Diversifying crop rotations with temporary grasslands - Université de ...
Diversifying crop rotations with temporary grasslands - Université de ...
Diversifying crop rotations with temporary grasslands - Université de ...
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
anches ramifying near to the soil surface are likely to keep part of their buds. The intra-<br />
specific variation of plant height and morphology may be simulated in the same way as for<br />
‘A’.<br />
D, the ‘general growth conditions’ <strong>de</strong>termined by the availability of water, nutrients and light<br />
as affected by the soil, the climate and the <strong>crop</strong> management practices are already partly taken<br />
into account by the current versions of the FLORSYS and ALOMYSYS mo<strong>de</strong>ls. However,<br />
the general growth conditions may also interact <strong>with</strong> the impacts of cuttings and regrowth<br />
abilities of weed plants. Modifications in the growth resources and conditions (including weed<br />
control) may thus have stronger (or weaker) impacts on cut plants in PFCs compared to<br />
(uncut) weeds in annual <strong>crop</strong>s. Some, but not all, of these interactions are already taken into<br />
account by simulating the impacts of the general growth conditions on ‘A’, ‘B’, and ‘C’<br />
(<strong>de</strong>tailed above). Experimental results reported in Article 5 suggest that the interactions<br />
between the impacts of cutting and competition are mainly additive (Fig. 3 of Article 5). The<br />
mechanistic representation of the processes should thus account for these additive effects of<br />
cutting and growth conditions. However, possible interactions <strong>with</strong> other factors are not yet<br />
accounted for by FLORSYS. Cut weed plants might e.g. be more vulnerable to fungal or<br />
bacterial pathogens than uncut plants which may also offer possibilities for combined<br />
mechanical and biological weed control (Kluth et al., 2003).<br />
At this stage, results from the greenhouse experiments might support some suggestions for<br />
basic formalisms to simulate weed and <strong>crop</strong> regrowth after cutting that could be introduced in<br />
the FLORSYS mo<strong>de</strong>l. This could be based on the conceptual formula mentioned above: R =<br />
(A + B) * C * D.<br />
Given i) a sufficient number of buds/meristems remaining after a cutting event (C > 0) and ii)<br />
favourable general growth conditions (D), the ‘daily aboveground biomass increase’ (ΔBMj)<br />
of a cut plant <strong>de</strong>pends on both the photosynthetic activity of the residual plant surface during<br />
day j (ΔBMphsynth j,) and on the remobilization of carbohydrates during day j (ΔBMremob j)<br />
:<br />
ΔBMj<br />
= ΔBMphsynth j + ΔBMremob j .<br />
Directly after the cutting event, the daily biomass production (ΔBMj)<br />
would go down due to<br />
the loss of green surface ( Fig. 24).<br />
During the following days, the lack of energy and<br />
carbohydrates may partly be compensated by remobilisation re-increasing ΔBMj again<br />
173