Is paying a sum of money to the landowner in exchange for utilizing their land for cultivation during the mortgage period, in order to avoid Riba (usury), permissible in Islam?

If the religion (i.e., the transaction) was a loan, then it is not permissible for you to benefit from the mortgaged farm, because your loan would have brought a benefit, and every loan that brings a benefit is usury (riba). The farm is still the property of the mortgagor; he is entitled to its profits and bears its losses, according to the Prophet, peace and blessings be upon him: "A mortgage is not forfeited from its owner; he is entitled to its profits and bears its losses." Therefore, it is not permissible for you to benefit from this farm, nor should you give its owner something and take the rest due to the ambiguity (jahala) and excessive risk (gharar) involved. What is incumbent upon you now is to return the farm to its owner, ask for his forgiveness, and seek Allah's forgiveness.