Hi Aspirant,
Congratulations for a quite good score in BCECE.Generally many people don't opt for agriculture and the competition is relatively low in the field of agriculture be it studying bsc or btech.
So you can get chance in a good college in Bihar with the moderate rank in BCECE.Generally,rank above 670 will fetch you a good college in agriculture.You can opt for BIHAR AGRICULTURAL UNIVERSITY ,Jawaharlal Nehru college or Dr Rajendra Prasad College.
All the best for your future.