One quarter of Tunisia's labor force is employed in agriculture. Grapes, oranges, and figs are grown on Cape Bon and near Tunis and Bizerte. Although the size of the harvest varies, Tunisia usually is the world's fourth largest producer of olive oil. Dates are grown at Gafsa, Nefta, Tozeur, and other oases in southern Tunisia. Most crops are grown by dry-farming methods.
Agricultural production varies widely, primarily because of erratic rainfall.
Tunisia has had to import cereals, as demand exceeded domestic production. Tunisia is rich in petroleum and calcium phosphates. Petroleum, which is the principal source of export earnings, was first discovered in 1964 at El Borma, near the Algerian border in southern Tunisia. Seven fields in Tunisia and three in the Gulf of Gab s produce petroleum. The offshore fields account for half the total production.