Some universities and colleges allow PCM and PCB both the streams for  Bsc. Agri, only you have to clear entrance exam. Secondly while pursuing degree a non bio student has to take Botany as an extra subject. Some universties allow a non bio student for their two other branches agriculture marketing and Agriculture engineering. for Agriculture Engineering  PCM students are preffered. For B.Sc. forestry PCB stream is must. Private Universities may be exceptions