Abstract:

Searching for multiple sustainable levers to control weeds in arable fields and reduce the use of herbicides, cover crops (i.e. the plants sown after the harvest of a previous cash crop and terminated before the sowing of a following one) are a lever to explore. Particularly through the competition they generate, cover crops can biologically control weeds during the cover- and subsequent cropping periods, but their effects depend on numerous factors that may interact (e.g.  pedoclimate, flora, farming practices). The objectives of this thesis were to identify the drivers of cover crop weed control during the cover- and subsequent cropping periods at different temporal scales, and to quantify their effects. A first series of field experiments  identified cover crop composition and termination method as major drivers of weed control during the cover- and subsequent cropping periods. Although experimentations did not include any practices known to override cover crop effects on weeds in the cover- and subsequent cropping periods (e.g. tillage, weeding, fertilisation), the effects observed beyond the cover cropping period were very weak. Complementary field and greenhouse experiments showed that cover crop nitrogen supply can mediate the subsequent crop-weed competiton intensity. Looking foward, further research are needed in various production contexts by combining experimental and simulation studies, in order to increase the genericity of the results otained in this thesis. 

Thèse soutenue le 9 novembre 2023

Le jury est composé comme suit :

Mme, Valantin-Morison, Muriel           Directrice de recherche, INRAE, Paris-Saclay         Rapportrice
M., Alletto, Lionel                                    Directeur de recherche, INRAE, Toulouse              Rapporteur
Mme, Wirth, Judith                                Directrice de recherche, Agroscope, Changins      Examinatrice
M., de Tourdonnet, Stéphane               Professeur, l’Institut Agro Montpellier                   Examinateur
M., Redecker, Dirk                                   Professeur, Université de Bourgogne, Dijon          Examinateur