If you are passionate about doing Bsc course in agriculture then you can apply for the exam again.  Prepare as if you have no other option. Also incase you lose hope, self motivation is the only key. You can also apply for general bsc courses side by side as admission is based on merit mostly unlike Bsc Agriculture course.

To know more about the scopes and details about the same check in the link below:

BSc Agriculture- All about!!

Good Luck!!