Effects of Long-term Located Chemical Fertilizer Application on Yield and Soil Fertility

The long- term located experiment for 21 years was carried out on an irrigated desert soil in Hexi corridor, Gansu province. The results showed that the yield- increase effect of chemical fertilizer was the most significant in all treatments. The effect of long- term balanced chemical fertilizer application on soil nutrients was different. The content of organic matter in soil declined by 24.9%- 27.4% but the content of soil total nitrogen was (TN) increased by 13.7% - 46.1% . The content of available N declined, but the content of soil total phosphate (TP) and available phosphate were increased by 4.4%- 5.1% and 6.3%- 19.1%, respectively. The K content in the soil was deficient, so the content of available K decreased gradually. The effect of indirect developing soil fertility of chemical fertilizer was very significant. The proportion of N, P and K in soil came from organic manure was 27.1%- 31.3%,23.8%- 27.0% and 33.2% of total inputs through biocycle.