Scientists Estimate That Pesticides are Reducing Crop Yields by ONE-THIRD

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Scientists Estimate That Pesticides are Reducing Crop Yields by ONE-THIRD

Through Impaired Nitrogen Fixation

July 2007

http://www.organic-center.org/science.hot.php?action=view & report_id=99

 

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.

http://www.pnas.org/cgi/content/abstract/104/24/10282

 

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.â€

 

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 plantsâ€

 

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.