Ecological Restoration of Degraded Mining Soils Through Key‐Layer Construction Using Industrial By‐Products: A Comprehensive Analysis of Soil Physics, Microbiology, and Maize Yield

ABSTRACT

Coal mining severely degrades soil profiles and ecosystem functions, highlighting the need for effective reclamation. Reconstructing soil profiles with industrial solid wastes offers a promising waste‐to‐resource approach, but the ecological effects of different engineered key‐layer materials remain unclear. We established four field‐scale simulation treatments in a semiarid mining area: a homogeneous loess control (T1), a conventional coal‐gangue reconstruction treatment (T2), a fly‐ash key‐layer treatment (T3), and a magnesia‐sludge key‐layer treatment (T4). The three reconstructed profiles consisted of 0–40 cm loess, a 40–70 cm key layer, and 70–200 cm coarse coal gangue. T3 markedly improved water retention, with soil water content at 60 cm nearly twice that of T2 in June (0.100 vs. 0.050 m ³  m ⁻³ ) and August (0.093 vs. 0.046 m ³  m ⁻³ ). However, the chemical and biological responses differed among materials. T4 showed markedly elevated EC at 60 cm, reaching 6.595 and 6.540 dS m ⁻¹ in June and August, respectively. By contrast, T3 maintained a more balanced water–salt regime, promoted surface nutrient enrichment, and supported relatively high microbial diversity. Maize yield in T3 was 11.1% and 9.0% higher than in T2 and T4, respectively. Partial least squares path modeling revealed interconnected associations among soil physical conditions, soil chemical properties, microbial communities, and maize yield. The negative path from soil physical to soil chemical properties (path coefficient = −0.662, p  = 0.003) may reflect incomplete coordination between physical improvement and nutrient replenishment during early reconstruction. Fungal communities were strongly and positively associated with maize yield (path coefficient = 0.777, p  < 0.001). Overall, fly ash performed best among the reconstructed treatments and showed considerable potential for improving soil function and agricultural productivity in degraded semiarid mine lands.