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United States Department of Agriculture

Agricultural Research Service


Long-Term Experiments Key to Understanding Farmland Ecosystems

By Kathryn Barry Stelljes
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 Rasmussen.

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 climate change.

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 CO2.

"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,

Last Modified: 5/15/2017
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