"The economy is heavily based on agriculture, which accounts for more than 25 percent of gross domestic product, provides 85 percent of exports, and employs 80 percent of the workforce;[7] 12.25 percent of the land is arable, but only 1.79 percent of the land is planted with permanent crops.[7] Maize dominates much of the country, with cassava, rice, millet, sorghum and coffee also grown. According to the 2002 National Irrigation Master Plan, 29.4 million hectares in Tanzania are suitable for irrigation farming; however, only 310,745 hectares in June 2011 were actually being irrigated.[56]"

From our friend wikipedia on Tanzania