Characteristics of soil water-heat-salt coupling and crop response relationships in saline soils under freezing saline water irrigation.

Frozen saline water irrigation (FSWI) is a method of effectively utilizing saline water to alleviate water scarcity. However, the coupled relationships among water, heat, and salt in soil irrigated with frozen saline water and the key influencing factors of FSWI on crop growth have not been clarified. Here, we conducted two consecutive years of in situ field plot experiments that focused on the freeze-thaw period (FTP) and crop growth period (CGP). The study characterized changes in soil moisture, heat, salinity, and crop growth at different FSWI levels (0, 140, 180, and 220 mm; CK, FSWI ₁₄₀ , FSWI ₁₈₀ , and FSWI ₂₂₀ , respectively). Structural equation modeling (SEM) was performed to reveal the key driving mechanisms and potential environmental factors affecting crop growth under FSWI. The results showed that the FSWI treatment significantly reduced the coefficient of variation (P < 0.05) of temperature (P < 0.05) and cumulative subzero temperature (FSWI ₂₂₀ best) of the deep soil (40-100 cm) during the FTP period, slowed down the accumulation of salts in the tillage soil due to the temperature change, and shortened the duration of the soil freezing and thawing cycle relative to the CK. In addition, secondary drenching during the ablation period promoted downward salt drainage from the till soil (FSWI ₁₈₀ best), which significantly increased (P < 0.05) the till soil water storage in the seedling stage (82%-93%). However, the salt accumulation effect (up to 10.3 kg m ^-2 ) was carried over to the CGP till soil (0-40 cm) when FSWI >180 mm. Moreover, FSWI ₁₈₀ promoted crop growth (seedling emergence, plant height, and stem thickness) and significantly increased yields by 23% (P < 0.05). SEM showed that FSWI promoted the effects of soil water storage, temperature, and salinity on crop yields (0.5 vs -0.14, 0.27 vs 0.12, and -0.38 vs 0.42, respectively) compared with the CK treatment. Soil water storage and soil salinity were the main influencing factors (total effects of 0.92 and -0.38, respectively). In conclusion, FSWI ₁₈₀ is a feasible method of freezing saline water to alleviate water shortage problems in arid areas.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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