Abstract: The objective of this study was to discuss the effects of long-term different fertilization treatments on soil fertility and soil organic carbon (SOC) accumulation in sandy soil of oasis farmland using a long-term field fertilization experiment started in 2005. The experiment treatments include 9 treatments with different amount of organic manure, chemical fertilizers, and combined application of different amount of organic and inorganic fertilizers. The characteristics in soil physical and chemical properties and dynamic changes in soil organic carbon (SOC) under different fertilization treatments were determined in tillage layer (0-20 cm). The results indicated that soil bulk density decreased 0.13 g·cm^-3 and field water capacity increased 6.7% in the treatments of manure application alone and combined application of different amount of organic and inorganic fertilizers compared with the treatments of chemical fertilizers application alone on average. SOC concentration in the treatments of manure application alone and combined application of organic and inorganic fertilizers increased by 64.8% and 36.3%, respectively, in comparison with the treatments of chemical fertilizers. Also, total nitrogen concentration increased by 64.9% and 49.5%, respectively. The treatments of high amount of NP fertilizers and NPK fertilizers showed a higher total phosphorus concentration than that of other treatments. Alkali-hydrolyzable N concentration was significantly higher in the treatments of manure application alone and combined application of organic and inorganic fertilizers than in the treatments of inorganic fertilizers. Available K concentration increased significantly under high amount of manure application. Under different fertilization treatments for ten consecutive years, SOC concentration increased by 1.68-2.84 times in comparison with the initial value. Total N, Total P, Alkali-hydrolyzable N and available P concentrations increased in different degrees. However, available K concentration declined under application of inorganic fertilizers alone and combined application of manure and NP fertilizers. On average, SOC accumulation rate was 0.27, 0.59 and 0.87 g·kg^-1·a^-1 under manure application alone, inorganic fertilizers application alone, and combined application of organic and inorganic fertilizers, respectively. Increasing organic fertilizer input, reducing moderately inorganic fertilizers input, and balanced application of manure and NPK chemical fertilizers were effective measures for improving soil fertility for oasis sandy farmland.

Key words: long-term fertilization experiment, change in soil fertility, soil organic carbon dynamics, oasis sandy farmland