Floristic Composition and Phytosociological Structure of Weed Flora Associated with Irrigated Sorghum in the Gezira Scheme, Sudan

Abstract

This study assessed the floristic composition, family dominance, and life-form spectrum of weeds associated with the irrigated Sorghum agro-ecosystem. The study area covered 22,500m2 and was divided into three blocks, each measuring 300x 25 m (700,500m2). A 1x1 m quadrat was used as the sampling unit. And 45 quadrats were randomly laid within each block, giving a total of 90 quadrats across the entire study area. Within each quadrat, all weed species were identified and counted to determine density and frequency. Family composition percentage was also calculated. Species were further classified according to Raunkiaer's life-form system, and the biological spectrum was constructed to assess ecological adaptation strategies.  A total of 27 weed species belonging to 12 families were recorded, indicating moderate floristic diversity under irrigated cultivation conditions. The most dominant families were Fabaceae (22.2%), followed by Poaceae (18.5%), while Asteraceae and Malvaceae each accounted for 14.6 % and Convolvulaceae represented 7.4 %of the total flora. Dicotyledonous species constituted 74.1% of the recorded taxa, whereas monocotyledons represented 25.9 %. Corchorus fascicularis was the most dominant species, showing the highest frequency (77 occurrences) and Density (25.33%). Other dominant species included Hibiscus panduriformis (10.19%), Echinochloa colona (10.12%), and Cynodon dactylon (9.52%). Several species exhibited low densities (<1%), indicating uneven species distribution within the community. Life-form analysis revealed a clear predominance of therophytes (85.2%), with hemiphytes (11.1%) and geophytes (3.7%) occurring at lower frequencies. The dominance of Fabaceae and Poaceae reflects their ecological adaptability, high reproductive capacity, and nutrient –enriched conditions. The high proportion of therophytic species indicates strong adaptation to seasonal disturbance, frequent tillage, and irrigation cycles characteristic of an intensively managed agro-ecosystem.  These findings align with recent studies from sub-Saharan Africa that report similar weed community structures in irrigated cereal systems. The weed flora of irrigated sorghum fields is primarily structured by anthropogenic disturbance, irrigation regimes, and crop management practices. The present study provides baseline floristic and ecological data that are essential for biodiversity monitoring and for designing effective, sustainable weed management strategies in irrigated agriculture systems, particularly within Sudan and comparable agro - ecological regions.