The system of agriculture where a single crop is grown on a large area is called "Plantation Agriculture." In plantation agriculture, large-scale cultivation of a single crop species occurs primarily for commercial purposes, often involving crops like tea, coffee, cotton, cocoa, sugarcane, and rubber. This method requires significant labor and capital investment and is practiced in various regions such as Assam, Tamil Nadu, Karnataka, Kerala, and West Bengal. A related term is "Monoculture farming," which also describes growing a single crop species over large areas, often used in mechanized agriculture for efficiency but with certain environmental concerns. Thus, the best description for a system of agriculture with a single crop grown on a large area is Plantation Agriculture, closely linked to the concept of monoculture farming.