Maize is widely cultivated throughout the world, and a greater weight of maize is produced each year than any other grain.The United States produces 40% of the world’s harvest; other top producing countries include China, Brazil, Mexico, Indonesia, India, France and Argentina. Worldwide production was 817 million tonnes in 2009\u2014more than rice (678 million tonnes) or wheat (682 million tonnes). In 2009, over 159 million hectares (390 million acres) of maize were planted worldwide, with a yield of over 5 tonnes per hectare (80 bu\/acre). Production can be significantly higher in certain regions of the world; 2009 forecasts for production in Iowa were 11614 kg\/ha (185 bu\/acre). There is conflicting evidence to support the hypothesis that maize yield potential has increased over the past few decades. This suggests that changes in yield potential are associated with leaf angle, lodging resistance, tolerance of high plant density, disease\/pest tolerance, and other agronomic traits rather than increase of yield potential per individual plant.<\/p>\n