Diversifying crop rotations with temporary grasslands - Université de ...

competitive yield loss (Cousens, 1985; Caussanel, 1989) and (ii) about the values of the
different species for biodiversity and ecosystem functioning, which is a rather recent research
area (Gerowitt et al., 2003; Marshall et al., 2003; Holland et al., 2006; Storkey, 2006).
However, both the harmfulness and the biodiversity values of weed species might differ
between crops and regions and detailed knowledge is often lacking. The classification of weed
species into more ‘beneficial’ and ‘harmful’ groups by Storkey (2006) are based on British
data, classifications in other regions might differ. Moreover, indicators for biodiversity such as
the number of associated insect species and the value of weed species for granivorous birds
might underestimate the value of e.g., rare weed species supporting endemic animals with
very specific diets or habitat requirements or still unknown ecosystem functions and potential
human uses. Second, strategies based on the distinct management of the most ‘harmful’ and
the most ‘valuable’ weed species would require techniques that are able to selectively control
the harmful species. Last but not least, it would need training of farmers and consultants to
make them agree with the idea of ‘protecting’ a list of weed species in their own fields,
whereas their current practices mostly aim at suppressing all wild species.
A.III.5 Favouring weed seed predation
One rather new approach to alleviate the ‘weeds trade-off’ may be the promotion of weed seed
predation, e.g. the consumption of weed seeds by animals, which might alleviate the three
problems of agriculture linked to weeds and thus create a ‘win-win-win situation’ (Table 2):
Table 2: Conceptual overview showing the central role of weeds in three big challenges of modern agriculture
and the potential contribution of weed seed predation to solve these three ‘weed problems’.
A) Challenges
B) Roles and
C) Potentials of
of modern agriculture
conflicts of weeds
weed seed predation
1) Loss of biodiversity in
farmlands must be stopped
(functions, heritage,…)
2) Consumption of inputs must be
reduced
(pollution, natural resources, capital)
3) Agricultural production must be
increased or stabilized
(increasing demand)
1) weed diversity loss,
animal diversity loss,…
2) herbicides massively
used for weed control
3) weed control needed to
prohibit crop yield loss
(competition, contamination)
14
Energy for food chains
(biodiversity)
Reduction of weed seed
densities
(preventive weed control,
economy of herbicides)