[Contribution of fertilization development to yield production and its geographic differentiation]

The results of long-term field experiments at three stations in different areas of China indicated that the contribution of fertilization to crop yield was significantly affected by the thermal condition of climate and the fertilization system. In the case of optimum fertilization, the largest contribution rate was 0.31 (average of fourteen years) at Hailun Station (in temperate zone), 0.39 (average of twelve years) at Shenyang Station (in warmer-temperate zone), and 0.42 (average of eleven years) at Taoyuan Station (in subtropical zone), which showed that the existence of geographic differentiation was caused by the thermal condition of local climate. Therefore, keeping the optimum fertilization systems, the largest contribution rate to crop yield could be estimated from 30% to 50%, depending on the local climate condition. The interaction of fertilization and thermal factor between Shenyang and Taoyuan was much bigger than that between Shenyang and Hailun. The interaction between organic manure and thermal condition of local climate was bigger than that between chemical fertilizer and thermal condition of local climate.