Long-Term Experiments Key to Understanding
By Kathryn Barry
October 30, 1998
Long-term experiments in farmland ecosystems may be the only means for
measuring the sustainability of agriculture over time and may help predict
future global change, U.S. Department of
Agriculture soil scientist Paul Rasmussen says in today's issue of Science.
Rasmussen helps coordinate ongoing experiments set up in 1931 at a research
station in Pendleton, Ore. USDA's Agricultural Research Service and
Oregon State University manage the station.
ARS is the chief research agency of USDA.
Though one of the oldest projects in the western U.S., the Pendleton
experiments are young compared to those started in the 1800s in Rothamsted,
England, and Sanborn, Mo.
The key for the future, said Rasmussen, will be to identify and support
long-term experiments that have been managed properly. "Most of those
existing today have survived war, drought, politics and internal turmoil,"
he said. "Commitment is needed to ensure the continuance of those with
relevance and merit."
Long-term experiments were established to define the immediate effects of
crop management on yield and soil quality. They have shown that leaving crop
residue--stalks and other unused plant material--on the field instead of
plowing it under can be beneficial. In this system, seeds are then sown into
the soil through the residue.
"While organic matter rebuilds slowly over decades, water infiltration
and earthworm activity increase markedly in just a few years," said
The experiments are also providing an increasing number of unforeseen
benefits, he said. For example, soil samples have been collected and archived
at Rothamsted since 1843. Now, scientists can analyze these samples to
determine how the levels of potentially toxic elements--such as cadmium and
certain dioxins--have been changing in the soil.
At the Sanborn site, other researchers discovered a soil organism that led
to development of the antibiotic Aureomycin.
The biggest benefits may be yet to come. NATO's Global Change and
Terrestrial Ecosystem project is collecting data from long-term
experiments--including those in Oregon, England and Missouri--to determine
whether existing computer models can accurately predict effects of global
Long-term plots in the U.S. also play a role in ARS' ongoing effort to
understand how the soil may mitigate global change by sequestering carbon.
Currently, there is twice as much carbon in soil as in atmospheric
"Models are only as good as the data on which they are based,"
said Rasmussen. When an ecosystem is disturbed, he said, it can take 10 to 40
years to reach a new equilibrium. "Conclusions based on a 10-year segment
of data may be very different than those based on 50 or more years of
data," he said.
Scientific contact: Paul Rasmussen, soil scientist,
Columbia Plateau Conservation Research
Center, Agricultural Research Service, USDA, Pendleton, OR 97801-0370,
(541) 278-4415, fax (541) 278-4372, email@example.com.