Influence of crop-livestock integration on direct and indirect contributions of beef systems to food security

CONTEXT: Beef production systems have been criticized for their low conversion efficiency of the human-edible feed and the agricultural land they use, impacting their ability to contribute directly to food security. However, beef cattle can also contribute indirectly to food security by transferring nutrients from permanent grasslands to marketed food crops through manure. OBJECTIVE: The objective was to analyze the relations between direct and indirect contributions to food security and assess these two aspects for Walloon beef farms. We hypothesized that crop-livestock integration was positively associated with both contributions. METHODS: We calculated indicators of direct and indirect contributions to food security and crop-livestock integration on farm accounting data of 73 Walloon beef farms. The direct contribution was represented with the net productivity, while the indirect contribution to food security was represented with two indicators. The first was the share of exported manure from the livestock subsystem to marketed crops. However, as this manure could be produced out of imported nitrogen, we calculated a nitrogen balance where natural N deposition and fixations are not taken into account, which enables a negative N surplus representing a "net " nitrogen export from livestock towards marketed crops. We calculated correlation coefficients between all indicators and performed a clustering on the indicators of food security contribution, at farm and livestock subsystem levels. RESULTS AND CONCLUSIONS: While the livestock subsystem of two farm types out of five did not contribute positively to food security, the presence of marketed crops resulted in a positive net productivity at farm level. In term of indirect contribution to food security, the share of marketed crops was linked with a higher share of exported manure. However, the higher the share of exported manure, the higher the N surplus of the livestock subsystem implying that the manure is produced out of imported nitrogen sources and not from the valorization of permanent grasslands' fertility. The indicators of crop-livestock integration were mainly associated with a low N surplus but the intra-consumption of crops was negatively associated with net productivity. SIGNIFICANCE: Although they can provide manure to marketed crops, current beef cattle use imported N sources to do so and do not always contribute directly to food security. Those performances could be enhanced by combining a grass-based beef cattle subsystem that is self-sufficient in N and intra-consumes small amounts of crops with a marketed crops subsystem that uses manure exported from the livestock subsystem.