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Using Electromagnetic Induction to Trace
Soil Nitrogen By David Elstein
September 16, 2004
Nitrogen, a chemical nutrient needed by many growing crops, can
accidentally end up in surface or subsurface water. Now an
Agricultural Research Service scientist
is using electromagnetic induction (EI) to measure changes in the soil's
electrical conductivity, a quality that can provide important clues to the
amount of nutrients present in the soil.
Roger A. Eigenberg is an agricultural engineer at the ARS
Roman L. Hruska U.S. Meat Animal Research
Center in Clay Center, Neb. He has used EI to study several fields and
create a map with light-shaded areas representing high electrical
conductivity--or areas of high nitrate concentration--and dark areas that
indicate low conductivity, or low nitrate concentration.
Eigenberg has compared fields with and without a winter cover
crop and fields with added manure or compost. He discovered that EI could be
used to monitor the effects of winter cover crops, because EI changes
corresponded to soil nutrient changes as the cover crop took up nutrients in
the fall and released them back to the soil in the spring.
Another Clay Center research location was a former manure
compost site. In the past, scientists had to take numerous soil samples to
determine where manure rows had been located. Using the commercially available
EI equipment, Eigenberg was able to locate them in a fraction of the time. He
tracked nutrient movement over a four-year period and found that using
equipment such as the EI meter can determine nutrient buildup and movement to
help prevent nitrate leaching into groundwater.
details about this research are published in the September 2004 issue of
Agricultural Research magazine.
ARS is the U.S. Department of
Agriculture's chief scientific research agency.