Madison, Wisconsin
May 27, 2008
Scientists compare organic and
conventional grain yields and address production challenges in
organic cropping systems
While demand for organic meat and milk is increasing by about
20% per year in the United States, almost all organic grain and
forage to support these industries in the mid-Atlantic region is
imported from other regions. To meet this demand locally, area
farmers need information on expected crop yields and effective
management options.
Scientists in the Sustainable Agricultural Systems Laboratory at
the USDA-Agricultural Research Service (ARS) Beltsville
Agricultural Research Center (BARC) in Maryland have studied the
impact of diverse organic cropping systems on crop yields over a
ten year period. Results from the study, which was funded by
USDA-ARS, were published in the May-June issue of Agronomy
Journal.
The researchers collected data on crop yields, nitrogen inputs,
weed densities, and crop populations from the USDA-ARS
Beltsville Farming Systems Project (FSP), a long-term cropping
systems trial with two conventional and three organic systems
that was established in 1996. The three organic systems differed
in crop rotation length and complexity.
The study revealed that corn and soybean yields in organic
systems were, on average, 76 and 82%, respectively, of those in
conventional systems in years with normal weather. Winter wheat
yields were similar among systems. Corn yields were lower in the
organic than in the conventional systems primarily due to lower
nitrogen availability in the organic systems, which rely on
legume crops and animal manures. Weed competition also
contributed to lower corn grain yields in organic systems. For
soybean, weed competition alone accounted for differences in
yield between organic and conventional systems.
Among organic systems crop rotation length and complexity had a
strong impact on corn grain yield. A crop rotation that included
corn, soybean, wheat and hay resulted in average corn grain
yield 30% greater than in a simple corn-soybean rotation and 10%
greater than in a corn-soybean-wheat rotation. Differences were
due to increased nitrogen availability and lowered weed
competition with increasing crop rotation length and complexity.
Crop rotation length and complexity did not affect soybean and
wheat yields.
Dr. Michel Cavigelli, lead author of the study, stated, “These
research results show that longer, more complex crop rotations
can help address the two most important production challenges in
organic grain crop production: providing adequate nitrogen for
crop needs and decreasing weed competition.” This research
should help organic farmers and those considering transitioning
to organic farming select crop rotations best suited for the
mid-Atlantic region. Since the FSP is one of only a handful of
long-term cropping systems trials that includes diverse organic
crop rotations, these results will also be of interest to
organic farmers and those working with organic farmers
nationwide.
Ongoing research at the USDA-ARS Sustainable Agricultural
Systems Lab at BARC is designed to increase soil nitrogen
availability and decrease weed pressure in organic grain crop
rotations.
The full article is available for no charge for 30 days
following the date of this summary. View the abstract at
http://agron.scijournals.org/cgi/content/abstract/100/3/785.
A peer-reviewed international journal of agriculture and
natural resource sciences, Agronomy Journal is published six
times a year by the American Society of Agronomy, with articles
relating to original research in soil science, crop science,
agroclimatology and agronomic modeling, production agriculture,
and software. For more information visit:
http://agron.scijournals.org.
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Agronomy (ASA) is a scientific society helping its 8,000+
members advance the disciplines and practices of agronomy by
supporting professional growth and science policy initiatives,
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