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nafex - Re: [NAFEX] nafex Digest, Pesticides Disrupt Nitrogen Fixation

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  • From: "Mark & Helen Angermayer" <hangermayer@isp.com>
  • To: "North American Fruit Explorers" <nafex@lists.ibiblio.org>
  • Subject: Re: [NAFEX] nafex Digest, Pesticides Disrupt Nitrogen Fixation
  • Date: Thu, 3 Jan 2008 21:34:01 -0600

Interesting article. However, I'm not sure what they mean when they say,
"The observations also may explain a trend in the past 40 years toward
stagnant crop yields despite record high use of pesticides and synthetic
fertilizers worldwide."

In the U.S, yields for row crops for the last 30 years (could not find data
for 40 years) show a soybean yield of just over 30 bu/ac in 1977 to over 41
bu/ac in 2007. Similarly, national average corn yield was 90 bu/ac in 1977
and increased to 153 bu/ac for 2007. Who knows what will happen in the
future, but as of yet, the trend doesn't appear to be leveling off.

http://www.nass.usda.gov/Charts_and_Maps/Field_Crops/cornyld.asp

Mark
KS


----- Original Message -----
From: <oowonbs@netscape.net>
To: <nafex@lists.ibiblio.org>
Sent: Thursday, January 03, 2008 4:56 PM
Subject: Re: [NAFEX] nafex Digest, Pesticides Disrupt Nitrogen Fixation


> This was worth it...
> Cariage returns added, deleted.
> Poor, but readable.
> BillSF9c
>
> From: Hilborn.E@epamail.epa.gov
> Subject: [NAFEX] Pesticides Disrupt Nitrogen Fixation
>
> Interesting news from the journal Environmental Health Perspectives
>
> http://www.ehponline.org/docs/2007/115-12/forum.html#pest
>
>
>
>
> PesticidesDisruptNitrogenFixation Talkaboutaviciouscycle. Some
> organochlorine pesticides
> suppressnitrogen-fixingbacteria fromreplenish ingnatural
> nitrogenfertilize rinsoil, resultinginlower cropyields,
> stuntedgrowth, andanever-grea terneedfor additivestoboost
> production.This previously unrecognized effectstems
> frompesticides interferingwith flavonoid signaling from leguminous
> plants suchas
> alfalfa, peas,and soybeans tosoil bacteria thatfix nitrogen.
> "People assume that endocrine disruptionby pesticides occurs only in
> humans and animals with estrogen receptors
> ,but we find thereare nontradit ional targets affected by pesticide
> s,"says Jennifer
> Fox,a postdoctoral researcher at the Center for
> Ecology and Evolutionary Biology at the
> University of Oregon.
>
> (Embeddedimagemovedtofile:pic10069.jpg)Rhizobiuminfects
> alfalfaroots
>
> image:DanGage/courtesyofJournalofBacteriology
>
> Plants produce chemicals ,many that are structura lly similar to
> phytoestrogens, that attract
> Rhizobium soil bacteria to their root systems toform nodules for
> nitrogen fixation. Inside the
> nodules, the bacteria convert atmospheric nitrogen into the natural
> fertilizer ammonia. These
> symbiotic soil bacteria respond to plant-produced flavonoid molecules
> through nodulationD (NodD) receptors ,which
> act similarly to estrogen receptors in vertebrat es. In theMay 2004
> issue of EHP,Fox and colleagues reported astudy using Sinorhizo bium
> meliloti,
> a soil bacterium that fixes nitrogen in symbiosis with alfalfa.
>
> The researchers found that the organochl orine pesticides
> pentachlo rophenol (PCP)and methyl parathion atlevels foundin farm
> soils inhibited
> NodD signaling by90% and that DDTcut signaling by45%.
> In recent greenhouse experiments, Fox and colleague sat Tulane
> University treated alfalfa seeds inoculate dwithS. meliloti withPCP,
> methyl parathion ,and DDT,
> which are found in soil after farmers spray crops, especially in
> countries where these pesticides have not been banned.
>
> Sixweeks after treatment,
> PCP-treated alfalfa plants produced no nodules, and plant yields fell
> to 17% compared with control
> plants not treated with pesticides. Methyl parathion and DDT reduced
> nodule numbers and plant yields by about half.The
> researchers estimate that the amount of inhibition measured in this
> experiment could translate in real-world
> conditions to a one-third loss of plant yield each growing season. The
> results, published 12June 2007in
> the Proceedings of the National Academy of Sciences, indicate
> that pesticide residues in soil could not only reduce harvest yields,
> but also increase the need for
> synthetic fertilizers, thereby raising costs for farmers and
> contributing to environmental
> pollution. The observations also may explaina trendin the past
> 40 years toward stagnant crop yields despite record highuse of
> pesticides and synthetic fertilizers worldwide.
> In unpublished experiments, co-author John McLachlan, director of the
> Tulane Center for
> Bioenvironmental Research showed that the same three pesticide sdisrupt
> NodD signaling in
> Rhizobium sp. strain NGR234,a bacterium that fixes nitrogen in
> symbiosis with more
> than 100 leguminous plants growing in tropical and subtropic alsoils.
>
> "Many of the species that NGR234 nodulatesare trees
> and bushes, such as teakand rosewood, that promote vital soil
> improvement within nutrient-poor tropical
> soils," he says. McLachlan says farmers in poorer countries especially
> cannot afford
> to lose natural fertilizer because synthethic fertilizers cost so much.
>
> The connection between pesticides and nitrogen fixation
> shows that "pristine and natural interactions between bacteria and
> plants are being
> jeopardized by what we put into the soil," says Ann Hirsch,
> a plant
> molecular biologist at the University of California, Los Angeles.
>
> Similarly, the effects of pesticide son human disease continue to be
> documented, with a
> report in the October 2007 issue of EHP
> linking childhood exposure to DDT with a fivefold higher risk of breast
> cancer in women.
> "Now we are affecting our agricultural assets,
>
> "Hirsch says, "something people take for granted." Fox plans to test
> the effects of pesticide son alfalfa and soybeans
> under real-life field
> conditions."Wewanttoscreenpesticidestoseewhichonescauseminimaldamagetocer
> taintypesofcropsand
> maximizetheamountofnaturalfertilizermade,"shesays.
>
> Carol Potera
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