Hi, Some of the good colleges to pursue Btech in agriculture are:

1. TNAU, COIMBATORE 

2. VANAVARAYAR INSTITUTE OF AGRICULTURE, COIMBATORE

3. AGRICULTURAL COLLEGE AND RESEARCH INSTITUTE, MADURAI 

4. AGRICULTURAL COLLEGE AND RESEARCH INSTITUTE, THOOTHUKUDI

Also the process of selection in different in each universities/colleges.

You can specify me the college name you want to know the eligibility criteria or joining criteria for?

Hope this helps.