Abstract: 【Objective】 To improve the organic carbon content of alkalinized soil,and the ability of water and fertilizer conservation in cultivated soil and sustainability of land-use in Hetao Irrigation Area.【Methods】 Taking the lightly alkalinized soil in Hetao Irrigation Area as the research object,five treatments including addition of biochar,addition of cow manure,addition of sheep manure,addition of corn straw and conventional fertilization（control）were set up in the field positioning experiment from 2019 to 2020. The total amount of straw returned to the field in spring was taken as the benchmark,that is,the amount of organic carbon was 2 400 kg/hm². The physicochemical properties and organic carbon density of 0-60 cm soil layer were analyzed.【Results】 Compared with the control group,the pH value of the 0-30 cm soil layer was decreased by 4.4%,the alkalinization degree was decreased by 0.4%,the organic carbon density was increased by 30.9%;and the pH value of 30-60 cm soil layer decreased by 2.3% treated with addition of biochar. Compared with the control group,the available potassium content in 0-30 cm soil layer was increased by 45.2%,the total nitrogen content was increased by 38.0%,the water-stable aggregates larger than 2 mm and 0.25-2 mm were increased by 158.05% and 81.51%,the organic carbon density was increased by 52.4%;and the content of available potassium and available phosphorus in 30-60 cm soil layer was increased by 35.6% and 41.7% respectively treated with addition of cow manure. Compared with the control group,the total nitrogen content in 0-30 cm soil layer was increased by 30.0%,and the water-stable aggregates larger than 2 mm was increased by 357.45%;and the content of available phosphorus in 30-60 cm soil layer was increased by 39.1% treated with addition of sheep manure. Compared with the control group,the water-stable aggregates larger than 2 mm and 0.25-2 mm in 0-30 cm soil layer were increased by 77.62% and 83.01% treated with addition of corn straw.【Conclusion】 Different organic matter had different effects on the physicochemical properties of the slightly alkaliznied soil in Hetao Irrigation Area. The addition of biochar had a good effect on soil salinity and alkalinity improvement. The effect of addition of cow manure and sheep manure on soil physicochemical properties and soil nutrients was better,while the comprehensive effect of applying cow manure on soil physicochemical properties and organic carbon pool was the best,which was conducive to soil water and fertilizer conservation and sustainable production in Hetao Irrigation Area.

Key words: Hetao Irrigation Area, Organic materials, Alkalinized soil, Physicochemical properties, Organic carbon density