Because of the lack of natural resources and the primitive industrial base in Cambodia, agriculture is the key sector in the economy. Arable land amounted to 3,807,000 hectares (9,007,000 acres) in 1998, or 22% of the total land area. In 2001, agriculture accounted for 50% of GDP and engaged 80% of the economically active population.
Rice provides the staple diet and prior to 1970 was Cambodia's major export, along with rubber. Production peaked at 3,200,000 tons in 1968; it began falling because of the expansion of the war and by 1974 had declined to 635,000 tons, but had risen back to 2,155,000 tons in 1990. Production in 1999 totaled 3,800,000 tons from 1,961,000 ha (4,846,000 acres).
Upon coming to power in April 1975, the Pol Pot regime embarked on a major rice production program, but the highest output achieved was only 1,800,000 tons in 1976 and in 1977; civil war, holocaust, and the Vietnamese invasion lowered the rice harvest in 1979 to one million tons. During the 1980s, rice production gradually increased, from about 1,564,000 tons in 1980–81 to an estimated 1,680,000 tons in 1985/86. During the mid–1980s the Khmer Rouge government attempted to stimulate production by delaying its plans for collectivization of the countryside. In 1989, the new government returned agricultural land to the tiller, which significantly boosted food production; average annual production in 1989–91 was 2,524,000 tons.
Rubber has traditionally been the second most important agricultural crop. However, rubber plantings, which covered 48,000 hectares (119,000 acres) in 1969, were almost completely destroyed by the end of 1971. Production, up to 51,100 tons in 1969, declined to virtually nil in 1971, recovering to about 16,000 tons in 1974. The Pol Pot and Khmer Rouge governments continued efforts to revive the rubber industry, the latter with aid from the former USSR and GDR. Recovery has been uneven and slow, however, and reached 40,000 tons in 1999. Other crops, with 1999 production levels, are: coconuts (56,000 tons), corn (50,000 tons), soybeans (28,000 tons), sweet potatoes (25,000 tons), dry beans (11,000 tons), cassava (68,000 tons), tobacco (10,000 tons), and peanuts (7,000 tons).