Intensification des prairies des marais de l'Ouest. I-Conception d'une expérimentation multilocale

In the low productivity of the pastures in the fens of western France due to environmental constraints, to the techniques in use, or to the place and utilization of grass on the farms ? This is the question a preliminary study and analysis lead to. This paper shows the specifications necessary to the setting-up of a multi-local experimentation plan : choice of locations and of experimental treatments, ways of carrying out the trials. The locations should represent the diversity of situations and utilizations of grass : at the intersection of environmental zones and of farms types. Treatments are constituted by increasing levels of nitrogen, accompanied or not by other techniques of intensification, according to the state of degradation of the pastures. The experimental plots are under the farmers’ usual management. The efficiency of the treatments is measured by comparing their productivity to those obtained without limiting nutritional factors, where growth models will apply. The aim of the study is to set-up technical references, which are lacking in these regions with strong environmental constraints (excess of water).