Rural to urban migration: Unskilled (subsistence) farmers migrate to cities and start working in factories. Over night, this increases their productivity many times over.
Perhaps tangential, but unless the urban workers are fed by imports, in order to allow rural to urban migration, the country needs agricultural improvements so that people can feed a lot more than themselves. So I think the green revolution technologies of fertilizer, pesticides, and improved crop varieties (mentioned by the OP) are quite important beyond the direct food supply improvement, and the penetration of these is much lower in Africa.
Perhaps tangential, but unless the urban workers are fed by imports, in order to allow rural to urban migration, the country needs agricultural improvements so that people can feed a lot more than themselves. So I think the green revolution technologies of fertilizer, pesticides, and improved crop varieties (mentioned by the OP) are quite important beyond the direct food supply improvement, and the penetration of these is much lower in Africa.