| In order to investigate the effects of freezing and thawing function on soil salinity distribution and change in cotton field of saline-alkaline soils with drip irrigation under plastic film under snow cover condition in North Xinjiang, using the spatial and temporal variation method, taking the soil salinity change at early spring in 6 cotton fields with 0, 4, 6, 8, 10 and 15 year continued drip irrigation under plastic film as case study, carried out the analysis. The results showed that: The stagnant water in frozen layer and infiltration of snow thawing had the natural leaching function for the soil salinity in 80～100 cm soil depth. Before and after freezing and thawing, the soil salinity distribution displayed a wide-mouth-cup shape. Under the influence of water movement during April 5 to April 14, the soil salinity was reduced at 60～80 cm soil layers, among them, a part of water went up by capillary through evaporation, stranded at 0～40 cm soil depth. Another part of water leached down by gravity, the soil salinity content was increased below 80 cm depth. The amount of salt storage was 29 063.00 g in 0～140 cm soil depth in 0 a land, but after drip irrigation for 15 years, reduced to 5 778.86 g. The leaching function on soil salinity by freeze-thaw was relatively obvious in shorter years of drip irrigation, as the higher soil salinity content, the more notable for the leaching function. The salt storage content was reduced 8 941.33 g in 0～140 cm soil depth in 0 a drip irrigation cotton land after freeze-thaw. After 15 years of drip irrigation, the cotton land was reduced 614.62 g. So put forward the natural leaching function by freeze-thaw cycles on soil salinity was one of the important factors for reducing soil salinity content in cotton land by long-term drip irrigation in Northern Xinjiang. |