The Kura River valley is the region's chief agricultural zone. Wheat, barley, corn, fruits and vegetables, wine grapes, and potatoes are the leading food crops, and cotton, silk, and tobacco the foremost industrial crops. The subtropical Lankaran Lowland produces tea and rice. The Absheron peninsula is one of the richest oil regions of the world. Although production of Caspian Sea oil and gas had declined for several years, it began growing again in the late 1990s under production-sharing agreements with multinational corporations. The republic's other mineral resources include natural gas, iron ore, copper, lead, zinc, limestone, pyrites, cobalt, and alumina. Widespread salt springs have enabled health resorts to flourish. Among the chief manufactures are petroleum products, oilfield equipment, steel, chemicals and petrochemicals, and textiles. The old craft of carpet weaving is still practiced. Azerbaijan's main trading partners are Italy, Russia, and Turkey.