Biosolids application enhances the growth of Aloe vera plants and provides a sustainable practice for nutrient recirculation in agricultural soils

In the present study, the fertilization potential of biosolids (sewage sludge; SS) for the cultivation of Aloe vera plants was investigated using block design. Pot experiments were conducted in this study using 50, 100, 150, and 200 g/kg of SS. Results showed that SS-fertilized soils significantly (p < 0.05) affected the proximate, biochemical, and heavy metal parameters of A. vera plants. In particular, the T4 treatment gave the best results with maximum plant height 62.21 ± 0.10 cm, number of leaves per plant 18.00 ± 4.00, shoot-to-root ratio 6:1, fresh weight 1972.10 ± 0.07 g per plant, dry weight 175.49 ± 0.15 g per plant, total chlorophyll content (TCC) 0.41 ± 0.02 mg/g fwt., carotenoids 0.25 ± 0.04 mg/g, total flavonoids 7.55 ± 0.05 mg/g, total tannins 3.87 ± 0.06 µg/g, ascorbic acid 532.14 ± 0.10 µg/g, superoxide dismutase (SOD) 46.28 ± 0.19 µg/g, catalase (CAT) 119.23 ± 0.17 µg/g, salicylic acid 3.05 ± 0.12 mg/ml and anthraquinones 0.45 ± 0.04 mg/ml, respectively. The proximate plant characteristics were 96.25 ± 2.71% moisture content, crude protein 0.93 ± 0.05%, crude fiber 5.78 ± 0.44%, crude lipid 3.25 ± 0.02%, lignin 10.74 ± 0.30%, cellulose 13.56 ± 1.06%, hemicellulose 7.24 ± 0.14%, ash 8.75 ± 0.03%, and carbohydrate contents 52.18 ± 1.10% in comparison with control treatment. The bioaccumulation factor showed that heavy metal accumulation was in the order of Cd < Ni < Cu < Pb < Cr < Zn < Fe. The prediction models developed on the basis of soil properties showed good fitness results for the prediction of heavy metal uptake by A. vera plants. The study presented a sustainable approach for managing SS in an eco-friendly way while producing good-quality A. vera plants.