Les sécheresses passées et à venir : quels impacts et quelles adaptations pour les systèmes fourragers ?

Past and future periods of drought : what are their effects on the forage systems and the possible adaptations ?

The rearing of herbivorous stock is very sensitive to drought as the largest water requirements of pastures and of maize take place in the period May-July, when rainfall is very erratic. A quick reminder of the past severe droughts will bring to light the various ways in which the forage systems reacted and adapted to drought. The analysis of the 1976 and 2003 droughts shows that the herbage systems in the strict sense and the 'organic' systems were those that suffered most, in spite of the rather remarkable aptitude of grasslands for recovery. The farmer may anticipate a period of drought by including some strategic adaptations in his system (grazing management, constitution and postponement of forage stores, recourse to annual forages, dual-purpose crops such as maize…). If the drought is too severe, other adaptations, of tactical nature, have to be considered (purchase of forage, of straw or of concentrate, change in the livestock management) in order to save the animals. In view of the growing risk of severe and frequent droughts, the preference is to be given to a strategy that gives the best utilization of the rainfall and of the soil water reserves during winter and spring (winter crops or crops with deep roots, winter grazing…).