Abstract: 【Objective】Changes in soil nutrients and process of soil carbon accumulation following the conversion of desert sandy land to irrigation cropland in arid region in northwest China is an important indicator for evaluating oasis ecosystem structure, function and productivity evolution. It is also one of the aspects for understanding soil development process and its evolution patterns on the newly cultivated farmlands in arid region.【Method】In this study, the temporal changes in soil physical and chemical properties in the 0-60 cm soil layers were determined in a 0-46 year cultivation sequence in the Linze marginal oasis. Soil properties in the plough layer (0-20cm) between 2008 and 2014 were compared to determine the changes of soil properties within the recent 6 years.【Result】The results indicated that sand content in the 0-20cm surface layer showed a consistent decreasing pattern with increasing duration of cultivation, but significant changes in particle size distribution only occurred in soils cultivated for more than 16 years. Within the recent 10 years, no significant changes in soil particle size distribution were detected. As cultivation time increased, soil organic carbon (SOC), total N and available N and P concentrations all increased. SOC and total N showed a rapid and linear increase in the initial 20 years after cultivation, and thereafter, had a slow increase. SOC, total N, and available N and P concentrations increased by 9.0 times, 6.3 times, 6.3 times and 13.5 times, respectively, after 46 years of continuous cropping. Soil inorganic carbon (SIC) increased by 77.1% after cultivation of 46 years. Available K concentration showed a decrease in the initial 20 years of cultivation, and subsequently, had a rapid increase. Also, SOC, N, P and K concentrations in the 20-40 cm and 40-60 cm soil layers gradually increased with increasing cultivation time, but the increase extent was far less than that of surface soil. During the 6 years period from 2008 to 2014, no significant changes in soil particle size distribution in the plough layer were found, however, SOC, N, P and K nutrients showed a distinct accumulation. After 46 years of continuous cropping, SOC, SIC and total C sequestration rate was 0.75, 0.79 and 1.47 kg·hm^-2·a^-1, respectively. SOC accumulation occurred mainly in the surface soil, SIC accumulation was found in the 40-60 cm soil layer. Conversion of sandy desert soils to irrigation croplands had a tremendous soil carbon sequestration potential. The increased silt and clay content play an important role in SOC and nutrients accumulation and retention.【Conclusion】After cultivation of native sandy lands and subsequently, continuous cropping improved significantly soil fertility. However, soil fertility was still in a low status after 46 years of cropping. Therefore, improved agricultural management is imperative to accelerate soil fertility improvement and maintain long-term productivity of the newly reclaimed sandy farmlands.

Key words: changes in soil properties, soil carbon accumulation, cultivation sequence, desert sandy land, oasis in Hexi Corridor Region