin, located in the southwest part of the San Joaquin Valley, and the Salinas Valley. The report, from the University of California, Davis, said the vast majority of the contamination was from cropland.

Nitrates, which come from nitrogen-based fertilizers and other sources, have been linked to thyroid cancer, birth defects and other problems. The concern is especially great for farmworkers and other low-income residents who rely on rural water systems supplied by wells.

Food and Agriculture Secretary Karen Ross said another report soon will be released by a task force charged with developing a tracking and reporting system for nitrates in high-risk areas.

The upcoming work also includes assessing nitrates in areas beyond the Tulare Lake Basin and Salinas Valley, said D’Adamo, who has worked for three Valley congressmen and served on the California Air Resources Board.

Fertilizers are simple in concept: As plants grow, they draw from the soil nitrogen, phosphorous, potassium and other nutrients, which have to be replaced for future crops.

Farmers long have used livestock manure, crop residues and other nearby sources to replenish the nutrients. Some crops, such as alfalfa and beans, have bacteria on their roots that turn airborne nitrogen into a form that enriches the soil.

The emergence in the 1940s of synthetic fertilizers, notably nitrogen from natural gas, transformed agriculture. These products, often shipped from distant places, were credited with greatly increasing crop yields.

The concerns about nitrates and other pollutants have prompted experts to call for careful use of fertilizers: Farmers should test the soil or plant tissue to see if they really are short of nutrients. They should spread the products only at the times of year when they would benefit the crops. They should irrigate in a way that keeps the fertilizers from leaching past the root zone and into aquifers.

“That’s the best thing we can do with it – keep it right there, use it over and over again,” said Doug Parker, director of the California Institute for Water Resources at UC Davis. He added that reducing fertilizer use saves farmers money.

The nitrate issue also is being addressed by regional coalitions of farmers, who are paying for water testing and prevention measures as an alternative to direct regulation by the state.

D’Adamo said the nitrate effort was prompted in part by a 2011 state law that declared drinking water to be a “human right.” She noted the irony of rural residents paying their water bills, only to be forced to buy bottled water because the public supply is polluted.

“Those individuals are having to do the unthinkable in this day and age, and that is paying for water twice in order to get safe drinking water,” she said.

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