Plant Nutrition--Roots of Life for Fundamental Biology and Better Crop Production

The world's population reached 6.7 billion in 2008 and continues to grow. 2008 was also a year marked by high food prices, and indeed food crises have arisen in developing countries. Given the increase in population and decrease in available arable land, the public expects us, the plant science community, to provide technologies that maintain and increase food production. Plants grow in the soil, take up mineral nutrients and generate food for us. Therefore, the uptake of mineral nutrients by plants from the soil is a critical step, in terms of both food production and global element cycling. The human body contains about 1.5 kg of nitrogen atoms. Every human eats nearly three times this quantity of nitrogen every year in the form of protein, equivalent to 73 g of protein a day. The current world population consumes some 28 million tonnes of protein-nitrogen every year. Eighty-five percent of the nitrogen in food proteins comes from agriculture, either directly in plant-derived foods or indirectly via animals fed with plant material. Synthetic fertilizers derived from the Haber–Bosch synthesis of ammonia provide 44–51% of all the nitrogen absorbed by crops. Therefore, roughly 40% of nitrogen in foods derives from synthetic ammonia (Smil 2002). Nitrogen fertilizers were first introduced using the few natural deposits of nitrate salts such as Chilean nitrate, and as ammonium sulfate produced as a by-product from gasworks, but the Haber process was established on an industrial scale in 1913 and has since ensured unlimited supplies from atmospheric nitrogen (Jenkinson 2001).