Knowledge, science, and practice in ecological weed management: farmer–extensionist–scientist interactions - Ecological Management of Agricultural Weeds - page 104

species, the dynamics of weed seed banks, and the physiology of vegetatively
propagated weeds. In many cases, these concepts have been applied princi-
pally for managing herbicides. Weed ecology has also been useful in under-
standing why practices such as rotations, cover crops, and intercropping are
effective in weed management, as other chapters in this topic demonstrate.
Despite the expansion of the off-farm generation of knowledge about weed
management in the past 50-75 years, farmers in temperate and tropical agri-
culture continue to experiment with machinery, crops, cropping systems, and
farm organization for better weed control.
Much of the equipment for reducing herbicide applications, such as band
applicators, wicks, and recirculating sprayers, or for combining spraying with
other operations originated in farm workshops. During the 1970s and early
1980s more than 30% of the entries in the Ideas Competition at the Royal
Norfolk Agricultural Show related to spraying (Sumberg & Okali, 1995, pp.
142-3).
In areas of the world where mechanization is less common, farmers face
different weed problems and experiment with other methods. In Manya
Krobo, a dry forest transition zone in Ghana, farmers in the past 60 years have
gone from cocoa and long fallow cropping to bush fallow food cropping.More
recently they have faced land and labor shortages,less reliable rainfall,and the
spread of new herbaceous and woody weeds (Amanor, 1993). These include
Digitaria and Panicum grasses, Chromolaena odorata , and Leucaena spp. They are
currently experimenting with the conservation of tree seedlings and sprouts
during weeding to reduce the invasion of savanna grasses, the use of cowpea
and short-cycle cassava in different rotations with current crops to maintain
productivity, and selective fallow management to promote native tree and
shrub species.
Contrasting perspectives of farmers, extensionists, and
scientists on weeds
Over the past 50-100 years human society has been formulating and
using knowledge about weeds from different perspectives.These perspectives
represent the views and experience of individuals and groups who have
common or similar experience with weeds and recognize similar rules for pro-
cessing information. In a broader context, these perspectives have been
referred to as knowledge communities (Marglin, 1990; Hess, 1995, pp. 2-4).
Three communities with the strongest interests in weed knowledge are
farmers, extensionists, and scientists, including scientists in both industry