Objective Exploring the salt washing effect of deep loosening and barrier-breaking on heavy saline soil with clay interlayer.

Methods The heavy sulfate-chloride saline-alkali cultivated land was taken as the research object and the physical soil structure method of mechanical deep loosening was adopted to break the obstacle layers at different depths, thereby realizing flood irrigation for salt washing.

Results The overall change in pH before and after irrigation was not obvious. The total salt reduction on the surface of the deep loosening area was 79.63%, while that in the non-deep loosening area was 43.68%. This indicated that deep loosening and obstacle-breaking helped the soil salts to be irrigated from top to bottom to the lower layer and significantly reduced the salt content on the soil surface. Deep loosening and barrier-breaking could effectively promote the irrigation of Cl⁻, Na⁺, Ca²⁺, K⁺, Mg²⁺ and other ions to the lower layer, but had little impact on SO₄²⁻ at the depths of 0～−20 and −80～−100 cm. After deep loosening, SO₄²⁻ at the depths of −20～−40 and −40～−60 cm was leached to the lower layer, and at the same time, the salt type at the depth of −40～−80 cm was changed, turning sulfate saline soil into chloride-sulfate saline soil. Except that the desalination rate of the soil layer at −20～−40 cm was less than 0%, the desalination rates of the other soil layers in the deep loosening area were significantly higher than those in the non-deep loosening area, with an increase range of 27.69%～35.53%.

Conclusion Deep loosening and obstacle-breaking can significantly improve the leaching of soil salts in the deep loosening area, reduce the salt content on the surface layer, and increase the desalination rate.