Abstract: Long-term field trials on eight simulated models representing the fundamental types of fertilization system in China have been carried out from north to south at three field stations in the eastern humid region of China.The results indicate that the contribution of fertilization to crop yield was significantly influenced by the fertilization system adopted and the thermal condition of local climate.In the case of optimum fertilization system, the largest contribution rate was 30%(average of ten years) at Hailun station (temperate zone), 38%(six years) at Shenyang station (warmer temperate zone) and 44% (seven years) at Taoyuan station (subtropical zone), impling the existence of geographic differentiation controlled by the thermal factor of climate.Therefore, the largest contribution rate of fertilization in the forming of crop yield can be generally estimated from 30% to 45%, depending on the climate condition and with no change of other techniques adopted in farming.

Key words: Crop yield, Contribution of fertilization, Geographic differentiation