All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
If the person from whom you borrowed the money conditioned on you to give him half of the crop in addition to the amount of debt, then it is not permissible for you to give him that because this surplus (half of the crop) is Riba (interest and/or usury), and the Prophet said: “Allaah has cursed the one who consumes Riba (i.e. usury or interest), the one who gives it to others, the one who records it and the one who witnesses it (its transaction).” He said: “All of them are equal in sin.” [Muslim]
The scholars stated that the mortgagee (the lender) benefiting from the mortgage –which is the land here –is considered as Riba, therefore, it is not permissible for him to take anything from the crop, and it is not permissible for you to give him anything more than the amount of debt if he conditions it or asks for it.
For more benefit, please refer to Fatwa 90508
Allaah Knows best.