Fly ash-mediated changes in soil properties regulate nutrient dynamics, plant growth, and stress responses in Tribulus terrestris L

Fly ash (FA) is considered as a waste because it is a by-product of thermal power plants. Fly ash has attracted considerable research attention as a soil amendment, yet its combined influence on soil physicochemical properties, nutrient dynamics, and stress responses in medicinal plants has received far less scrutiny. The present study reported the impact of FA amended soil on physicochemical and biochemical responses on Tribulus terrestris L., which is a medicinal plant. A 90-day-controlled pot experiment has been done in which different doses of FA were mixed with soil (T0 to T5: T0 (0% FA), T1 (20% FA), T2 (30% FA), T3 (40% FA), T4 (50% FA), and T5 (100% FA), with the remaining proportion consisting of garden soil (v/v)). The elemental analysis of base material (fly ash or fly ash amended soil), different soil properties and biochemical analysis of plants were done. One-way ANOVA confirmed significant effects of fly ash treatment on the measured soil physicochemical properties, biochemical parameters, and photosynthetic pigments ( p < 0.05). Tukey’s HSD post-hoc analysis further identified significant differences among treatment means, with the strongest responses generally observed at intermediate fly ash levels, particularly T3 (40%FA), whereas responses declined at the highest application level (T5, 100%FA). Fly ash amendment altered soil physicochemical properties, including increased water-holding capacity and electrical conductivity, reduced bulk density and pH, and increased concentrations of several micronutrients. The correlation analysis was done in between apparently decreased percent elemental concentrations and plant growth responses. The availability of micronutrients displayed positive correlation; however, only selected relationships exceeded the threshold for statistical significance. Pearson’s correlation analysis demonstrated the strongest positive correlations between proline and Zn, Cu, Mn, Ni, Fe and Mg, while moderate positive correlations were observed between Mg and protein, nitrogen, and sugar. The higher concentrations of FA amended soil inhibited the growth of plants (T4 and T5). The results show that fly ash modification helps to improve soil physicochemical properties and enable Tribulus terrestris L. physiological performance under regulated pot circumstances. The findings indicate that fly ash amendment can modify soil properties and plant responses under controlled pot conditions; however, longer-term field studies, plant-tissue metal assessment, and environmental and safety evaluations are required before recommending fly ash for medicinal plant cultivation.