ABSTRACT
During the past 30 years, both the size of the world population and the production of crops to feed these people have increased considerably. Based on data of the Food and Agriculture Organization (FAO) of the United Nations, production of the common crop groups increased by 47% between 1985 and 2005, although if all of the 174 crops covered in the FAO reports are considered this increase is approximately 28% (Foley et al., 2011). In this time period, the area of cropland only increased by 2.4% (although taking into account multiple cropping, the decreasing proportion of land left fallow, and decreasing incidence of crop failures, the area of cropland that was harvested increased by 7%). This means that average crop yields per unit land area increased by 20% between 1985 and 2005 (Foley et al., 2011). These yield increases were brought about by advances in crop production techniques, including in the use and application of fertilizers.
