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

crops will thus probably show rather increasing population densities during the phase of
annual crops, especially at the end of the phase of annual crops, when the OSFs are introduced
(illustrated in Fig. 7). In contrast, the perennial crops may provide rather unfavourable
conditions to several arable weed species adapted to annual crops as suggested by several
previous studies reviewed in section A.IV.1 above). Therefore, the population densities of
such arable weed species may decline during the perennial crops. At the same time, other
plant species may profit from the specific conditions in perennial crops including the absence
of soil disturbance during several years (see below). Perennial crops may thus cause weed
community shifts. Following this hypothesis, the alteration between phases of annual and
perennial crops would result in dynamic changes of the weed communities (illustrated in Fig.
7).
Weed abundance
a) annual crops c) perennial crop
a) annual crops
b) OSFs
Time (years)
Fig. 7: Illustration of the modified cropping system (upper part) and hypothetical population dynamics of
different weed species (lower part).
Upper part: Successions of conventionally managed annual crops (simple crop rotations or monocultures) are
replaced by a temporal alteration between periods of (a) annual crops (diverse crop species with integrated weed
management and less herbicides) (white boxes), (b) untilled overwinter stubble fields (OSFs) or other agrienvironment
schemes concerning the whole field area (striped boxes) and (c) perennial crops (PFCs) lasting
several years on the field (grey boxes).
Lower part: Hypothetical population dynamics of (i) weed species adapted to annual crops but not to forage crops
(black line with dots) and (ii) of species favoured in perennial but not in annual crops (broken line).
This might result in lower pressures of the most noxious arable weeds in the annual crops
following the perennial crops. If this is the case, the diversification of crop rotations with
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