Hello, there. Glad to know of your interest in two major areas of scientific research and development.

Coming to your query, both agriculture and biotechnology are areas undergoing immense research and development, especially in the last couple of decades. India being an agricultural economy, the agriculture sector has more oppportunies for graduates than that in biotechnology.

Biotechnology is an umbrella term and you will study a gist of many life science subjects and that of allied areas. This makes it imperative for a student to boost it up with a Master's or a Doctorate degree. Moreover, biotechnology is not an industry in itself but more of an amalgamation of varied industries, most prominently pharmaceutical and food (nutraceuticals). Biotechnology, despite the expected boom has a long way to go in India and produce befitting employment opportunities. However, if you ever wish to go abroad, then biotechnology has tremendous potential and is a booming area in US, Australia and Singapore.

B. Sc. Agriculture, on the other hand, is a sector specific course and a different industry altogether. One can secure a decent job right after graduating in agriculture (which is less likely with a B. Tech. Biotechnology).

Thus, if you wish to make a career in India, particularly in public sector, then indeed agriculture would be a better choice. Also you will have biotechnology as a topic during B. Sc. Agriculture which will be in a much more specialised fashion in comparison to what you'd study in B. Sc. or B. Tech. Biotechnology.

Ultimately, what matters more is your interest and ambitions.

Hope this helps.