November 26,
2004, ARS News Service: An organic crop rotation
is at least as sustainable as no-till farming or chisel
tillage in terms of nitrogen loss and corn yields, according
to an Agricultural Research Service (ARS) study. The
five-year study showed that a three-year rotation of
organic corn, soybeans, wheat and a legume cover crop
had nitrogen losses and corn yields similar to those
on land where either chisel-tillage or no-till farming
had been used.
The organic rotation relied on poultry litter, soybeans
and a hairy vetch legume cover crop as nitrogen sources.
The study showed the highest risk of leaching nitrogen
to groundwater was on fields with no-till or chisel
tillage where both commercial fertilizer and poultry
litter had been used. Future studies are planned to
measure or estimate leaching losses.
Michel Cavigelli, an ARS soil scientist at the Henry
A. Wallace Beltsville (Md.) Agricultural Research Center,
and Steve Green, an ARS soil scientist research associate,
are studying nitrogen losses with organic and other
farming systems. The study is part of a farming systems
project begun in 1996 to compare the sustainability
of organic and conventional farming. Minimizing losses
of nitrogen and other nutrients is a key element of
both environmental and economic sustainability.
Cavigelli and Green used measurements and estimates
to get an initial picture of nitrogen inputs and losses.
They are conducting additional studies to improve their
ability to more accurately estimate the amount of nitrogen
added naturally by soybean plants.
The scientists got their poultry litter--both composted
and noncomposted--from commercial farms on Maryland's
Eastern Shore. They studied corn-soybean rotations,
mostly with winter wheat, using various levels of tillage.
Green presented this research at the American Society
of Agronomy's recent annual meeting in Seattle, Wash.,
along with a report on the risk of phosphorus loss from
erosion. He found the risk of losing phosphorus from
soil erosion was similar for both the organic system
and land that was chisel-plowed, but the risk was lower
with a conventional no-till system.
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