Study Says Pesticides Block Crops' Natural Nitrogen Production

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Study Says Pesticides Block Crops' Natural Nitrogen Production

http://www.organicconsumers.org/articles/article_5513.cfm

* ENS - Environment News Service, June 6, 2007

Straight to the Source

 

EUGENE, Oregon, June 6, 2007 (ENS) - Farmers applying pesticides

intended

to boost crop yields may instead be contributing to plant growth

problems,

University of Oregon scientists report in a new study.

 

The research revealed that artificial chemicals in pesticides disrupt

natural nitrogen-fixing communications between crops and soil

bacteria.

 

The disruption results in lower yields or in delayed growth whether

the

pesticides are applied deliberately or reach the crops through runoff.

 

In a paper appearing online this week ahead of the regular publication

by

the Proceedings of the National Academy of Sciences, the five-member

team

reports that pesticides bind to and block connections to specific

receptors

inside rhizobia bacteria living in root nodules in the soil.

 

Rotation legume crops such as alfalfa and soybeans require such

interaction

to naturally replace nitrogen levels that, in turn, benefit primary

market

crops like corn grown after legume rotations.

 

Alfalfa roots secrete chemical signals into soil to attract and

recruit

bacteria. These bacteria live in a plant's roots and provide a natural

fertilizer source.

 

Legume plants secrete chemical signals that recruit the friendly

bacteria,

which work with the plants to convert atmospheric nitrogen into

ammonia

that, then, is used as fertilizer by the plants.

 

" Agrichemicals are blocking the host plant's phytochemical recruitment

signal, " said the study's lead author, Jennifer Fox, a postdoctoral

researcher in the Center for Ecology and Evolutionary Biology at the

University of Oregon.

 

" In essence, the agrichemicals are cutting the lines of communication

between the host plant and symbiotic bacteria, " she said.

 

" Our research provides another explanation for declining crop yields, "

Fox

said. " We showed that by applying pesticides that interfere with

symbiotic

signaling, the overall amount of symbiotic nitrogen fixation is

reduced. "

 

" We feel that this is a previously unforeseen factor contributing to

declining crop yields, " she said. The researchers say that field-wide

experiments now are needed, in addition to tests to determine the

exact

elements of pesticides that inhibit natural plant-bacteria interaction.