Translate the following English sentence to French:
"But every farmer who has made an investment in this area signed a contract at the outset before he made that investment, so that he knew for exactly how many years he would be receiving investment aid."
Mais chaque agriculteur qui a effectué un investissement a, dès le départ, avant d'effectuer cet investissement, signé un contrat lui précisant exactement le nombre d'années pendant lesquelles il bénéficierait d'une aide d'investissement.