Solving the problem of nitrate contamination
- May 15, 2010
Farmers and state officials are exploring solutions to nitrate leaching in heavily affected parts of the state, including solutions that go beyond paying millions of dollars for a treatment plant. But some proposals are more controversial than others.
Experts say any serious action on dealing with nitrates has to begin with regulating farmers who rely on commercial fertilizer, the leading cause of nitrate leaching in California.
"The largest problem is irrigated agriculture. It covers a much larger area, it's a constant input of nitrates in groundwater and you have constant irrigation and over-irrigation, which drives the nitrates deeper into the groundwater," said Jean Moran, professor of earth and environmental science at 麻豆传媒社区入口, East Bay and a former research scientist at Lawrence Livermore National Laboratory. "But if you look for new evidence of regulations on nitrate issues in groundwater, you just don't find them."
That could be changing in the Central Valley, where regulators are working on a set of rules to govern fertilizer use on fields for the first time.
One option would require farmers to install mandatory groundwater-monitoring wells on each farm and report back to the state — a controversial idea that even regulators admit is unlikely to take root.
Growers say that they would prefer to employ voluntary measures to prevent pollution to the extent they can, and they have told the Central Valley Regional Water Quality Control Board they should not be required to comply with statewide water-quality limits.
Renee Pinel feels the same way. As CEO of the Western Plant Health Association, a nonprofit trade association that represents agricultural retailers and fertilizer manufacturers, she believes the state should not be regulating farmers at all.
"Monitoring wells are expensive, and individual growers should not take on that expense if there is no demonstrated proof that whatever may be tested has anything to do with [them]," Pinel said. "We would be concerned about the finger of blame being pointed at one sector just because it's easy."
The State Water Resources Control Board has taken important steps toward understanding groundwater problems in recent years, funding a series of studies by the U.S. Geological Survey to measure nitrates in groundwater across the state. Much of that information is available in a new, searchable mapping database, called GeoTracker, on the state water board website.
In 2007, the state appropriated $2 million for a study to assess the feasibility of helping disadvantaged communities get access to safe drinking water in the southern Central Valley and the Salinas Valley — two of the most nitrate-saturated parts of California. Another set of recommendations will focus on developing a cleanup plan for both regions. Money for the project was set aside in Proposition 84, the Safe Drinking Water, Water Quality and Supply, Flood Control, River and Coastal Protection Bond Act of 2006. Unfortunately, a freeze on Proposition 84 bond funding means the project has yet to begin.
The Central Valley Water Board also helped create the Central Valley Salinity Coalition, or CV-SALTS, a project to identify the main sources of salt and nitrate problems. The group is taking a long-term view, working on cleanup and reduction plans over the next 100 years.
Practical solutions
One way to stop the nitrate cycle is to use less fertilizer. Depending on the type of crop and soil conditions, some plants only use half of the fertilizer a farmer applies — leaving the rest to evaporate or percolate into the groundwater.
Farmers have little incentive to use less commercial fertilizer, as long as it remains an affordable commodity, say experts. And in California, new housing developments are being built on land previously reserved for farming — putting pressure on farmers to produce more on less land. Commercial fertilizer use increased almost ninefold on American farms between 1940 and 1972 before leveling off in the 1980s, while a highly mechanized, nitrogen-intensive model of farming pushed crop yields through the roof.
A small group of lettuce farmers in Monterey County has discovered it's possible to save money on fertilizer, cut back on water and reduce nitrates without sacrificing crop yield.
Using a "quick nitrate" test, provided by the University of California Cooperative Extension, growers can gauge how many nitrates are already in the soil and use only as much fertilizer as their lettuce needs to grow. Michael Cahn, a UC Cooperative farm adviser, says he helped one company use 70 pounds less fertilizer per acre and got the same yield. Another benefit? Less water needed to grow the lettuce.
The test is both affordable and widely available but isn't popular, according to Cahn.
"The test is cheap, but you still have to go into the field and do it — so it costs the company labor. We figure it's still not cheaper than buying more fertilizer. Water's cheap too. These crops don't suffer by having extra nitrogen and extra water."
Fertilizer and irrigation go hand in hand, and conserving irrigation water cuts down on fertilizer use as well. The Pacific Institute, an Oakland-based think tank, estimates that farmers could save at least 17 percent more water if they installed water-efficient sprinklers and precision irrigation systems.
Many farmers have already made the switch, but progress has been slow. Nearly 60 percent of crops in California are still flood-irrigated, including more than 80 percent of field crops, according to a state report from 2001 (the most recent numbers available).