Associations among texture, bulk density and soil moisture during post-mining soil recovery in semi-arid conditions

Post-mining phosphorite landscapes in semi-arid regions often retain physical constraints that limit vegetation establishment and slow soil recovery. We assessed soil physical recovery at the Zhanatas phosphorite deposit (southern Kazakhstan) by comparing three site types: (i) a reclaimed dump (technical reclamation in 2012, biological reclamation in 2013; ~2 ha; ~50 cm loam substrate; 70–75% plant establishment), (ii) a dump undergoing passive selfrecovery since mine closure in 1984 with sparse vegetation cover (~9.5–10%), and (iii) an undisturbed reference soil. During May–September 2025, three soil profiles were excavated per site and sampled by genetic horizons. Across sites, materials were sand-dominated, but the fine fraction (<0.01 mm) differed strongly among recovery pathways. The reclaimed site showed stable near-surface texture (<0.01 mm = 31.97–34.93% at 0–40 cm), comparable to the upper horizons of the naturally revegetated dump (28.60–30.34% at 0–70 cm). In contrast, a deep layer of the naturally revegetated dump (70–110 cm) was extremely coarse (sand 89.89%; <0.01 mm 8.87%), indicating a persistent textural discontinuity. The undisturbed soil had the highest fine fraction (<0.01 mm = 34.57–45.05%). Moisture ranged from 2.09% (reclaimed 0–10 cm) to 11.69% (dump 70–110 cm). PCA differentiated site types and revealed the greatest heterogeneity in the naturally recovering dump. Reclamation improved near-surface physical conditions, but full convergence to reference soil remains incomplete due to strong textural contrasts within the profile.

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