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%,respectively.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 4.1 kg/ha and 96.6 kg/ha per year,respectively.In normal fertilizer application field,the yields of wheat and maize increased at a rate of 61.5 kg/ha and 26.8 kg/ha per year,respectivelyy.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.