The global population is expected to increase by two to three billion people by 2050, a projection raising serious concerns about sustainable development, biodiversity and food security, but new research led by Princeton University shows that more efficient use of nitrogen fertilizers may address both environmental issues and crop production.Today, more than half of the world's population is nourished by food grown with fertilizers containing synthetic nitrogen, which is needed to produce high crop yields. Plants take the nitrogen they need to grow, and the excess is left in the ground, water and air. This results in significant emissions of nitrous oxide, a potent greenhouse and ozone-depleting gas, and other forms of nitrogen pollution, including chemical over-enrichment of lakes and rivers and contamination of drinking water.