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To cite this version:François Coléno, Frédérique Angevin, Baptiste Lécroart. A model to evaluate the consequences of GM and non-GM segregation scenarios on GM crop placement in the landscape and crosspollination risk management.

Managers of extensive livestock systems generally have 2 goals for permanent grassland management: to obtain sufficient dry matter to feed animals and to avoid the establishment and dominance of unpalatable species. Hay production in French Pyrenean meadows is dependant on the need to balance grazing and cutting dates to produce maximum biomass for hay stock and to prevent seed recruitment of Chaerophyllum aureum L., one of the major invasive unpalatable species. Experiments and observations on a set of meadows within farms show that optimal dates calculated from degree-days for cutting or spring grazing of C. aureum fitted to seed production and apex development respectively, decreases hay yield. This decrease is related to the earliness of the cut in regard to sward growth or to the biomass loss by senescence due to the vegetative regrowth of the sward after spring grazing. Compromises and choices have to be made for each meadow by the farmer according to its potential production, the risk of invasion by C. aureum, and its role in the forage system.

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