Effect of soil fertility and long-term fertilizer application on the yields of wheat and maize in Fluvo-aquic soil

Long-term trends of crop yields and soil fertility have been used as a means to evaluate the sustainability of intensive agriculture, soil management and fertilizer application. Effect of soil fertility and long-term fertilizer application on the tendency of wheat and maize yield was analyzed based on 24-year data (1987-2010) collected from 32 sites, two treatments (no-fertilizer and normal fertilizer, which means NPK with straw) of long-term experiment of Drab Fluvo-aquic soil. The results showed that the average contribution rate of soil fertility to wheat and maize yield was 51.4% and 54.0%, separately. And the coefficient of variation (CV) of the contribution rate was 39.0% in wheat season, and 41.2% in maize season. The yields of wheat and maize in no-fertilizer field decreased slowly at a rate of 4.1kg/hm2 and 96.6 kg/hm2 per year, separately. In normal fertilizer application field, the yields of wheat and maize increased at a rate of 61.5 kg/hm2 and 26.8 kg/hm2 per year, separately. There was significant positive relationships between the amount of fertilizer and yield increase (yield in fertilized treatment yield in unfertilized treatment). Path analysis of the relationship between fertilizer, soil fertility and crop yield confirmed that N fertilizer amount had significant direct effect on wheat yield. Phosphate fertilizer also had an important effect on the wheat and maize yield. In conclusion, crop yield in Drab Fluvo-aquic soil decreased slowly under no fertilizer condition, increased slowly under fertilizer treatment.