Effects of engineered nanoparticles on rhizospheric organisms: A critical evaluation and future perspective

Modern agricultural technologies increasingly employ engineered nanoparticles (ENPs) to enhance crop production, stress resistance, and fertilizer utilization. However, their integration into the soil systems occurs within the dynamic rhizosphere under the active participation of plants, bacteria and soil animals in interrelated trophic and biogeochemical networks. This review offers a comprehensive study on the ecological activities of metal and metal-oxide ENPs in relation to changes in rhizosphere architecture and functionality. It analyses their effects on microbial community dynamics, soil fauna interactions, nitrogen cycle and trophic transfer mechanisms. It deals with the physicochemical properties of ENPs such as size, surface chemistry, dissolving behaviour, redox activity and their transformation, bioavailability, and ecological identity in heterogeneous soil. An emphasis is placed on ENP-induced modification in bacterial and fungal diversity, reconfiguration of functional guilds (saprotrophs, symbiotrophs and pathogens), modulation of root exudation and signalling mechanisms. These modifications therefore influence soil enzyme activities and carbon-nitrogen mineralization. This study provides evidence that ENPs are absorbed and bioaccumulated inside soil food webs, where they might be trophically amplified and attenuated. This work unravels sublethal but ecologically meaningful influences on soil fauna behaviour as well as ecosystem feedback loops. By combining these techniques from several mechanistic scales, this study presents a conceptual framework for sustainable nano-agroecology to balance agronomic benefits with soil health and biodiversity conservation in the longer term. Briefly, the results depict the significance of a context-specific, benign-by-design ENPs approach for sustainable and environmentally friendly agricultural production.