Foliar use of TiO2-nanoparticles for okra (Abelmoschus esculentus L. Moench) cultivation on sewage sludge–amended soils. biochemical response and heavy metal accumulation

Abstract

Considering its richness in organic and inorganic mineral nutrients, the recycling of sewage sludge (SS) is highly considered as a soil supplement in agriculture. However, the fate of hazardous heavy metal accumulation in the crops cultivated in SS amended soils is always a source of concern. Since nanoparticles are widely recognized to reduce heavy metal uptake by crop plants; thus, the present experiment deals with okra (Abelmoschus esculentus L. Moench) cultivation under the combined application of SS and TiO2-nanoparticles (NPs). Triplicated pot experiments were conducted using different doses of SS and TiO2-NPs such as 0 g/kg SS (control), 50 g/kg SS, 50 g/kg SS + TiO2, 100 g/kg SS, and 100 g/kg SS + TiO2, respectively. The findings of this study indicated that among the doses of treatment combinations investigated, 100 g/kg SS + TiO2 showed a significant (p < 0.05) increase in the okra plant yield (287.87 ± 4.06 g/plant) and other biochemical parameters such as fruit length (13.97 ± 0.54 cm), plant height (75.05 ± 3.18 cm), superoxide dismutase (SOD: 110.68 ± 3.11 μ/mg), catalase (CAT: 81.32 ± 3.52 μ/mg), and chlorophyll content (3.12 ± 0.05 mg/g fwt.). Also, the maximum contents of six heavy metals in the soil and cultivated okra plant tissues (fruit, stem, and root regions) followed the order of Fe > Mn > Cu > Zn > Cr > Cd using the same treatment. Bioaccumulation and health risk assessment indicated that foliar application of TiO2-NPs significantly reduced the fate of heavy metal accumulation under higher doses of SS application. Therefore, the findings of this study suggested that the combined use of SS and TiO2-NPs may be useful in ameliorating the negative consequences of heavy metal accumulation in cultivated okra crops.