Abstract: 【Objective】 Based on field experiments established on newly cultivated sandy farmlands in marginal oasis in the middle reaches of Heihe River Basin, the short-term effects of different fertilizations, mulching and tillage, cultivation pattern on soil organic carbon (SOC), total nitrogen (TN) and carbon fractions were determined. The aim is to provide information for rapid enhancement of soil organic matter and soil fertility under soil management measurements. 【Method】 The concentrations of SOC, TN, and carbon fractions including particulate organic carbon (POC), hot-water extractable organic carbon (HWC), easily oxidation organic carbon (EOC) and microbial biomass carbon (MBC) were analyzed under different treatments of different agricultural managements. 【Result】The results showed that SOC and TN concentrations at the tillage layer (0-20 cm) under the treatments of farmyard manure application alone and combined manure with chemical fertilizers increased by 32.1%-98.7% and 1.5%-40.9% in comparison with the initial values 6 years ago at the beginning of experiment, with the highest increase in the treatment of maximum manure application alone. However, SOC and TN were still at very low levels, similar to the levels at the beginning of experiment under application of maximum N, P, and K chemical fertilizers alone. Following four years of different mulching and tillage managements, SOC and TN concentrations increased by 5.4%-34.0% and 9.3%-34.9%，with the highest increase in the straw mulching combined with reduced tillage treatment (RSM). RSM treatment increased SOC concentration by 27.2% compared with the plastic film mulching combined with conventional tillage (CK), while the short-term effect of reduced tillage on SOC was not significant under straw and plastic film mulching. SOC concentration increased by 72.7% and 27.7% under alfalfa field for 10 years and field for 5 years alfalfa following 5 years maize, respectively, compared to continuous 10 years maize treatment. Correspondingly, total N increased by 54.3% and 17.1%. The variation tread in POC, EOC, HWC and MBC among different treatments of different management practices was in accord with that of SOC, but the differences among treatments were more significant than that of SOC. The percentage of POC to SOC was greatly significant in the maximum manure application alone, straw mulching with reduced tillage and alfalfa for 10 years than that in the corresponding other treatments. 【Conclusion】Increasing manure application, returning crop residues to soil, and planting perennial alfalfa or placing alfalfa in crop rotation regime are effective measures for rapid increase of SOC and enhancement of soil quality following the conversion of sandy desert to irrigation farmland in arid region. POC is suggested as a sensitive indicator for reflecting the shot-term effect of agricultural management practices on SOC dynamics.

Key words: fertilization, mulching and tillage, cultivation pattern, soil organic carbon, carbon fractions, sandy desert soil