MODESTO -- Experts in fertilizing crops said Tuesday that the industry has done much to clean up its practices but could do more.
About 250 people attending a conference at Modesto Centre Plaza heard about efforts to apply fertilizer with increased precision, saving money for farmers and reducing pollution.
"We need to let people know that this is something the industry is supporting, that we are behind good nutrient management," said Robert Mikkelsen of Merced, director for western North America at the International Plant Nutrition Institute.
Fertilizer suppliers, users, researchers and regulators came from around the state for the 20th annual conference, which ends today. It was put on by the Western Plant Health Association, an industry group based in Sacramento, and the California Department of Food and Agriculture.
Karen Ross, food and agriculture secretary for Gov. Jerry Brown, said the issue is not simple in a state with about 400 farm products.
"So many people fail to understand the complexity of plant nutrient management, and what works for almonds does not work for strawberries," she said.
Fertilizer is as crucial to farming as water, sunlight and pest control. Farmers have to replace the nitrogen, potassium and other soil nutrients that are taken up by their crops.
Some methods are centuries old: Farmers can use manure from livestock, including the Modesto area's many dairy cows, to enrich the ground for feed crops. They can plant beans or other crops that capture airborne nitrogen and make it available to plant roots. And they can make compost from crop residue and other sources.
Since the 1940s, farmers have made substantial use of synthetic fertilizers, chiefly nitrogen extracted from natural gas.
State and federal regulators are watching, because excessive fertilizer in streams and groundwater could make people sick. Much of the recent attention has been on wells tainted by nitrates, a form of nitrogen linked to thyroid cancer, birth defects and other problems.
The vast majority of nitrates in the Tulare Lake Basin and Salinas Valley is from cropland, according to a report this year from the University of California at Davis.
Mikkelsen said some people might disagree about agriculture's contribution, "but whatever it is, it's a lot, and we need to do something different."
He said farmers should apply a fertilizer at the right rate, at the right time of year and in a way that best gets the nutrients into the crops. Grapes, for example, benefit most from nitrogen when the fruit is starting to form, he said.
"If you miss that two- or three-week period, it really hurts your crop," he said.
He and other experts cited the increasing use of "fertigation," which involves delivering nutrients via drip irrigation or small sprinklers. This reduces the chances of the substances leaching into groundwater, they said.
Experts told of how farmers can determine the need for fertilizer by testing the soil or plant tissue. This allows them to move away from fertilizing at a constant rate no matter the conditions.
"Today, those practices are not occurring," said Michael Johnson, who oversees a farmer-funded water monitoring program in part of the San Joaquin Valley. "The cost of nitrogen fertilizer, for example, is so high that you can't afford to overapply."
Bee staff writer John Holland can be reached at firstname.lastname@example.org or (209) 578-2385.