Morphological characterization and population dynamics of Cyperus rotundus L. in vegetable fields of southern Ghana

Abstract

Vegetable production in southern Ghana suffers grave setbacks from purple nutsedge infestation. Several attempts to identify effective and environmentally friendly management methods using the traditional weed research methods have so far not been successful. Hence, this study aimed at designing efficient and environmentally sound management methods by developing an ecological model of the population dynamics of purple nutsedge in vegetable fields. The study comprised three major phases: survey of the agronomic practices and prevalence of the weed in the four agro-ecological zones in the study area, morphological characterization of the weed and the development of an ecological model which was used in determining an appropriate management method. Purple nutsedge was reportedly present on the fields of more than 50 per cent of farmers interviewed and was said to be a problem all year round, especially in the wet season. The weed showed some level of morphological adaptation to agro-ecological conditions in the study area. The major factors which determined differences in purple nutsedge were photosynthetic structures (involucral bracts and leaves), plant height and leaf characteristics. On the whole, differences observed in the morphology of the weed were independent of the agro-ecological zones, despite the adaptations observed. The ecological model reflected purple nutsedge population dynamics at weekly intervals and the yield loss in cabbage (as a test crop) and hence was used to investigate various management options for the weed. It was clear that only an integrated weed management approach could effectively manage purple nutsedge. This approach should include an effective means of reducing the initial viable tuber density of the purple nutsedge.