Hey Aspirant,
After completing Agriculture diploma you will have a chance in pursuing your career in agricultural fields like in agricultural nurseries , farm production activities,  and work in industries related to it or you can pusue BSc agriculture after Agriculture diploma and further after BSc agricultural you can go for pursuing MSc in agriculture and then you will have a career option as lecturer or professor in a good institution which is a very good career opportunity and you can also work in government organizations like farmer welfare, food management, horticulture and many other after agricultural diploma.