Soybean requires at least 2400 Corn Heat Units in one growing season. Cultivated soybean is adapted to a wide range of latitudes, from 52N˚ to 50˚s, and to a range of seasonal durations (90 to 180 days). The four major producers, USA, Brazil, China, and Argentina, together account for 90 to 95% of the world’s production. Canada is at northern limit of the North American soybean growth range, but soybean production there has risen sharply in recent times. Temperature is usually the limiting climatic factor in short growing season areas, such as Canada