Abstract: High speed development of agriculture needs the input of chemical fertilizer. However, over use of fertilizer will induce man-made pollution, harm directly human’s health and threaten human’s living environment. It is found that maximum suggested fertilzer application rate is not the best method to be adopted. The results of experiments and theoiy inference indicate that even the suggested fertilizer application rate reduce by 20%, the crop yield will not decrease by more than 2%. This result is benefit in increasing fertilizer availability and reducing chemical fertilizer pollution.