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

increase the impact of cutting by further reducing the weed biomass production and the
probability of surviving subsequent cuttings.
Besides negative effects of cutting and competition on biomass production, both
processes might also delay or accelerate the phenological development of the weed plants,
which would alter their reproductive output and their chance of surviving subsequent cuttings.
The analysis of plant survivorship under the four treatments (data not shown) indicates that
the plants in higher competition died earlier than the plants in low competition and that the
plants not cut at the early date survived the longest in the case of all species except Adonis
aestivalis, where cut plants survived longer.
CONCLUSION
By comparing cut and uncut plants in more and less competitive environments, we
detected negative effects of both factors on weed biomass production. Our results suggest
that both negative effects will add up when the two factors are combined (case B of Fig. 1 is
thus the most likely situation). This knowledge is important for weed management, as
competition and disturbances are closely related in various situations. These include not only
mown forage crops, but also mown set-aside and field margin strips, annual crops where inrow-mowing
techniques are used for weed control (Donald, 2006) and even grazed pastures.
The concepts and findings presented here might be used to construct a model predicting the
impacts of cutting and competition on weed growth and to optimize the cutting dates for
Integrated Weed Management. In this study, we concentrated on the possible interactions
between disturbances and competition; future studies should also investigate possible
interactions between competition, disturbance and other stresses perceived by the weed
plants.
ACKNOWLEDGEMENTS
We would like to thank Delphine Ramillon and Sébastien Brenot for assisting with the
greenhouse experiment and Richard Gunton for correcting the English text. This work was
funded by the ECOGER program (INRA) and the Etablissement National d’Enseignement
Supérieur Agronomique de Dijon (ENESAD) and supported by a PhD scholarship from the
French research ministry to H.M.
REFERENCES
(at the end of the thesis).
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