The yield of any crop is dependent upon the environment in which we expect it to grow and the management practices we impose on the cropping system. Current estimates are that about 70% of the variation in yield from year to year is dependent upon the environment and only 30% of the variation is subject to management. The major environmental constraints include the weather, the soil system, and pests. Management practices must be designed and implemented to minimize the risk of adverse environmental conditions drastically reducing yields, and maximize the opportunity to take advantage of above average environmental conditions during the growing season. Physiology is a study of developmental and metabolic systems that are responsible for growth and development of any organism. Current physiological research which is designed to develop a comprehensive understanding of those developmental and physiological processes most responsible for crop growth and productivity should produce a better production system.