Nitrogen pollution

The Elkhorn Slough is one of the areas Marc Los Huertos monitors. Photo: Paul Zaretsky

November 29, 2004

UCSC scientist endorses nitrogen management efforts

As a soil scientist at UCSC, Marc Los Huertos helps farmers on the Central Coast manage nitrogen levels to maximize harvests and minimize pollution.

Los Huertos is also part of a growing global effort to address the problem of farm-generated nitrogen pollution. Just back from the Third International Nitrogen Conference in Nanjing, China, Los Huertos has a sobering message for farmers:

“China is ramping up agricultural production, and strong international environmental regulations could be what saves U.S. farming from a formidable competitor,” said Los Huertos, who manages research for UCSC’s Center for Agroecology & Sustainable Food Systems (CASFS).

“I saw hundreds of miles of greenhouses,” Los Huertos said of a three-week tour of the Chinese countryside that followed the Nanjing conference. “Their fertility is terribly managed, but it’s cheap. If they can figure out how to get their produce here fast enough, the Chinese could outcompete U.S. farmers in no time at all.”

Convinced that U.S. farmers have a huge stake in regulations that would force global competitors to clean up their act, too, Los Huertos is eager to increase public understanding of agriculture-related nitrogen pollution.

“My job is to prepare farmers for policies that might affect them, whether at the state, federal, or international level, so I went to China to get a sense of the international movement,” said Los Huertos.

Nitrogen accumulation reduces biodiversity, acidifies soil and water, degrades coastal environments, reduces forest productivity, contributes to the greenhouse effect, and depletes the ozone. “Reactive nitrogen is so high in the developed world that we’re polluting ourselves out of clean air, drinking water, and biodiversity,” he said.

Although essential to life, nitrogen must be converted from a gas to a reactive form to be usable by most organisms, including plants. The accumulation of reactive nitrogen in the environment is largely a result of the conversion of enormous quantities of nitrogen into fertilizers that are used in the production of food and fiber. Reactive nitrogen is also a by-product of fossil fuel combustion for transportation and energy production.

A significant portion of nitrogen in fertilizer is never taken up by plants and instead runs off, contributing to the “cascade” of atmospheric and aquatic nitrogen accumulating in many regions of the world--even as most of Africa and parts of South America and Asia suffer from a deficiency of reactive nitrogen in the soil.

In Nanjing, about 800 conference participants approved the “Nanjing Declaration on Nitrogen Management,” which urges the United Nations Environment Program to promote understanding of the nitrogen cycle, assess consequences of its disturbance, provide policy advice and early-warning information, and promote international cooperation.

With CASFS Director Carol Shennan, a professor of environmental studies at UCSC, Los Huertos monitors nitrogen in several important waterways along the Central Coast, including the Pajaro River and around the Elkhorn Slough, one of the largest remaining tidal wetlands in California. Nitrogen levels in Central Coast agricultural watersheds have steadily increased since the 1950s, when levels of <1 ppm were typical, according to state records compiled by Los Huertos. Today, Los Huertos regularly documents levels of 10 ppm in May and 20 ppm in the fall in the Pajaro River. Drinking water standards allow for a maximum of 10 ppm.

Unlike some coastal areas where fertilizer runoff has wiped out marine life, Monterey Bay circulates the ocean water and flushes nutrients through the ecosystem. This mixing and upwelling makes it difficult for scientists to assess how nitrogen runoff affects the bay, but it certainly has a role in the freshwater streams, according to Los Huertos.

“We know we have excess nitrogen on the Central Coast, and farmers and the state and federal government are struggling with finding ways to control polluted runoff,” said Los Huertos.

In other coastal areas, runoff from nitrate-based fertilizers has had devastating consequences. In the Gulf of Mexico, a 5,000-square-mile area from the mouth of the Mississippi River almost to the Texas border is overrun with nitrates each summer, triggering an algae bloom that severely reduces oxygen levels until late September.

Researchers, including Los Huertos, have been working with government regulators to address the problem. The debate centers on whether to take a “carrot or stick” approach, observed Los Huertos.

California is considering a permit-like approach that would encourage farmers to take “short courses” to learn about nitrogen pollution, to adopt a water-quality protection plan, or to monitor their farm’s discharge--or pay someone else to monitor it.

Los Huertos described two intriguing programs he learned about at the Nanjing conference. A program run by American Farmland Trust in the corn belt rewards farmers who reduce their use of fertilizer by allowing them to bank the financial savings with a guarantee that if their yields drop, they’ll get their money back. No one has made a withdrawal, noted Los Huertos.

“Farmers are afraid to cut back on fertilizer because they’re afraid their harvests will drop, but some of what they apply ends up in our waterways,” he said. “This program gives farmers a low-risk incentive to cut back, and they’re seeing that it’s OK. They realize excess fertilizer hasn’t benefited their crops. They might as well have been pouring that money down the drain.”

A more punitive program run by the Nebraska Resource Conservation District fines farmers who overfertilize and contaminate wells to the point that the water becomes undrinkable.

“Farming is a ruthless business, and you have to be smart to make it,” noted Los Huertos. “Margins are tight, and the risks are high, but the most successful growers are innovators. We have to find ways to ease the transition for growers who have become accustomed to using fertilizer in excess of crop needs. And we need to find ways to reduce the amount of nitrate that reaches sensitive habitats and sources of drinking water.”

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