Nitrogen is the main nutrient that limits crop yield. Biologically reactive nitrogen is therefore routinely supplied to crops as synthetic nitrogen fertilizer. In the developed world, the extensive use of synthetic fertilizer in agriculture has substantial financial and environmental costs. By contrast, in the developing world, the lack of fertilizer causes low crop yields, resulting in hunger and malnutrition. Many of these problems could be avoided if plants could be engineered to fix nitrogen directly from air.
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The economic benefits of biological nitrogen fixation by plants could be substantial. Globally, over $100 billion per year is spent on fertilizers, and the environmental costs are even greater.
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With adequate funding, it should be possible within the next decade or so to create a transgenic plant that can fix nitrogen at biologically significant rates. However, the real challenge will be to demonstrate that a plant can fix significant amounts of nitrogen, consistently, in the field. Given the present understanding of the biochemical basis of nitrogen fixation and its genetic determinants, as well as technical advances in plant transformation and organellar targeting, and a concerted research effort, the dream of a nitrogen-fixing crop plant in the field could be achieved within the next several decades.
