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2-Plants: New U.S. study on yield drag in RR soybeans

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TITLE:  Evidence of the Magnitude and Consequences of the Roundup
        Ready Soybean Yield Drag from University-Based Varietal
        Trials in 1998
SOURCE: Charles Benbrook; Benbrook Consulting Services;
        Sandpoint, Idaho; U.S.
        Ag BioTech InfoNet; Technical Paper Number 1
DATE:   July 13, 1999

----------------- archive: ------------------

Dear GENET-news readers,

a new study on RR soybean yield drag has been published in the
U.S.: "Evidence of the Magnitude and Consequences of the Roundup
Ready Soybean Yield Drag from University-Based Varietal Trials in
1998". You can download the pdf-file at
Attached you will find the executive summary of the study.

Hartmut Meyer

+++++     +++++

Executive Summary

Over half the soybeans planted in the United States in 1999 are
varieties genetically engineered to tolerate applications of the
broad-spectrum, contact herbicide glyphosate manufactured by
Monsanto Company (Trade Name, Roundup). Just a small fraction of
soybeans produced in 1996 were "Roundup Ready² -- varieties able
to tolerate direct applications of glyphosate herbicide. The
rapid adoption of Roundup Ready (RR) soybeans has been
unprecedented in the history of American row-crop agriculture. No
new genetic trait, nor any pesticide has so dramatically gained
market share in such a short period of time.

Roundup Ready soybeans have proven so popular with farmers
because they greatly simplify the task of managing weeds and help
farmers avoid a variety of problems associated with other
herbicide-based weed management systems. They have proven
especially popular among farmers who must complete weed
management practices on a timely basis over hundreds to thousands
of acres of soybeans. The success of RR soybeans is remarkable in
light of the magnitude of the so-called Roundup Ready "yield
drag.² Under most conditions extensive evidence shows that RR
soybeans produce lower yields than possible if farmers planted
comparable but non-engineered varieties.

This report reviews the results of over 8,200 university-based
soybean varietal trials in 1998 and reaches the following
conclusions regarding the magnitude of the RR soybean yield drag:

- The yield drag between top RR varieties compared to top
  conventional varieties averages 4.6 bushels per acre, or 6.7
- When comparing average yields across the top 5 varieties tested
  in 8 states, the yield drag averages 4.1 bushels, or 6.1
- Across all varieties tested, the yield drag averages 3.1
  bushels, or 5.3 percent.
- In some areas of the Midwest, the best conventional variety
  sold by seed companies produces yields on average 10 percent or
  more higher than comparable Roundup Ready varieties sold by the
  same seed companies.

It is important to place the RR soybean yield drag in
perspective. From 1975 to 1994 soybean yields rose on average
about 0.5 bushels per year. In 1999 the RR soybean yield drag
could result in perhaps a 2.0 to 2.5 percent reduction in
national average soybean yields, compared to what they would
likely have been if seed companies had not dramatically shifted
breeding priorities to focus on herbicide tolerance. If not
reversed by future breeding enhancements, this downward shift in
soybean yield potential could emerge as the most significant
decline in a major crop ever associated with a single genetic

On whether RR soybean systems reduce pesticide use and increase
grower profits, our analysis shows that:

- RR soybean systems are largely dependent on herbicides and
  hence are not likely to reduce herbicide use or reliance.
  Claims otherwise are based on incomplete information or
  analytically flawed comparisons that do not tell the whole
- Farmers growing RR soybeans used 2 to 5 times more herbicide
  measured in pounds applied per acre, compared to the other
  popular weed management systems used on most soybean fields not
  planted to RR varieties in 1998. RR herbicide use exceeds the
  level on many farms using multitactic Integrated Weed
  Management systems by a factor of 10 or more.
- There is clear evidence that Roundup use by farmers planting RR
  soybeans has risen markedly in 1999 because of the emergence of
  a degree of tolerance to Roundup in several key weed species,
  shifts in weeds toward those less sensitive to Roundup, price
  cuts and aggressive marketing.
- Roundup use on soybeans may well double from 1998 levels within
  the next few years. But if current trends continue in the way
  RR technology is used, the efficacy and market share of Roundup
  may then fall just as quickly.
- The RR soybean yield drag and technology fee impose a sizable
  indirect tax on the income of soybean producers, ranging from a
  few percent where RR varieties work best to over 12 percent of
  gross income per acre. The remarkable popularity of Roundup
  Ready soybeans, despite their cost and the significant yield
  drag associated with their use, is evidence of the difficulty
  and high cost of today¹s herbicide-dependent soybean weed
  management systems. The rapid evolution of weeds better able to
  withstand applications of Roundup reinforces the need for more
  integrated, multiple tactic weed management systems.

-| Hartmut Meyer
-| Co-ordinator
-| The European NGO Network on Genetic Engineering
-| Reinhaeuser Landstr. 51
-| D - 37083 Goettingen
-| Germany
-| phone: #49-551-7700027
-| fax  : #49-551-7701672
-| email:

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