Allelopathic Mechanisms and Agronomic Potential of Aqueous Sorghum Extract as a Sustainable Bioherbicide: A Critical Review

Abstract

Herbicide resistance, environmental contamination, and regulatory constraints increasingly challenge the sustainability of synthetic herbicide–dependent weed management systems. In this context, aqueous sorghum extract (ASE) has emerged as a biologically grounded alternative within integrated weed management (IWM) frameworks. This review synthesizes current evidence on the phytochemical composition, molecular mechanisms, agronomic performance, and translational constraints of ASE as a potential bioherbicide. The bioactivity of ASE is primarily attributed to water-soluble phenolic acids, flavonoids, cyanogenic glycosides, and low-molecular-weight organic acids that collectively impose multi-target physiological stress on susceptible weeds. Mechanistically, ASE interferes with seed germination, hormonal regulation, photosynthetic electron transport, mitochondrial respiration, redox homeostasis, membrane integrity, and protein stability, frequently inducing oxidative stress cascades. Such distributed biochemical interference contrasts with single-site synthetic herbicides and may reduce strong selection pressure for resistance evolution. Laboratory studies report significant inhibition of germination and early seedling growth across monocot and dicot weeds, particularly at concentrations above 10–15% (w/v). However, field-level performance remains inconsistent due to soil adsorption, microbial degradation, environmental instability, and concentration-dependent hormetic responses. Evidence suggests that ASE is most effective as a pre-emergence or early post-emergence suppressive tool and as a complementary component enabling reduced herbicide dosages while maintaining yield stability under moderate weed pressure. Major translational bottlenecks include chemical instability, narrow crop safety margins, lack of standardization, and variability across agroecological contexts. Research priorities include formulation engineering, marker-based standardization, soil–microbiome interaction analysis, and precision deployment. Within diversified IWM systems, ASE offers a promising yet context-dependent strategy for sustainable weed management