In order to explore the reasonable amount of brackish water icing irrigation water and the dynamic migration of soil hydrothermal salt during freezing-thawing period under saline freezing irrigation

taking the severe saline and alkali land as the research object

an in-situ freezing-thawing experiment was carried out in Dalat Banner

Inner Mongolia for two consecutive years

and four irrigation gradients was set

with irrigation amount of 140 mm (S1)

180 mm (S2)

220 mm (S3) and the control (CK) without irrigation

respectively

the salinity of irrigation water was 8~10 g/L.By measuring soil moisture content

soil temperature and salinity distribution during the experimental period

the dynamic migration characteristics of soil hydrothermal salt in saline and alkaline land under saline ice irrigation were analyzed.The results showed that brackish water icing irrigation could significantly increase the soil moisture content after spring ablation

slow down the deep soil temperature variation degree during the freeze-thaw period

reduced the salinity phenomenon caused by soil temperature change

and the larger the irrigation water volume

the greater the increase of soil moisture content and the more significant the thermal insulation effect.After repeated freeze-thaw cycles

soil salinity was reduced under suitable brackish water icing irrigation treatment

and the desalination rate was positively correlated with the irrigation amount when the irrigation water amount was less than 180 mm

and the soil salinity content increased after spring ablation when the irrigation amount was more than 180 mm.During the 2-year experimental period

compared with the control treatment without irrigation

the soil moisture content under the brackish water icing irrigation treatment was increased by 82%~93%;the soil ablation index was increased by 28%~65%;the soil freezing index was reduced by 24%~25%;the desalination rate of 0—40 cm soil layer when the irrigation amount was less than 180 mm could reach up to 59%.Considering the comprehensive consideration

under the premise of not causing soil salt accumulation leading to secondary salinization

soil insulation

moisture preservation and desalination effect under irrigation water of 180 mm is the best

which can provide a suitable soil environment for crop growth in the coming year.