Recoupling of crop and livestock production: a prerequisite to close biogeochemical cycles?

Specialisation of farms and spatial segregation between crop and livestock production systems havehampered the proper recycling of nutrients. As a result, N and P budgets are often in excess in intensivelivestock regions, whereas intensive arable regions rely on mineral fertilisers. Despite progress inadjusting mineral supply to animal needs in feed rations, nutrient use efficiency by animals remains low,between 10 and 60% depending on the animal species and livestock system. Conversely, the efficiencyof use of N and P supplied by animal manure by plants is close to that observed for soluble mineralfertilizers since the methods and schedules of intake allow a supply of nutrients synchronous with plantneeds. Therefore, an overall high efficiency of the system requires a recoupling of crop and livestockproduction systems. Innovative technical or organisational levers, at several organisation levels, mayhelp reaching this recoupling.