P.E. Usuah¹, G. N. Udom², I.D. Edem^1,

The allelopathic potentials of six dominant weeds at the Teaching and Research Farms of the Akwa Ibom State University and adjoining areas, often used for mulching and green manuring, were evaluated on the germination of the seeds of six commonly grown crops of the region. Extracts from 500g of finely chopped tops and roots each of Aspilia africana (Pers) C. D. Adams, Emilia sonchifolia (L) DC, Crotalaria retusa L, Chromolaena odorata (L) King & Robinson, Panicum maximum L., and Cyperus esculentus L., were obtained with one litre of distilled water. These were applied to seeds of Zea mays L., Citrullus lanatus Thunb, Abelmoschus esculentus (L) Moench, Vigna unguiculata (L) Walp, Glycine max (L) Merr, and Arachis hypogaea L. in petri dishes. The equivalence of 0, 2.0, 4.0, 8.0 and 12.0 Mg ha^-1 of finely chopped fresh tops of each weed were also applied to 1.0kg of heat-sterilized soil in planting polybags as mulches. Water extracts of the weeds (shoots and roots) reduced germination counts of the seeds by 10 to 100%. Cyperus esculentus L.shoots extracts was the most phytotoxic, followed by Panicum maximum L and Chromolaena odorata. The decomposing mulches showed varied but less inhibitory effects on the seeds with a trend toward increasing inhibitory power with increasing mulch level and decreasing seed size. The results revealed that a possible relationship between the low seed germination and poor seedling growths often observed in the area. However, further studies are needed to confirm the findings.

allelopathy, local weeds, decomposing mulches, seed germination, southeastern Nigeria.