Knowledge, science, and practice in ecological weed management: farmer–extensionist–scientist interactions - Ecological Management of Agricultural Weeds - page 112

The Nicaraguan Coffee Growers' Union (UNICAFE, 1998) found that coffee
yields could double with improved management and on better sites could
quadruple with higher inputs and better management. During recent years,
pesticide poisonings and the expenditure of foreign currency for herbicide
imports have also fluctuated, although the fluctuations have not been corre-
lated with crop yields (Beck, 1997).
These efforts in temperate and tropical regions to improve methods of crop
production,including weed control,point to an important and still unfolding
lesson. Progress has been possible, but not without costs and failures. Further
progress will depend on the ability of scientists, extensionists, and farmers to
work within increasingly complex expectations.At one time the objective was
simply higher crop yields.Current goals include higher crop yields,protection
of human health and the environment, improvement of soil and water
quality, and greater market competitiveness. These factors are represented on
the horizontal axis in Figure 3.2 as the increasing ecological, social, and eco-
nomic complexity affecting crop production. In the case of weed manage-
ment, this complexity is a product of several factors: changes in the larger
social and economic context of agriculture,increasing understanding of weed
ecology and crop production, and a need to ameliorate past negative results,
such as herbicide resistance, and minimize them in the future.
In confronting this complexity, weed management has progressed from
initially simple input-output research (e.g.,trials on herbicide rates and cover
crop species) through site-specific recommendations (e.g., herbicide rates by
soil types) and problem-solving research (e.g., limiting competition between
crops and cover crops) to predictive models and decision aids (e.g., Kropff &
van Laar, 1993; Forcella et al ., 1996). On one hand, these changes can be inter-
preted as the successive fine tuning of recommendations for broadscale,
uniform weed management.This possibility for the vertical axis in Figure 3.2
originates from the perspective that the natural world can be increasingly pre-
dicted and controlled. However, these advances can also be seen as first steps
in the development of adaptive management (Holling,1978,pp.1-21; Roling
& Wagemakers, 1998). In conventional modern agriculture, most research
aims to provide farmers with general technologies and recommendations
suited for average situations.In contrast,the aim of adaptive management is a
progressive increase in farmers' ability to develop and adapt a range of tech-
nologies for a local fit under variable and uncertain situations.Adaptive man-
agement assumes that decisions on weed control are based on less than perfect
information,that control measures are not completely effective,and that each
crop season provides additional data for the farmer on the development of
more effective weed management. This is an appropriate response to the