Comparing organic and conventional crops

28-03-2008 | |

Can organic cropping systems be as productive as conventional systems? The answer is an unqualified, “Yes” for alfalfa or wheat and a qualified “Yes most of the time” for corn and soybeans according to research reported by scientists at the University of Wisconsin-Madison and agricultural consulting firm AGSTAT in the March-April 2008 issue of Agronomy Journal.

The researchers primarily based their answer on results from the Wisconsin
Integrated Cropping Systems Trials, conducted for 13 years (1990-2002) at
Arlington, WI and 8 years (1990-1997) at Elkhorn, WI. These trials compared six
cropping systems (three cash grain and three forage based crops) ranging from
diverse, organic systems to less diverse, conventional systems. The cash grain
systems were 1) conventional continuous corn, 2) conventional corn-soybean, and
3) organic corn-soybean-wheat where the wheat included a leguminous cover crop.
The three forage based systems were 1) conventional
corn-alfalfa-alfalfa-alfalfa, 2) organic corn-oats-alfalfa-alfalfa, and 3)
rotationally grazed pasture.

In this research they found that: organic
forage crops yielded as much or more dry matter as their conventional
counterparts with quality sufficient to produce as much milk as the conventional
systems; and organic grain crops: corn, soybean, and winter wheat produced 90%
as well as their conventionally managed counterparts. In spite of some climatic
differences and a large difference in soil drainage between the two sites, the
relatively small difference in the way the cropping systems performed suggested
that these results are widely applicable across prairie-derived soils in the
U.S. upper Midwest.

The researchers also compared their results to other
data analysis done on this topic in the U.S. Midwest. Although researchers found
that diverse, low-input/organic cropping systems were as productive as
conventional systems most of the time, there is a need for further research,
according to the study’s author Dr. Joshua L. Posner, University of

“There continues to be improvements in weed control for
organic systems that may close the gap in productivity of corn and soybeans in
wet seasons,” Posner says. “On the other hand, technological advances may
accelerate productivity gains in conventional systems that would outstrip the
gains in organic systems even in favorable years.”

The true question of
whether organic cropping systems are as productive as conventional systems is a
dynamic question and one that requires continual reevaluation.

The full
article is available for no charge for 30 days following the date of this
summary. View the abstract here.  

American Society of Agronomy (ASA)

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