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.
