Effects of diatomite (DE) application on physical properties of soils subjected to freeze-thaw cycles

• DE application decreased BD of soils subjected to the same number of FT cycles.
• Effects of FT on AS showed changes depending on soil type and amount of DE applied.
• Increase of DE application rate reduced the negative effect of FT cycles on AS.
• Effectiveness of DE increased with the increases in the application doses.

Freezing and thawing (FT) is a natural and inevitable process and has great importance on the physical, chemical, and biological properties of soil. Protecting the soil structure from the detrimental effects of FT is of great importance for soil conservation. Use of diatomite (DE) as a soil amendment is new and no attention has been given to the potential effect of DE on soil properties modified by the freezing-thawing process. Therefore, this study was conducted to determine the possible effects of DE applications (0, 10, 20, and 30% volume/volume) on the bulk density (BD), aggregate stability (AS) and saturated hydraulic conductivity (ks) of soils with different textures subjected to different numbers of freeze-thaw cycles. Application of diatomite decreased BD of soils subjected to the same number of freeze-thaw cycles. As compared to the control (0% DE) of the same number of freeze-thaw cycles, the decreasing rates in BD values at 30% DE application dose were 10.7, 6.1, 9.1 and 9.7% for 0, 3, 6 and 9 cycles of Soil I, respectively. These values were 8.2, 6.4, 7.2 and 3.3% for Soil II and 4.2, 7.1, 2.0 and 7.7% for Soil III. Diatomite applications significantly increased AS of all soils. Correlation coefficients between DE application and AS were found as 0.743**, 0.725** and 0.737** for Soil I, II and III, respectively. Effects of experimental factor freeze-thaw on aggregate stability showed differences depending on soil type and amount of DE applied. Correlation coefficients between AS and FT cycles were found as −0.372**, −0.571** and −0.079 for Soil I, II and III, respectively. The increase of DE rate reduced the negative effect of freeze-thaw on aggregate stability of all soils subjected to same number of FT cycles, as compared to the controls. Diatomite applications significantly decreased the hydraulic conductivity, probably due to the increase of colloidal fraction and clogging of macropores. Results obtained have shown that DE application not only decreased the bulk density, but also improved the aggregate stability of soils subjected to the same number of freeze-thaw cycles.