viernes, marzo 12, 2010

Matt Ridley's nitrogen nonsense

E-mail NOTE: For Ridley's original Economist piece (The new NUE thing) and our previous comment on it see:
Ridley's nitrogen nonsense

GM Watch UK

Matt Ridley's Economist piece claims GM crops will solve the coming nitrogen crisis. Chemical agriculture relies on synthetic nitrogen fertilizer, which is made from fossil fuels and takes huge amounts of energy to make – so everyone knows synthetic nitrogen is on the way out. Ridley says specially designed GM crops are yielding more with less nitrogen fertilizer.

But according to a report by the Union of Concerned Scientists (No Sure Fix: Prospects for Reducing Nitrogen Fertilizer Pollution through Genetic Engineering), traditional breeding methods have already proven successful at developing crops that use nitrogen more efficiently.

The biotech industry has identified genes that have the potential to reduce nitrogen pollution and have tested them in laboratories and field trials, but none are commercially available. The UCS report evaluated the new genes and concluded that the prospects for their commercial use are uncertain due to the complexity of nitrogen metabolism and genetics in crops.

The only non-GM methods of adding nitrogen to soil that Ridley seems to know about are adding animal manure and growing legumes. Thus he concludes that organic farming can't produce enough nitrogen. But organic systems manage nitrogen in many interrelated ways, as studies confirm:

*Organic soils retain nitrogen better, meaning there's less of the nitrogen runoff that is one of chemical agriculture's worst pollution problems. (Pimentel, D. et al., Environmental, Energetic, and Economic Comparisons of Organic and Conventional Farming Systems, Bioscience, Vol. 55, No. 7, July 2005, pp. 573–582,

*Organic systems don't only focus on adding nitrogen to soil – but on decreasing nitrogen loss. An analysis of crop yield and nitrogen dynamics reported that the use of legume cover crops reduced nitrate leaching by 40% on average (Tonitto, C., David, M. B., & Drinkwater, L. E. (2006). Replacing bare fallows with cover crops in fertilizer intensive cropping systems: A meta-analysis of crop yield and N dynamics. Agriculture, Ecosystems and Environment, 112, 58–72)

*A 2007 University of Michigan study that compared organic yields to conventional concluded, "Data from temperate and tropical agroecosystems suggest that leguminous cover crops could fix enough nitrogen to replace the amount of synthetic fertilizer currently in use." (Badgley, C., et al., Organic agriculture and the global food supply, Renewable Agriculture and Food Systems , Vol. 22, No. 2, July 2007, pp. 86–108)

*One study calculated the potential nitrogen production by leguminous plants via intercropping and off-season cropping to be 154 million tonnes, a potential which far exceeds the nitrogen production from fossil fuel. (Organic farming and climate change, International Trade Centre UNCTAD/WTO. Doc. No. MDS-08-152.E. Geneva: ITC, 2007, pp. 9-10)

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