Allelopathy in Sustainable Weed Management: From Chemical Interference to Field-scale Integration

Abstract

Allelopathy has long been proposed as a biological route to reduce reliance on synthetic herbicides, yet the agricultural evidence is more conditional than the frequency of laboratory phytotoxicity reports suggests. This critical narrative review evaluates allelopathy as a component of sustainable weed management by integrating evidence on allelochemical production, release and fate; crop–weed interference; breeding and phenotyping; cover crops and residues; plant extracts and natural-product herbicide discovery; and field-scale implementation. Literature was considered through 6 July 2026, with emphasis on peer-reviewed studies that linked biological effects to plausible chemical mechanisms and agronomic outcomes. The evidence is strongest for well-characterised chemical systems such as momilactones in rice, sorgoleone in sorghum, and benzoxazinoids in rye and wheat. Even in these systems, however, chemically mediated inhibition in the rhizosphere is difficult to separate from resource competition, canopy effects, residue-mediated physical suppression and microbial transformation. Field studies of weed-suppressive cultivars and cover crops demonstrate practically useful suppression, but they often establish an interference phenotype rather than allelopathic causality. Plant extracts and formulated allelochemicals provide credible leads for reduced-herbicide programmes and bioherbicide development, although dose realism, stability, selectivity, formulation, non-target effects and economic performance remain major translational constraints. The most defensible role for allelopathy is therefore not as a universal replacement for herbicides but as one ecological and biochemical hurdle within diversified integrated weed management. Future progress depends on field experiments that combine genetic contrasts, chemical quantification, spatial rhizosphere measurements, competition controls, microbiome-aware fate analysis and multi-environment agronomic validation. Such evidence would allow allelopathy to move from recurrent proof-of-concept towards reproducible, selective and economically credible weed-management functions.