Abstract: The constant equal relation R=2-2/100 and R=200.5- were discovered in the commonly used duality function of the fertilizer effect. In above mentioned constant equal formula R is production incresing rate which represents the percentage of increased production and maximum increased production, is the proper fertlizer ratio which represents the percentage of fertilizer application amount for maximum increased production. According 1o above mentioned constant equal relation, the introduced fertilizer application amount could be reduced 20% compared with the introduced fertilizer application amount calculated directly with the duality (unction on the fertilizer effect. The application of this new concept is vrey important for increasing the fertlizer application effect and reducing the pollution caused by fertilizer to the environment.