Biochar and nanoparticle composites (nano-modified biochar) as next-generation soil amendments for sustainable salt stress management.
BACKGROUND Soil salinity is one of the most critical abiotic stressors limiting global agricultural productivity by adversely affecting plant physiology, nutrient dynamics and soil health. Excessive accumulation of soluble salts disrupts osmotic balance, induces ionic toxicity and elevates oxidative stress, thereby impairing plant metabolism and soil ecological stability. In recent years, biochar and engineered nanoparticles (NPs) have emerged as innovative and sustainable soil amendments capable of mitigating salinity-induced deterioration in agroecosystems. Biochar improves soil structure, water retention and cation exchange capacity while promoting microbial activity and nutrient availability. In contrast, nanoparticles enhance stress tolerance by regulating redox balance, improving nutrient use efficiency and modulating antioxidant defense systems. AIM OF REVIEW The review aims to critically evaluate the individual and combine role of biochar and nanoparticles as a nano-modified biochar (NP-BC) in alleviating salinity stress in plant-soil systems. The review further explores the mechanistic pathways through which NP-BC improves plant physiological performance, soil biochemical properties and stress resilience under saline conditions and highlight their potential as sustainable tools for managing saline agroecosystems. KEY SCIENTIFIC CONCEPTS OF THE REVIEW The integration of biochar with nanoparticles as NP-BC offers a multifunctional approach combining structural, chemical and catalytic properties. This combined system improves ion homeostasis through Na⁺ exclusion and K⁺ retention, enhances osmotic regulation, strengthens antioxidant defense systems, supports soil microbial activity and nutrient cycling under saline conditions. The review provides a comprehensive synthesis of the mechanistic interactions and functional roles of biochar, nanoparticles and NP-BC in mitigating salt stress. Furthermore, it highlights key research gaps related to dosage optimization, long-term environmental implications and field-scale applicability to support the development of next-generation sustainable nano-enabled soil management strategies.