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

anches ramifying near to the soil surface are likely to keep part of their buds. The intra-
specific variation of plant height and morphology may be simulated in the same way as for
‘A’.
D, the ‘general growth conditions’ determined by the availability of water, nutrients and light
as affected by the soil, the climate and the crop management practices are already partly taken
into account by the current versions of the FLORSYS and ALOMYSYS models. However,
the general growth conditions may also interact with the impacts of cuttings and regrowth
abilities of weed plants. Modifications in the growth resources and conditions (including weed
control) may thus have stronger (or weaker) impacts on cut plants in PFCs compared to
(uncut) weeds in annual crops. Some, but not all, of these interactions are already taken into
account by simulating the impacts of the general growth conditions on ‘A’, ‘B’, and ‘C’
(detailed above). Experimental results reported in Article 5 suggest that the interactions
between the impacts of cutting and competition are mainly additive (Fig. 3 of Article 5). The
mechanistic representation of the processes should thus account for these additive effects of
cutting and growth conditions. However, possible interactions with other factors are not yet
accounted for by FLORSYS. Cut weed plants might e.g. be more vulnerable to fungal or
bacterial pathogens than uncut plants which may also offer possibilities for combined
mechanical and biological weed control (Kluth et al., 2003).
At this stage, results from the greenhouse experiments might support some suggestions for
basic formalisms to simulate weed and crop regrowth after cutting that could be introduced in
the FLORSYS model. This could be based on the conceptual formula mentioned above: R =
(A + B) * C * D.
Given i) a sufficient number of buds/meristems remaining after a cutting event (C > 0) and ii)
favourable general growth conditions (D), the ‘daily aboveground biomass increase’ (ΔBMj)
of a cut plant depends on both the photosynthetic activity of the residual plant surface during
day j (ΔBMphsynth j,) and on the remobilization of carbohydrates during day j (ΔBMremob j)
:
ΔBMj
= ΔBMphsynth j + ΔBMremob j .
Directly after the cutting event, the daily biomass production (ΔBMj)
would go down due to
the loss of green surface ( Fig. 24).
During the following days, the lack of energy and
carbohydrates may partly be compensated by remobilisation re-increasing ΔBMj again
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