Federal agents this week searched a major producer of fertilizer for California's organic farmers, widening concern about the use of synthetic chemicals in the industry.

The raid Thursday targeted Port Organic Products Ltd. of Bakersfield. Industry sources estimate the company produced up to half of the liquid fertilizer used on the state's organic farms in recent years.

The Bee reported in December on a state investigation that caught another large organic fertilizer maker spiking its product with synthetic nitrogen, which is cheap, difficult to detect – and banned from organic farms.

Since then, the organic industry and state officials have taken several steps to catch violators in California, which produces nearly 60 percent of the U.S. harvest of organic fruits, nuts and vegetables.

California Certified Organic Farmers, the state's top organic certifier, last week mandated inspections of fertilizer makers that sell to its clients. Meanwhile, Earthbound Farm, the nation's largest producer of organic greens, is stepping up a new testing program for the chemicals its farmers use. In addition, state fertilizer inspectors may get additional auditing powers and the state Senate Food and Agriculture Committee has scheduled a hearing on the issue Feb. 3.

As Thursday's raid indicates, work remains to improve a patchwork regulatory system that presumes manufacturers tell the truth about their products. On Thursday at the Eco-Farm Conference in Monterey, frustrated farmers and fertilizer makers alike called for stronger oversight.

"Trust is fine until there's money on the table," said Dennis Macura, who runs the Morgan Hill-based fertilizer company AgroThrive.

No charges have been filed in the most recent case, but Kern County records dating back to 2005 show Port Organic has stocked thousands of gallons of aqua ammonia, a common source of synthetic nitrogen.

The company's fertilizers were ostensibly made from ground-up fish carcasses. But documents obtained by The Bee show that California Department of Food and Agriculture officials suspected the company of using synthetic nitrogen back in October 2007.

Port Organic's president, Ken Nelson, did not return calls from The Bee. On Friday, California Certified Organic Farmers ordered its clients to stop using Port Organic's products.

"We are shocked at the lack of integrity of this manufacturer … and we are doing our best to restore trust in the organic system," said Claudia Reid, the group's policy director.

Synthetic fertilizers don't present food safety risks, but the organic movement opposes them because they take a great deal of energy to produce, decrease natural soil fertility and threaten water quality.

The incentive to make a fake organic fertilizer is clear, since synthetic nitrogen is as much as 20 times cheaper than approved nutrient sources such as ground-up fish and chicken feathers. Synthetic nitrogen often works better than organic products and it also is difficult to detect using standard laboratory analyses.

Port Organic is the latest in a series of fertilizer makers to be accused of passing off chemical fertilizers as organic.

California Liquid Fertilizer held as much as a third of the state market in 2006 before state regulators quietly pulled the Salinas-area company's leading product, which had been used by Earthbound Farm and other industry leaders. Another company pulled its fertilizer from the organic market in November 2007 amid a state investigation.

As part of efforts to crack down on unscrupulous fertilizer makers, Earthbound Farm and others are experimenting with more-sophisticated analyses that help reveal whether nitrogen in a fertilizer came from a natural source.

The state Fertilizer Inspection Advisory Committee also is considering expanding inspectors' audit powers, said Nate Dechoretz, who heads the Agriculture Department's Inspection Services Division.

The Feb. 3 Senate hearing will probe the causes of the Department of Food and Agriculture's slow responses and look for legislative remedies, said Sen. Dean Florez, D-Shafter, who chairs the Food and Agriculture Committee.

"We're placing a tremendous amount of trust in the industry to police itself," Florez said. "I think that hasn't worked very well."

While the U.S. Department of Agriculture decides what materials may be used on an organic farm, state agriculture officials investigate complaints. But the review of brands of fertilizers falls mostly to the Organic Materials Review Institute, which is paid by companies to evaluate products.

The Eugene, Ore., group had evaluated Port Organic's products and listed them for use on organic farms. A spokesman for the nonprofit said in early January that the company was under investigation for possible violations.

Kern County's Environmental Health Services Department had fined Port Organic more than $18,000 for improperly storing aqua ammonia in 2005 and 2007.

According to the department's director, Matt Constantine, county officials did not bring the violations to the attention of either state agriculture officials or the Organic Materials Review Institute.

Call The Bee's Jim Downing, (916) 321-1065.