La diversité de gestion des systèmes herbagers en Amazonie. Cas des élevages bovins brésiliens

Diversity of the grassland system managements in the Amazon region. Case of the cattle farming in Brazil

In the Amazon region of Brazil, there are socio-economic challenges of extreme importance for the development of a sustainable agriculture, particularly for livestock farming. In agronomical terms, they concern the perenniality of the pastures created after the clearing of forest lands, because of the rapid and strong encroachment by weeds. On the farms producing milk and meat, the forage systems are characterized by the exclusive grazing of pastures ; the adequation of the stocking rate to the available forage resources is described as an essential factor for the technical and economic sustainability of these systems. This advice however, technically uniform and essentially stable, goes against the present context of animal farming, with diverse and very rapidly changeing production systems. In order to apprehend the diversity of the forage systems and their determining factors, we have monitored the practices of seven dairy farmers during one year. We have formally defined three criteria of diversity accounting for the variability of the farmers' practices, their objectives, and their determining factors. Linkages among these factors appear, showing the existence of two contrasting policies, viz. producing or maintaining the herd. Over one year, the management policies correspond to other expectations than the adjustment between herbage supply and herd demand, according to the role of stock rearing, the collective work organization and also the production structures. The information we supply will help to characterize and analyze the forage structures, but they will have to be validated on other situations of livestock farming in the Amazon region.