Allelopathy in Nigerian Crop-Weed Systems: Chemical Ecology and Exploitation for Weed Management

This study investigates allelopathic interactions in major Nigerian crop-weed systems, characterising the chemical ecology of allelopathic inhibition and evaluating the potential for exploiting allelopathy as a weed management tool in Nigerian smallholder agriculture. Allelopathy, the inhibition of one plant species by biochemicals released from another, is a natural phenomenon with significant potential for weed management in low-input farming systems. Nigerian crop varieties and indigenous plants harbour allelopathic compounds that have been insufficiently characterised for agronomic exploitation. This study investigates allelopathic potential in aqueous root and shoot extracts of improved and local varieties of sorghum, rice, and cowpea from research sites in Kano, Benue, and Rivers States using standardised bioassay techniques against major weed species. High-performance liquid chromatography is used to characterise the allelochemical profiles of potent extracts. Field experiments test the weed suppression capacity of allelochemically active varieties versus non-allelopathic equivalents in paired plots. Correlation between allelochemical content and field weed suppression intensity is analysed. Findings reveal significant allelopathic variation among sorghum varieties, with local sorghum varieties of northern Nigeria showing higher allelopathic potential than improved varieties due to higher sorgoleone concentrations. Bioassay inhibition rates of 40 to 68 percent against Striga hermonthica seedling germination are demonstrated in vitro. Field experiments show 34 percent reduction in Striga emergence under high-allelopathy sorghum varieties. The study contributes original allelochemical data for Nigerian crop varieties and recommends incorporation of allelopathy testing in variety development programmes.

Keywords: allelopathy, weed management, Striga, sorghum varieties, allelochemicals.