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Transgenic plants and their affect on soil health.

June 8, 2012

The growing use of transgenic plants within modern agriculture has sparked major debates as to the possible negative affects they could have on the environment. One of the major issues of debate is on what kind of affects these genetically modified plants may have on soil health. Some of the more popular transgenic plants being used today have been genetically modified to produce chemical compounds that have properties such as insect-resistance and herbicide-resistance. It has been found that these chemical compounds can be introduced into the soil either by the plant exuding them through their roots (Li et al, 2010), or by crop remains being plowed under after a harvest (Garcia and Altieri, 2005). One study found that an insecticide compound, produced by a transgenic cotton species, can remain in the soil for as long as 140 days after integration (Palm et al., 1996). The concern is that by accumulating within the soil, these compounds could have a major impact on the soil microbial community.

Most people don’t often consider the fact that soil in teeming with microorganisms, such as bacteria and fungi, which are responsible for maintaining soil health. It is said that within the soil 80-90% of all functions, such as decomposition and nutrient cycling, are carried out by microbes (Nannipieri and Badalucco, 2003). Knowing this, some people fear that an accumulation of these toxins produced by transgenic plants within the soil could kill off beneficial organisms which would be highly detrimental to soil functionality. Because of this concern there has been a recent boom in research studies to see if this is something we should be worried about.

Photo of a cotton plant in Texas taken by the USDA Natural Resources Conservation Service in 1996.

Most of the recent studies that I have found seem to indicate that there is no real discernable treat to soil microbial communities due to interactions with these compounds. In a recent 3 year study, Li et al. tested to see if an insect-resistant strain of cotton had any affect on the microbes living within the soil where it was grown. The results of their study indicated that there was no significant change in the diversity, or population sizes, of the studied microbial species living within the soil. As well they compared the data obtained from this soil to data obtained by studying the microbial composition of soil from a field growing a natural cotton species, which they used as a control. When comparing the results from the two, they found no difference between the two soil microbial compositions (Li et al., 2010).

Another recent study on this subject was performed by Chun et al. in which they tested to see if a transgenic species of rice, which had been modified to be herbicide-resistant, had any impact on the microbial organisms in the soil where it was grown. This study spanned over 2 years in which they grow both the transgenic rice as well as the original rice species from with the transgenic version was derived. Their results, and conclusions, were much the same as those Li et al. found in their study. Chun et al. found that there was no discernable difference in soil microbial composition or diversity between the two soils growing the target species, nor was there a change over time. (Chun et al., 2011).

Photo of a rice field in Burma by Ericwinny in 2009.

The finding of these two studies seem to be similar to those of other studies addresses this same issue, and they indicate that currently used transgenic plants are most likely having little to no affect on the soil microbial communities in which the are being grown. More research is still needed in this area, but for now it seems that there is one less thing to worry over when it comes to the integration of genetically modified plants into the environment.

 

References:

Chun, Young Jin, Hyo-Jeong Kim, Kee Woong Park, Soon-Chun Jeong, Bumkyu Lee,             Kyoungwhan Back, Hwan Mook Kim, and Chang-GI Kim. “Two-year Field Study Shows Little Evidence That PPO-transgenic Rice Affects the Structure of Soil Microbial Communities.” Biology and Fertility of Soils (2012): n. pag. Print.

Garcia, M. A., and Miguel A. Altieri. “Transgenic Crops: Implications for Biodiversity and Sustainable Agriculture.” Bulletin of Science, Technology & Society 25.4 (2005): 335-53. Print.

Li, Xiaogang, Biao Liu, Jinjie Cui, Doudou Liu, Shuai Ding, Ben Gilna, Junyu Luo, Zhixiang Fang, Wei Cao, and Zhengmin Han. “No Evidence of Persistent Effects of Continuously Planted Transgenic Insect-resistant Cotton on Soil Microorganisms.” Plant&Soil 338.1/2 (2011): 247-57. Print.

Nannipieri, P., and L. Badalucco. “Biological Processes.” Handbook of Processes and Modeling in the Soil-plant System. By Dinesh K. Benbi and Rolf Nieder. Binghamton: Haworth, 2003. Chp 3, 209. Print.

Palm, C.J., R.J. Seidler, D.L. Schaller, and K.K. Donegan. “Persistence in Soil of Transgenic Plant Produced Bacillus Thuringlensis Var. kurstaki δ-endotoxin.” Canadian Journal of Microbiology 42.12 (1996): 1258-262. Print.

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