Project assesses management of nitrates on farms

Issue Date: March 14, 2012
By Kate Campbell

Ahead of a new report assessing nitrate levels in groundwater, experts briefed the State Board of Food and Agriculture last week on efforts to address the issue.

The board heard from Tom Tomich, University of California Agricultural Sustainability Institute director, about the three-year California Nitrogen Assessment project. The assessment studies the nitrogen cycle and the impact of current farming practices on the movement of nitrogen-based compounds into water.

The assessment was conducted in tandem with research into nitrate levels in groundwater in the Tulare Lake Basin and the Salinas Valley. A UC report on the groundwater in these two areas, called for in 2008 legislation, was released March 13.

Tomich said the overall assessment provides the first comprehensive look at nitrogen flows throughout the state, particularly nitrogen converted to fertilizer to help increase crop yields.

He told the board that better nitrogen management may continue to provide strong yields in food production while at the same time protecting the environment, but that new policy approaches will be needed.

"It will require an integrated approach, rather than a silo approach, to policy issues," he said, referring to the technical complexities and need for involvement by a number of agencies and stakeholders.

"Because nitrogen is multi-media—it exists in the air, water, soil, food—a one-size-fits-all approach to management won't work," he said.

Scientists stress that organisms require nitrogen to produce amino acids, a basic building block of life. Nitrogen makes up 78 percent of the atmosphere, but most organisms cannot use this gaseous form. It has to be converted to fixed forms—nitrates and nitrites—through natural bacterial action or commercial production.

Opportunities to reduce problematic nitrate levels in the environment, Tomich said, may include changes to crop and manure management practices and adoption of new technologies.

"If we can improve fertilizer-use efficiency, and there are plenty of technical studies that suggest we can, that will help farmers and the environment," Tomich told the board.

Danny Merkley, California Farm Bureau Federation water resources director, noted that commercial nitrogen applications significantly increased between 1945 and the late 1980s but have leveled off since then, while crop yields have risen substantially since 1990—demonstrating improved management by farmers.

"California farmers have recognized the need to adapt and improve, without a legislative or regulatory mandate," Merkley said.

Tomich said the UC assessment indicates excess nitrogen is going into groundwater as nitrates, with relatively little moving into surface water. But this is not uniform throughout the state; Tomich said different parts of the state face greater challenges than others.

"Because nitrates going into groundwater build up over decades, even if those leakages were to be shut down tomorrow, the problem will persist for some time," he said.

The state board heard from presenters who described ways to reduce nitrates in groundwater, such as precision feeding of livestock, improved manure management and better nutrient-use efficiency in cropping.

Paul Martin of Western United Dairymen told the board the dairy sector has been working on nitrogen and nutrient issues for years. Since 1997, the California Dairy Quality Assurance Program has been providing dairy operators with tools to address nutrient management concerns and navigate the many rules and regulations that govern dairy production.

In the past several years, the state's dairy sector has invested $21 million in research and drilling on-dairy monitoring wells to determine effects of discharges on groundwater, he said.

Dairy regulations require strict accounting, Martin said, adding, "we're focused on nitrogen management, investing in new facilities, funding more research and looking for additional infrastructure improvements. And we need partners in this process, not adversaries."

Research into the benefits and use of nitrogen on almonds has provided some useful insights, according to Robert Curtis of the Almond Board of California.

For example, he said research indicates that overfertilizing doesn't improve almond yields. Many almond growers appear to realize this, he said, because leaf testing studies find nitrogen-use efficiency for tested almond orchards at nearly 80 percent utilization, among the highest utilization rate of any crop in the state.

Like many other commodity groups in California, dairy and almond organizations have established best management practices for crop production, which include nutrient and water management techniques.

Researchers at UC and other institutions have been increasing the number of projects devoted to understanding and improving nutrient management.

More than a dozen research studies are now under way, said Barbara Allen-Diaz, UC Agriculture and Natural Resources vice president, who told the board there are "a wide range of solutions available."

Allen-Diaz said university researchers are working with growers to provide options for protecting groundwater. ANR research findings and ongoing studies are available online at

For more than 20 years, an assessment charged on every California fertilizer sale has gone toward research and education on the use and handling of fertilizers. The Fertilizer Research and Education Program, operated by the state Department of Food and Agriculture, has developed best management practices for application of nitrogen products. For more information, see

The UC nitrate report, along with videos and maps, is posted at

The State Water Resources Control Board will hold a public workshop on nitrates in groundwater May 23 to consider public input on options outlined in the UC report. The report and public input will be used to develop recommendations to the Legislature later this year, as required by legislation.

(Kate Campbell is an assistant editor of Ag Alert. She may be contacted at

Permission for use is granted, however, credit must be made to the California Farm Bureau Federation when reprinting this item.