Andhra Pradesh's economy is mainly based on agriculture and livestock. Four important rivers of India, the Godavari, Krishna, Penna, and Tungabhadra flow through the state and provide irrigation. 60 percent of the population is engaged in agriculture and related activities. Rice is the major food crop and staple food of the state. It is an exporter of many agricultural products and is also known as "Rice Bowl of India". The state has three Agricultural Economic Zones in Chittoor district for mango pulp and vegetables, Krishna district for mangoes, Guntur district for chilies.