Soil water and salt transfer are important processes under freezing-thawing conditions in nature. The effects of soil salt concentration on soil water and heat transfer have not been investigated thoroughly under freezing/thawing conditions. The freeze-thaw characteristics of salinized soil and thecorresponding control mechanism of water-heat-salt after the mulched autumn irrigation in cold-drought-salt irrigation district were explored in the study. The field freez-thaw- experiment was conducted on the salinized soil after the mulched autumn irrigation with 5 treatments in terms of straw mulching quantity of 1.2 kg/m2 (F1.2)

0.9 kg/m2 (F0.9)

0.6 kg/m2 (F0.6)

0.3 kg/m2 (F0.3) and nomulching (CK). Results showed that: straw mulch promoted process of soil freeze-thaw

and changed the relationship between soil temperature and air temperature

resulting in the redistribution of water and salt in soil profiles

especially in the surface soil and tillage layer

which enhanced the available amount of spring water in the next year and restrained the spring salinification in surface soil and tillage layer

thus

the quality of autumn irrigation was improved. The maximum freezing depth of mulching was 4~26 cm smaller than CK

the initial freezing time and thawing time are lagged by 0~12 d and 0~21 d. The vaporization of melting water was restrained due to the straw mulch

which resulted weak surface salt accumulation. After the thawing period

the soil moisture content in F0.9 was the largest one in soil depth of 0~10 cm

and the F1.2 related ratio of desalinization was 81.18%

which was the best one among all the treatments. As for the tillage layer of 0~40 cm

the soil moisture content of F0.9 was the highest one and the best one desalinization occurred in F0.6

which was 75.65%. In order to ensure the appropriate salt content and water content in the coming year

the coverage amount of 0.6~0.9 kg/m2 is the optimal one. The findings can be used to provide references for the optimization of autumn irrigation system in Hetao Irrigation District.