South Sudan has fertile and well-watered soils, and the economy is overwhelmingly agricultural. Much farming is subsistence-based, with shifting cultivation and herding. The main subsistence crops include sorghum, maize, and other grains, tropical fruits, and sweet potatoes and cassava; the chief cash crop is cotton. Cattle, goats, and other livestock are raised, and forest products such as gum arabic and tropical hardwoods also are produced. Fish caught in the country's rivers and swamps are an important dietary staple. Industry is little developed. Most manufacturing facilities were destroyed during the civil war, but there is some food processing. Oil, discovered in 1978, is present in significant deposits in the north, and the fields have been extensively developed. Nearly all government revenues come from oil exports, which are transported via pipeline to Port Sudan, on the Red Sea in Sudan. Uranium, gold, and other mineral resources have not been exploited, and the country's hydroelectric resources are undeveloped. There are few paved roads. Sudan, Uganda, and Kenya are the country's leading trade partners.