In case of Tamil Nadu Agricultural University (TNAU), the eligibility criteria is 10+2 with 55% aggregate of all 4 main subjects. So according to this criteria, you are eligible for BSc Agriculture. There are other private colleges as well with their own set of criterias. It varies for every college. I'm sharing a link that can help you better with regards to your question.

http://icarcolleges.in/newsite/tamil-nadu/

Hope this helped.