The Elkhorn Slough is one of the areas Marc Los Huertos monitors. Photo: Paul Zaretsky
November 29, 2004
UCSC scientist endorses nitrogen management
By Jennifer McNulty
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 UCSCs 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 its 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
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
were 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
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
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
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
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 farms 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, theyll get
their money back. No one has made a withdrawal, noted Los Huertos.
Farmers are afraid to cut back on fertilizer because
theyre 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
theyre seeing that its OK. They realize excess fertilizer
hasnt 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
Return to Front Page