Agriculture Reference
In-Depth Information
Obstacles and opportunities in the use of crop
diversification for weed management
This chapter has presented many examples of how crop rotation,
intercropping, and agroforestry practices improve crop production and weed
management. Despite the advantages offered by crop diversification, the
trend in many industrialized nations and a growing number of developing
nations is toward greater specialization and less crop diversity. Specialization
in only one or two crops on a farm can lead to greater economies of scale, but
attendant costs should not be ignored. Compared with more diversified
systems,weed management in simplified cropping systems generally requires
either more manual labor, more frequent use of mechanical control tactics, or
greater quantities of herbicides.
How can crop diversification be better used to improve crop production
and weed management? The first challenge is philosophical: agricultural
practitioners and scientists must recognize the importance of ecology as well
as technology in managing weeds. Successful management of weeds in multi-
component cropping systems is a sophisticated activity that requires compre-
hensive knowledge of competitive and facilitative interactions, and factors
that mediate those interactions. Applied community ecology must have as
much importance and intellectual status as the discovery,synthesis,and use of
herbicides.
A second challenge is scientific: crop rotation, intercropping, and agrofo-
restry systems can promote crop performance and suppress weed germina-
tion, establishment, growth, competitive ability, and reproduction. However,
information on the relevant mechanisms is inadequate. How can crop rota-
tion be used to manipulate soil conditions so as to stimulate crop root growth
while increasing weed seed mortality? What types of diversity within crop
sequences best suppress particular species of weeds? What are the best ways to
simultaneously increase the yield potential and weed suppression ability of
intercrops? What chemical and physical characteristics of tree leaves and cano-
pies are particularly desirable for suppressing weeds in agroforestry systems?
What species and cultivars are best suited for use in rotation, intercropping,
and agroforestry systems? Modeling will help address these questions (see,for
example, Vandermeer, 1989; Jordan et al ., 1995), but models must be devel-
oped and validated with field data.
A third challenge is technical: realization of the full potential of intercrop-
ping and agroforestry systems will require development of a new generation
of highly adaptable agricultural machinery. Existing farm machinery can be
used to sow, maintain, and harvest many intercrops adapted to temperate
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