Is it permissible for a contractor to pay a sum of money to a farmer to carry out the free "Agricultural Support" project in Algeria, knowing that the execution of the project requires a contractor?

The picture the questioner asked about is not clear to us. However, if the contractor will give the landowner money as a donation or a goodly loan to establish the project, there is no harm. But if it is on condition of returning more than that, then it is forbidden usury.

If he will give him money and buy agricultural supplies, and the produce will be shared between them, then this is a void sharecropping agreement according to the majority of scholars, because it is renting the land for a portion of what it produces.

The legitimate solution is for the contractor to take the land on lease for a specific amount and seek the help of its owner for a wage, or for the landowner to perform the work and provide the seeds.