The Botswana Journal of Agriculture and Applied Sciences is published in English twice in a year, January and July. It publishes original research in all areas of agriculture and its related applied sciences. Submission of a manuscript indicates that it has not, and will not without the consent of the Editor-in-Chief, be published elsewhere. Manuscript inclusive of illustrations and tables should be sent by email to: Editor-in-Chief, Botswana College of Agriculture, Private Bag 0027,Gaborone, Botswana. Prof O R Madibela omadibel@bca.bw Manuscript will be reviewed but the authors have total responsibility of the factual accuracy of their papers. For every published paper in this journal, the author(s) will get ten free reprints; more can be ordered at a cost from the publisher.