In almost all Goverment colleges, admission in Bsc Agriculture happens direct through the marks of 12th of any student.

But There is a all India entrance exam for Bsc Agriculture Conducted by ICAR. If you crack this exam(Icar ug), you can get admission in any government college throughout India according to your rank. In every Goverment college there is 15% seat reserved for the student through ICAR exam. To appear in this exam every student should need 50% in their 12th.

Apart from that there are many Private college, that offers the course Bsc Agriculture. In Private colleges there are no barrier of marks, money talks there!