Effect of sunflower (Helianthus annuus L.) on the suppression of some summer weeds at the Field Station of the University of Zambia

Abstract

Weeds present a major challenge to crop production and need to be controlled. Several methods of weed control exist but they have proved to be less than successful especially in the tropics; therefore new ways of using these methods are still being sought. The use of allelopathy, a form of biological weed control, has been proposed. A systematic screening of 6 sunflower varieties, a crop known to have allelopathic activities was done at the Field Station of the University of Zambia in the 2008/09 and 2009/10 rain-fed growing seasons using a RCBD with 2 maize varieties as the control. Weed diversity was observed, while weed density, weed biomass and crop yield were measured and subjected to analysis of variance. Results showed that although there was a wide diversity of weeds present, 15 were most prevalent. Sunflower varieties, generally, had lower weed density and weed biomass than the control maize varieties. But varietal differences among the sunflower varieties were discerned. The yield reduction was higher in maize grown in a weedy environment than for the sunflowers although here again varietal differences were evident among the sunflowers. It was concluded that the use of sunflower varieties Milika, Record and PAN7352 as an alternative crop can help to reduce weeds in the field.