Abstract: The use of great quantities of fertilizer in agricultural production is one of the causes of generation of non-point source pollution(NPS) in the Yangtze River delta economic zone.Based on the statistics of farming production and agricultural produce market during 1980-2005,economic incentives of the fast growth rate were explored from the angle of changing opportunity cost of input factors,and changing prices of agricultural produce.Results show that land opportunity cost grew much faster than the prices of fertilizers,thus leading to substitution of land with fertilizer;that rapid growth of labor opportunity cost led to substitution of labor with fertilizer;and that prices of the labor intensive agricultural produce fluctuated sharply,which are assumed to be the major contributors to the rapid growth of fertilizer input.