The weed flora and seed bank may be influenced by weed management methods, cropping system and crop types. The study aimed at investigating the weed flora composition and weed seed bank characteristics in both arable and tree crops’ fields (Theobroma cacao L. (Cocoa), Cocos nucifera L. (Coconut), Elaeis guineensis Jacq. (Oil palm), Manihot esculenta Crantz. (Cassava), Jatropha curcas L. (Jatropha), and Zea mays L.(Maize). In the arable plots, farmers depended on manual hoe weeding for weed control, while regular slashing and ploughing were adopted for weed management in tree crops fields. The overall weed flora is composed of annual broadleaf (58.10 %), grasses (19.40 %), sedges (6.50 %) and shrubs (16 %) in the entire sampled crop fields. Weed seed bank varied across the soil depths and crop fields. Within 0 – 15 cm soil depth, broadleaf (56.90 %), grass (23.80 %) and sedges (19.0 %) were observed. Deeper soil depth of 16 – 30 cm had 57.2 % (broadleaf), 14.3 % (Grass) and 28.6 % (Sedge) across the sampled plots at eight weeks after weed emergence. Different families of weeds identified varied significantly in frequency across the sampled plots. Differences in weed biomass across the crop fields were a reflection of timing and weed management practices and crop canopy formation (P ≤ 0.05). Plot sown to Oil palm had the highest weed biomass (0.256 kg/m2), with the lowest in Jatropha (0.038 kg/m2). The variations in weed composition and weed seed bank in each sampled plot might have resulted from cultural practices, environmental sieve and allelopathic effects of both crops and weeds.
Keywords: Weed composition, environmental sieve and allelopathy, seed bank
