Alfalfa-mediated phytoremediation and soil restoration for sustainable cereal and fruit crop production: a review of roles, detoxification mechanisms, nitrogen enhancement, and agroecological integration

Abstract

Soil contamination by heavy metals, petroleum hydrocarbons, and excessive agrochemical inputs, coupled with declining soil fertility, poses a major threat to sustainable cereal and fruit production and global food security. This review synthesizes evidence from peer-reviewed studies published between 2000 and 2026 to evaluate the multifunctional role of alfalfa ( Medicago sativa L.) as a biological soil engineer for phytoremediation, soil restoration, and sustainable agricultural intensification. The reviewed evidence indicates that alfalfa can contribute to the remediation of contaminated soils through phytoextraction, phytostabilization, and rhizosphere-mediated degradation of organic pollutants, while simultaneously improving soil fertility through biological nitrogen fixation (BNF). Its deep and extensive root system can enhance soil structure, aggregation, water-holding capacity, and soil organic carbon, while promoting beneficial microbial communities, nutrient cycling, and suppression of soil-borne pathogens. In cereal-based systems, these processes may reduce contaminant bioavailability, decrease dependence on synthetic fertilizers, and improve the productivity and resilience of subsequent crops. In fruit-based systems, including orchards and perennial cropping systems, alfalfa can provide additional benefits through intercropping or cover-cropping, including nitrogen inputs, improved soil moisture conservation, enhanced soil biological activity, and potential economic returns. However, the accumulation of contaminants in alfalfa biomass remains an important food- and feed-safety concern, highlighting the need for rigorous contaminant monitoring and appropriate biomass management. Emerging approaches, including targeted microbial inoculation, biochar amendments, intercropping strategies, and gene-editing technologies, may further improve remediation efficiency and agroecosystem sustainability. Overall, integrating alfalfa into cereal- and fruit-based production systems represents a promising nature-based approach for restoring degraded soils, improving soil resilience, reducing external inputs, and supporting sustainable crop production. Future research should prioritize long-term, multi-site field studies to evaluate remediation performance, contaminant mass balances, plant–microbe interactions, biomass safety, and the long-term productivity of cereal and fruit production systems.