Organic farming guidelines ban the use of artificial fertilisers such as manufactured mineral phosphorus (P) fertilisers and emphasize the need for recycling nutrient resources. In consequence, organic production may be considered as a prototype of sustainable agriculture that maximises P recycling and saves fossil P resources. This assumption has been tested through the detailed analysis of P inflows for 63 organic farms distributed into three French agricultural districts differentiated by their specialisation (mixed vs specialised in crop productions or in animal productions). Results showed that P recycling was higher in the mixed district due to exchanges of organic materials between grain growers and livestock farms. However, overall, 73% of the P entering organic farms came from conventional farming through import of conventional manure or straw. Combining these results with a model accounting for the origin of soil P accumulated before conversion to organic farming, it was shown that approximately 71% of the P contained in organic products derived indirectly from artificial P fertilisers. These results raised the question of the indirect reliance of organic farming on mineral P fertilisers. They are discussed in terms of P management in organic production and of global fossil P resource use.