Phytochemical Adaptation and Growth Performance of Guizotia abyssinica in Coal Mining Overburden Soil for Ecological Restoration

Open‐cast coal mining causes severe soil degradation, leading to loss of fertility and ecological imbalance. This study aimed to rehabilitate coal mine‐degraded land by mixing garden soil with overburden (OB) soil and evaluating the growth, soil improvement, and phytochemical responses of Guizotia abyssinica (niger seed) as a pioneer species for reclamation. A pot experiment was conducted by mixing OB soil from coal mines and garden soil mixtures at different mixing ratios. T0 (100G:0OB), T1 (75G:25 OB), T2 (50G:50 OB), T3 (25G:75 OB), and T4 (0G:100OB), maintaining 5 kg per pot. The pots were cultivated with G. abyssinica for 120 days under controlled conditions. Guizotia abyssinica is a medicinal plant that contains phytochemicals and antioxidant potential. The cultivation of Guizotia abyssinica significantly improved soil chemical properties along the soil‐OB gradient, and the improvement was most pronounced in the OB‐dominated treatment. Guizotia abyssinica reduced the concentrations of heavy metals (Fe, Mn, Pb, Cu, Zn) in soil. The heavy metal content in the soil decreased, and the extent of the decrease varied by treatment. The highest decrease in heavy metal content was observed in T4, followed by T3. The phytochemical response was highest in T2, where maximum phenolics (55.0 ± 1.7 mg GAE g − 1 ), flavonoids (23.0 ± 1.1 mg QE g − 1 ), tannins (16.2 ± 0.8 mg TAE g − 1 ), and DPPH (63.0 ± 2.0 mg AAE g − 1 ) were recorded and the amount of chlorophyll decreased from 2.46 ± 0.08 in T0 to 1.95 ± 0.06 in T2 and 1.10 ± 0.05 in T4. The blending of ≤ 50% coal mine spoil with garden soils was found to be effective in enhancing soil fertility, reducing the mobility of metals, and enhancing antioxidant metabolism in G. abyssinica . Principal component analysis (PCA) and correlation analysis indicated an inverse relationship between heavy metal concentrations and pigment contents, while antioxidant compounds showed adaptive responses under stress conditions. It shows that G. abyssinica not only reduces metal toxicity but also helps to stabilize soil fertility. The present study indicates that G. abyssinica is a promising candidate for the initial stages of ecological restoration in coal mine‐degraded lands.