Thought this CALS press release might interest some of you. I'm not
sure what that second-to-last sentence means/implies, but
Agricultural and Consumer Press Service
College of Agricultural and Life Sciences
440 Henry Mall
Research Division/University of Wisconsin-Madison
Madison WI 53706 (608) 262-1461
For Immediate Release
For More Information:
Phil Barak (608) 263-5450
ACID LINKED TO SOIL AGING
Thirty-seven years of data collected from a plot at the University of
Wisconsin-Madison's Arlington agricultural research station is
yielding alarming results: acidification from excess fertilizer is
wearing out the soil.
Phillip Barak, UW-Madison associate professor of soil chemistry and
plant nutrition, said he is part of a team carrying on research that
started in 1962. Barak and his colleagues have found the cation
exchange capacity, or the soil's ability to hold onto small bits of
calcium, magnesium and potassium, decreases because of soil acidity.
"This change is irreversible," he said.
According to Fred Madison, UW soil science professor, this is
important news for farmers. "Now you've got a whole path of
destruction," he said. Producers may have overlooked the danger that
excess nitrogen poses to groundwater, but evidence that it may also
permanently damage the soil is beginning to garner attention,
Barak said health experts have long known the role that nitrogen
plays in blue baby syndrome, a condition in which high levels of
nitrogen inhibit the blood's ability to transport oxygen. Barak said
soil becomes more acidic when nitrogen sources, whether from urea,
legume plowdown - such as alfalfa and red clover - or commercial
fertilizer are not completely used up by the crop.
This excess nitrogen becomes nitric acid, which destroys the soil's
vital ability to retain the calcium, magnesium and potassium
necessary for crop growth. Instead, these nutrients leach out of the
soil and into the groundwater. Although they are harmless, they do
cost money to replace - a price that Barak estimates at 20 percent of
what farmers normally spend on nitrogen fertilizers.
According to Barak, the United States has a 50 percent applied
nitrogen efficiency rate. This means only half of the nitrogen
applied by farmers is actually taken up by the plants, leaving the
other half to become nitric acid, he said. "That's like a tanker
truck of nitric acid being dumped on a field," Barak said.
These tons of unneutralized nitric acid age the soil very quickly,
according to Barak. He said the soil at his Arlington test site has,
in 30 years of "normal" agricultural acid inputs, aged the equivalent
of 5,000 years with natural source acid inputs.
Barak said the aging is remarkable considering the age of the soils.
"Keep in mind these soils have only been in existence for 10,000
years," he said.
Barak said the fine soils of Wisconsin are "tender," and the very
qualities that make them fertile also make them vulnerable. They are
easily dissolved by acidity, he said. According to Barak, if excess
nitrogen inputs continue, unneutralized, northern soils might soon
become like the sandy, less productive soils of the southeast region
of the United States.
"With the long term, over-application of nitrogen, we run the risk of
irreparably damaging the soil," Madison said.
But Barak said the news is not all bad. He cited two ways farmers
can better care for their valuable soil. The first, and preventative,
measure is to use nitrogen more efficiently. Producers should account
for all sources of nitrogen, and adjust their commercial inputs
accordingly. Excess nitrogen not only acidifies, it can leach into
groundwater or run off into surface water.
The second, and remedial, measure is applying agricultural lime.
Liming can neutralize the damaging acid and protect the fields.
"Agliming has been known for 3,000 years," Barak said. "Use it. It's
like TUMS for the soil." By closely monitoring pH levels and
appropriately applying agricultural lime, farmers can greatly retard
what Barak refers to as "accelerated soil weathering."
Since 1950, Barak reports that nitrogen use, as well as agricultural
production, has skyrocketed. The United States is locked into a
system of high production that cannot be reversed without serious
negative implications, he said. The result is that farmers must
learn to be more attentive to their treatment of the soil.
Writer: Andy Napgezek, 836-6651
This story first appeared in the March 3, 1999 issue of the Badger
Herald, an independent student newspaper at the University of
Michele Gale-Sinex, communications manager
Center for Integrated Ag Systems
UW-Madison College of Ag and Life Sciences
Voice: (608) 262-8018 FAX: (608) 265-3020
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