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[SANET-MG] nitrogen composition of organic and conventional crops
J. Agric. Food Chem., 55 (7), 2664 -2670, 2007. 10.1021/jf0627726
S0021-8561(06)02772-5
Web Release Date: March 7, 2007
Nitrogen Isotope Composition of Organically and Conventionally Grown Crops
Alison S. Bateman, Simon D. Kelly,* and Mark Woolfe#
School of Environmental Sciences, University of East Anglia, Norwich NR4
7TJ, United Kingdom; Institute of Food Research, Norwich Research Park,
Colney, Norwich NR4 7UA, United Kingdom; and Food Standards Agency,
Aviation House, 125 Kingsway, London WC2B 6NH, United Kingdom
Received for review September 27, 2006. Revised manuscript received
January 8, 2007. Accepted January 25, 2007. This work was financed by
the U.K. Food Standards Agency as part of its Food Authenticity and
Labelling Programme, Project Q01076. The views expressed in this paper
are those of the authors and do not necessarily reflect the views of the
U.K. Food Standards Agency.
Abstract:
Authentic samples of commercially produced organic and conventionally
grown tomatoes, lettuces, and carrots were collected and analyzed for
their 15N composition in order to assemble datasets to establish if
there are any systematic differences in nitrogen isotope composition due
to the method of production. The tomato and lettuce datasets suggest
that the different types of fertilizer commonly used in organic and
conventional systems result in differences in the nitrogen isotope
composition of these crops. A mean 15N value of 8.1” was found for the
organically grown tomatoes compared with a mean value of -0.1” for those
grown conventionally. The organically grown lettuces had a mean value of
7.6” compared with a mean value of 2.9” for the conventionally grown
lettuces. The mean value for organic carrots was not significantly
different from the mean value for those grown conventionally. Overlap
between the 15N values of the organic and conventional datasets (for
both tomatoes and lettuces) means that it is necessary to employ a
statistical methodology to try and classify a randomly analyzed "off the
shelf" sample as organic/conventional, and such an approach is
demonstrated. Overall, the study suggests that nitrogen isotope analysis
could be used to provide useful "intelligence" to help detect the
substitution of certain organic crop types with their conventional
counterparts. However, 15N analysis of a "test sample" will not provide
unequivocal evidence as to whether synthetic fertilizers have been used
on the crop but could, for example, in a situation when there is
suspicion that mislabeling of conventionally grown crops as "organic" is
occurring, be used to provide supporting evidence.
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