, about 30% of Nigerians are employed in agriculture. Agriculture used to be the principal foreign exchange earner of Nigeria. Major crops include beans, sesame, cashew nuts, cassava, cocoa beans, groundnuts, gum arabic, kolanut, maize (corn), melon, millet, palm kernels, palm oil, plantains, rice, rubber, sorghum, soybeans and yams. Cocoa is the leading non-oil foreign exchange earner. Rubber is the second-largest non-oil foreign exchange earner.