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Re: [SANET-MG] nitrogen composition of organic and conventional crops



Hello Joe Nessim,
The article states :"Synthetic nitrogen fertilizers tend to have stable nitrogen isotope values close to zero, usually between -2 and 2 . The nitrogen in these fertilizers is derived from atmospheric nitrogen (15Natm = 0 ), and there is little fractionation during their manufacture. Fertilizers that may be permitted in organic farming include animal manures, composts, bloodmeal, fishmeal, hoof and horn, rapemeal, and seaweed-derived products. Manure is probably the most commonly applied source of nutrients in organic systems, and nitrogen isotope values between 10 and 20 are typically reported for manure-based fertilizers " I think that they mean compost rather than manure in organic certification but compost should have the the manure type on nitrogen isotopes. Biological nitrogen content differs from synthetic nitrogen fertilizers because enzymes in cells can discriminate between the mass isotopes and to concentrate the mass isotope N fifteen. The paper provides a way that imports of organic crops can be double checked to insure that they have not been grown with synthetic fertilizers.I should remind everyone that mass isotopes are not radioactive! Furthermore, it may be possible to correlate nitrogen isotope content of foods with health benefits, not that nitrogen isotopes themselves improve health but their presence may signal the presence of the compounds that make food healthy and to taste better. Hope this helps without being confusing. sincerely, joe cummins
Joe Nessim wrote:
From: jcummins <jcummins@UWO.CA>


Nitrogen Isotope Composition of Organically and Conventionally Grown Crops

Alison S. Bateman, Simon D. Kelly,* and Mark Woolfe#
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.

Do these differences have any biological significance? How exactly are they explained? Joe N.

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