Science and Education Publishing World Journal of Agricultural Research 1 1 2013 07 26 Allelopathic Effect of some Weeds on the Germination of Seeds of Selected Crops Grown in Akwa Ibom State, Nigeria 59 64 EN P.E. Usuah G. N. Udom I.D. Edem . Department of Soil Science and Land Resources Management, University of Uyo, Uyo, Nigeria WJAR2013143 10.12691/wjar-1-4-3 2013 06 08 2013 07 23 2013 07 26 The allelopathic potentials of six dominant weeds at the Teaching and Research Farm 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 shoots 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 shoots 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 Chromolaenaodorata.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.