Farming as a business in Africa depends upon the political climate within the country in question as well as the climatological and biological environments. In most of equatorial Africa farming as a business is not likely. Too much jungle and animal life to be cleared for it to be practical. In the Sahara region the desert poses the main problem. Without irrigation farming is not likely to succeed and irrigation requires lots of available fresh water. A very scarce commodity except in Egypt and parts of Ethiopia.
The political climate needs to be one that recognizes the ownership of the land and proper property rights. Much of southern Africa is not in a state of turmoil concerning this. Until this stabilizes not much can be done there either.
The ability of giant agri-businesses like flourish in the US and parts of Canada occurring in Africa appear to be, at least on the surface slim. Also, not sure they need them there. It took a century or more for them to evolve in the U.S, and Africa is just truly starting on that journey.