Hey Mohit,
There are so many differences in both the degrees about subjects, base of course, etc.
BSc in Horticulture is a 3-year undergraduate degree course, firstly get to know about basic meaning of Horticulture that is ' cultivation of plants' and Horticulture is small scaled as compared to agriculture, this course includes scientific study of cultivation, plant diseases, genetics of plants etc. and aims at increasing  productivity and yield of plants by using the applications of Biochemistry, Biology, and Genetic Engineering etc.


BSc Agriculture is a 4-year undergraduate degree course in which you study about using modern scientific equipment and techniques for prospering agricultural sciences and includes studying aspects of water resource management, land surveying, soil sciences, and poultry management, cattle ranching, etc for improving agricultural productivity. The main subjects included in the course are Agriculture (Agronomy), Veterinary Science, Forestry, Fisheries, Horticulture, Home Science.
Also we can say that Horticulture is one of the branch of Agriculture field.

Good Luck!