____________________________________________________________________________________________ *Corresponding author: Email: ueudensi@yahoo.co.uk, udensi.udensi@uniport.edu.ng; American Journal of Experimental Agriculture 3(4): 767-779, 2013 SCIENCEDOMAIN international www.sciencedomain.org Evaluation of Pre-Emergence Herbicides for Weed Control in Cowpea (Vigna unguiculata (L.) Walp.) in a Forest - Savanna Transition Zone Omovbude Sunday 1 and Udensi Ekea Udensi 1* 1 Department of Crop and Soil Science, University of Port Harcourt, East-West Road, Choba P.M.B 5323 Port Harcourt, Nigeria. Authors’ contributions This work was carried out in collaboration between the authors. Author OS designed the study, performed the statistical analysis, wrote the protocol, and the first draft of the manuscript. Author UEU assisted in the organization of the data, reviewed the manuscript and literature, designed the economic analyses of the study and prepared the manuscript for publication. Authors read and approved the final manuscript. Received 20 th March 2013 Accepted 3 rd May 2013 Published 1 st June 2013 ABSTRACT Aims: To evaluate the efficacy and economic benefits of selected pre-emergence herbicides for weed control in cowpea. Study Design: Randomized complete block design with four replications was used. Place and Duration of Study: Research and Teaching Farm of Ambrose Alli University in Ekpoma (Lat. 6 º 45’N, Long. 6 º 8’E), in a forest-savanna transition zone of Nigeria, between August and December 2005 and August and December 2006. Methodology: Five weed control treatments evaluated against unweeded control were; Codal gold (R) (250g prometryne + 162.5 g metolachlor per litre) at a rate of 1.65 kg a.i ha -1 , Galex (R) (Metolachlor 250g + metobromuron 250g per litre) at the rate of 3.0 kg a.1.ha -1 ; Pendilin (R) (Pendimethalin 500g per litre) at a rate of 2.0 kg a.i ha -1 , one hoe – weeding at 3 weeks after planting (WAP) and two hoe weeding at 3 and 7 WAP. Results: Herbicides treatments and hoe weeded twice gave an acceptable (≥70%) weed control in both years. Cowpea yield was best under Codal gold at 1.65 kg a.i ha -1 (with an average yield of ≥ 1600kg ha -1 ) while the unweeded control had the poorest yield (between 800 and 900 kg ha -1 ) in both years. The highest profit was obtained under Codal gold at 1.65 kg a.i ha -1 and the lowest in plot hoe weeded twice. The highest cost benefit ratio Research Article