The development of commercial farming followed the construction of the railroad in the early 20th century, but the main stimulus did not come until World War II (1939–45), when it was necessary to ensure a maximum output of copper and to minimize the shipping space required for food imports. Food production continued to expand as the copper industry helped raise living standards. Additional European immigration in the 1950s, as well as programs to diversify the economy, gave rise to the production for export of tobacco, cotton, and peanuts. However, partly because of the rapidly rising population, agricultural output never reached the point of meeting domestic food requirements. Only 5% of the land area is cultivated at any time, although a much larger area is potentially arable.
The majority of Zambia's population engages in subsistence farming. The principal subsistence crops are corn, sorghum, and cassava, while the main cash crops are tobacco, corn, sugarcane, peanuts, and cotton. In 1992, liberalized marketing began for most crops, but because of the 1991/92 drought, corn marketing remained under government control. A bountiful 1993 harvest made a solid recovery from the drought. In 2001, agriculture accounted for 22% of total GDP.
Production of tobacco, the most important export crop, was estimated at 3,000 tons in 1999. Marketed corn production in 1999 was 856,000 tons (down from 1,096,000 tons in 1991). Cotton production reached 8,000 tons of fiber. Also marketed in 1999 were 1,600,000 tons of sugarcane, 7,000 tons of sunflowers, 57,000 tons of peanuts, and 9,000 tons of wheat.