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ARS Home » Midwest Area » Columbia, Missouri » Cropping Systems and Water Quality Research » Research » Publications at this Location » Publication #158141
Title: IMPACT OF GENETICALLY-MODIFIED CROPS AND THEIR MANAGEMENT ON SOIL MICROBIALLY-MEDIATED PLANT NUTRIENT TRANSFORMATIONS

Author
item MOTAVALLI, PETER - UNIV OF MO
item Kremer, Robert
item FANG, MIN - UNIV OF MO
item MEANS, NATHAN - UNIV OF MO

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2004
Publication Date: 5/1/2004
Citation: Motavalli, P.P., Kremer, R.J., Fang, M., Means, N.E. 2004. Impact of genetically modified crops and their management on soil microbially mediated plant nutrient transformations. Journal Environmental Quality. 33(3):816-824.

Interpretive Summary: The public is concerned about genetically modified (GM) crops growing on farms throughout the U.S. Although the majority of consumers believe that food from GM crops is generally healthy and nutritious, they are concerned about the possible effects these crops might have on environmental quality. GM crops undergo testing similar to standard pesticide evaluations. However, important biological functions in soils and around plant roots have been largely neglected in evaluation of GM crops. Some of the biological functions include decomposing dead plant material, causing important nutrients to be available to plants and making substances that give soils the structure to withstand erosion. Our objectives were to survey the available information related to the environmental effects of GM crops on soil biological functions. Certain GM plants may affect soil biological processes; however, we do not know whether these effects are from chemicals leaking from roots (exudates) or from some other process in the GM plant. A wide variety of GM crops will continue to be introduced on large areas of farmland in the future. We suggest that additional research is needed to improve our understanding of the make-up of GM plants and how this material affects biological functions in soils. Therefore, how GM plants affect the biology of soils needs to be considered in a thorough assessment of GM crops. This information has important implications for soil and crop scientists at all levels (government, University, and industry) because of the public demand for a more comprehensive environmental assessment of GM crops that are currently widely planted throughout the U.S.

Technical Abstract: Transgenic crops were cultivated on approximately 44 million hectares world-wide in 2000. Alteration in soil biological processes mediated by microorganisms may be a potential effect of widespread transgenic crop production. Soil microorganisms function in soil organic matter decomposition, nutrient mineralization and immobilization, oxidation/reduction reactions, biological N fixation, and mineral solubilization. The direct and indirect effects of transgenic crops on microbially-mediated nutrient transformations in soils have received little attention. The objectives of this paper are: to review the available literature related to the environmental effects of transgenic crops and their management on nutrient transformations mediated by soil microorganisms; and, to consider soil and climatic factors that may affect impacts of transgenic crops on soil biological processes. Genetic modification of crops has focused on improving plant nutrition. Improved plant nutrition traits include greater plant tolerance to low Fe availability in alkaline soils, enhanced acquisition of soil inorganic and organic P, and increased assimilation of soil N. Soil microbial activity may be changed by transgenic crops due to differences in quantity and content of root exudates, gene transfer from crop material to microorganisms, and management practices altered for transgenic crop production. Changes in management may include different ingredients, application rates and times of pesticides; altered tillage practices; and composition and application rates of inorganic and organic fertilizer sources. The composition of transgenic crops may affect residue decomposition and soil erosion. Transgenic crops, modified for herbicide or pest resistance, have not been conclusively shown to affect stimulation or suppression of soil nutrient transformation under field conditions. Assessment of transgenic crops should also include effects of a wide range of soil properties, including clay type and mineralogy, pH, soil structure, and soil organic matter; and variations in climatic conditions. Thorough environmental evaluations are needed to improve our understanding of the impacts of diverse transgenic crops on soil biological functions and processes including soil nutrient transformations.