Conclusions
We evaluated the dynamic changes in SWC and ST during freeze-thawing in
agricultural soils. During the study period, the freezing point and
water migration as well as the distribution of SWC changed
significantly. The initial SWC distribution seemed to control the upward
water movement. The lowest ST was -18.92℃ and occurred at depths above
20 cm, while the highest SWC (19.79%) occurred at a depth of 80-100 cm.
During freezing, the temperature affected the freezing front, resulting
in a more rapid thawing process compared to the freezing process. Before
the ST dropped to the freezing point, upward soil water migration caused
a slight decrease in SWC in each layer. In general, freeze-thawing is
affected by changes in water potential energy and pore pressure
gradient, resulting in the migration of soil water to the upper layers.
In addition, during the entire freezing process, the upper soil (0-60
cm) was significantly affected by temperature changes, and its ST levels
and water content fluctuations were significantly stronger. Affected by
freeze-thawing, the soil texture and physical properties will be greatly
changed, the soil compaction will be reduced, and the soil particles
will be more broken. This, in turn, increases wind erosion and the
frequency of dust events in semi-arid agricultural areas, which might
also alter carbon and nitrogen cycles. Soil thawing increased soil water
storage in farmland, reducing reliance on irrigation. Our results
provide a deeper understanding of soil freeze-thawing processes in
semi-arid agricultural areas and their impacts on crops, facilitating
the development of adequate management strategies.