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  • From: "TradingPostPaul" <tradingpost@riseup.net>
  • To: livingontheland@lists.ibiblio.org
  • Subject: [Livingontheland] Scientists Estimate That Pesticides are Reducing Crop Yields by ONE-THIRD
  • Date: Fri, 13 Jul 2007 07:40:11 -0600


http://www.organicconsumers.org/articles/article_5995.cfm
Scientists Estimate That Pesticides are Reducing Crop Yields by ONE-THIRD
The Organic Center, 7/10/2007
Straight to the Source

Over the last forty years nitrogen fertilizer use has increased seven-
fold and nearly every acre of intensively farmed, conventional
cropland is treated with pesticides. A team of scientists explored
the impact of pesticides and other environmental toxicants on
symbiotic nitrogen fixation (SNF) brought about by Rhizobium bacteria
(Fox et al., 2007). Their findings were published June 12, 2007 in
the prestigious Proceedings of the National Academy of Sciences (read
full study here).

The team describes the critical role played by SNF in supporting crop
yields and environmental quality. SNF has great potential to reduce
farm production costs – a factor of growing importance as rising
natural gas prices push upward the cost of nitrogen fertilizers. In
Brazil, SNF from soybeans reduces production costs an estimated $1.3
billion per year. The research by Fox et al. (2007) explored in depth
the signaling processes between plants and bacteria colonizing plant
roots – processes that govern the degree of SNF and the production of
certain phytochemicals. They focused on the ways that pesticides can
disrupt signaling and impair the efficiency of SNF. Some 30
pesticides are known to disrupt SNF; the most widely used pesticide
in the United States, glyphosate (Roundup) is known to be toxic to
nitrogen fixing bacteria.

The “Conclusions? section of the paper begins by stating:

“The results of this study demonstrate that one of the environmental
impacts of pesticides and contaminants in the soil environment is
disruption of chemical signaling between the host plants and N-fixing
Rhiz(obia) necessary for efficient SNF and optimal plant yield.?

Drawing on their recent work and other published studies, the team
projected that pesticides and other contaminants are reducing plant
yield by one-third as a result of impaired SNF. This remarkable
conclusion suggests one mechanism, or explanation of the yield-
enhancing benefits of well-managed, long-term organic farming systems.

Source: “Pesticides reduce symbiotic efficiency of nitrogen-fixing
rhizobia and host plants?

Authors: Jennifer E. Fox, Jay Gulledge, Erika Engelhaupt, Matthew E.
Burrow, and John A. McLachlan.

Proceedings of the National Academy of Sciences, Vol. 104, No. 24,
June 12, 2007.






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