Microbiology

Sonali, I would suggest for Microbiology. It is a growing field and already opening for it are on the increase. Research based industry which is into developing products / processes through Biotechnology would be the ideal for you to make a career.

Microbiology is the scientific study of these microorganisms. Microorganisms are those organisms that are too small to see with the naked eye and include things like bacteria, fungi, and viruses.

B.Sc Micro and Bio chemistry courses are common and there are many colleges that offer these courses. But agricultural engineering is a rare branch , only few institutions conduct this course. So its more demanding course than Bio chemistry and Microbiology
Agricultural engineers have opportunities in agricultural research centers, universities , large scale nurseries, plantations etc.

Jadavpur university, Calcutta university gives B.Sc. Microbiology and Raja Bazar Science College kolkata gives you opportunity to pursue 80% in B.Sc. Microbiology

choose that one in which you have interest. coz salary doesn't matter if you don't have joy in the job.

You should refer the prospectus of colleges. Every college has different fee criteria.