Hi dear...There are number of good Colleges In Tamil Nadu with excellent placement and infrastructure.

Vanavar Institute Of Agriculture

Annamalia University ( B.Sc + B.Tec is also available here), Chidambaram

Krishna College of Agriculture And Technology, Doddappanaickanur 

Agriculture College and Research Institute , Coimbatore

Bharat University - Bharat Institute of Higher Education and Research

Thiruvalluvar University

RVS Agriculture College , Thanjavur

PGP College Of Agriculture Science, Namakkal

Horticulture College And Research Institute

College Of Agriculture Technology- Tamil Nadu Agriculture University- Theni

Imaym Institute of Agriculture And Technology, Trichy

 The Gandhigram Rular Institute Deemed University, Dindigul.

For admission in Agriculture cource , Aspirant have to appear AIEEA exam, conducted by ICAR for admission in U.G and P.G  Agriculture cources. Agriculture specialisation can be done in Forestry, Horticulture, Plant Pathology, Floriculture, Plant Pathology and many others

All the Best

Hey,
Here is the list of some of the colleges that offer Bachelor of Science(B.Sc) in Agriculture in Tamil Nadu:
1.Tamilnadu Agricultural University
2.Veterinary College and Research Institute
3.Anbil Dharmalingam Agricultural College and Research Institute
4.Vanavarayar Institute of Technology
5.Tamil Nadu Veterinary and Animal Sciences University
6.Horticulture College and Research Institute
7.Agricultural College and Research Institute,Madurai
8.Agricultural College and Research Institute,Thoothkudi
9.Annamalai University
10.Vellore Institute of Technology
11.SRM University Kattankulathur
12.Bharathidasan University
13.Madurai Kamraj University
Hope this helps.
Good luck.