>Does anyone know if the yield of GM corn and soybeans are different or the
>same as conventionally bred corn and soybeans. There must be information
>on that somewhere and I thought some one on the list would know where it is.
>
>Thanks,
>
>Bill Liebhardt
Bill,
This is from the document GE Debate I am compiling, which lists the
various pro and con arguments.
4.1. CLAIM: GE-CROPS WILL INCREASE YIELDS
- On the whole, GE crops do not lead to higher yields and in
many occasions, they have in fact produced lower yields.
- Dr. Charles Benbrook presented evidence that farmers who
use Monsanto's RoundUp Ready soybeans are getting lower yields
than farmers using conventional soybeans. (See: Campaign on Food
Safety News #20, 14 Jul 1999)
- Some researchers have shown that none of the GE seeds
significantly increase the yield of crops. Indeed, in more than
8,200 field trials, the Roundup Ready seeds produced fewer
bushels of soybeans than similar natural varieties, according to
a study by Dr. Charles Benbrook, the former director of the Board
on Agriculture at the National Academy of Sciences. (Peter
Rosset, "World Hunger: Twelve Myths")
- Recent experimental trials have shown that GE seeds do
not increase the yield of crops. A recent study by the USDA
Economic Research Service shows that in 1998 yields were not
significantly different in GE versus non-GE crops in 12 of 18
crop/region combinations. In the six crop/region combinations
were Bt crops or HRCs fared better, they exhibited increased
yields between 5-30%. Glyphosphate tolerant cotton showed no
significant yield increase in either region where it was
surveyed. This was confirmed in another study examining more than
8,000 field trials, where it was found that Roundup Ready soybean
seeds produced fewer bushels of soybeans than similar
conventionally bred varieties (United States Department of
Agriculture (1999) Genetically Engineered Crops for Pest
Management. USDA Economic Research Service, Washington, DC. As
cited in: "Ten reasons why biotechnology will not ensure food
security, protect the environment and reduce poverty in the
developing world"; Miguel A. Altieri, UC Berkeley and Peter
Rosset, Institute for Food and Development Policy, Oakland, CA)
- Dr Will McCarty, University of Mississippi Extension
Service Cotton specialist: "Before you plant transgenic
varieties, be sure you need the value-added trait. Also evaluate
the yields of varieties with the transgenic trait you desire, and
study the risk and benefit ratio, if any. In other words, if you
feel you need to plant Bt and the variety does not or has not
yielded well for you or in your area, consider the risk of not
using it and the potential cost of additional insect control
versus potential yield loss to planting it. The same can be said
for a transgenic variety for herbicide tolerance. Before you pay
extra for the convenience of using a particular herbicide
over-the-top, be sure the variety fits your farm and will yield
well. .... Also, transgenic varieties may not perform as well as
did their parents. Just because you have had good experience with
a particular variety does not mean you will have the same results
with a transgenic version." (Agronomy Notes, 5 Oct 1999)
- Dr Alan Blaine, soya bean specialist, University of
Mississippi extension service: "The vast majority of the problems
soybean growers have encountered over the last couple of years
have been on relatively new varieties. Instead of taking 6 to 8
generations for a variety to reach the market, we are seeing
varieties blown up and put on the market in probably 3 to 4
generations. It is this trend that has caused many of you to
experience poor performance from many new varieties. Steer away
from planting a variety just because someone tells you how good
it is. Prove it to yourself and this should be done with no less
than 2 years of yield test data. Variations in growing conditions
cause varietal differences to be expressed, and 1999 really
exposed some potential weakness in several varieties." (Agronomy
Notes, 5 Nov 1999)
-- Studies at the Department of Entomology, Ohio State
University by Hal Wilson indicate no yield difference between Bt
and non-Bt lines. At their Northwestern Station, 3 non-Bt maize
hybrids averaged corn borer injury of 1.08 cavities per plant
compared to 0.55 the previous week at the Western Station. In
1997 trials at the Northwestern Station, injury in non-Bt maize
averaged 1.66 cavities per plant, with no significant difference
in yields between the Bt and the equivalent non-Bt maize. This is
their third year of comparison trials. Over this 3-year period,
corn borer injury per non-Bt plant has averaged 0.54 cavities at
the Western Station and 0.74 at the Northwestern Station. The
results accumulated to date raise questions about the economic
benefits of Bt-maize hybrids if such technology must be purchased
at premium prices. (AgBiotecNet Oct 99)
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