HI, You will have to clear the entrances to apply for this course.
get your basics clear, with proper current syllabus and marking.
Apart from focusing on previous year sample papers you will have to focus mainly on sectional and full length mocks.
Also make sure you analyse you performance in mocks so that you get the right direction.
What exams you are focusing upon?

You can check the list of some of the good agricultural universities here:
Agriculture Universities