From the report “Is muscle or machine the future of agriculture in Africa?“, from

Most of sub-Saharan Africa’s economies are dominated by the agriculture sector. But despite being a crucial sector in many economies, agricultural productivity on the continent is very low. Yields of maize and other staple cereals have typically about 1/3 of the average achieved in Asia and Latin America.
The greatest source of power for land preparation in sub-Saharan Africa remains human muscle power. On average, less than 20% of mechanisation services are provided by engine power in sub-Saharan Africa. Higher levels of mechanisation are linked to economic growth, improved farm productivity, higher incomes and greater food security. But if mechanisation is not done right, it can potentially burden small farmers with machines they can’t afford or maintain and tools that eliminate jobs and disempower wage earners.
Sub-Saharan Africa was therefore largely bypassed by the Green Revolution that helped transform agriculture and reduce poverty in Asia and Latin America. Nonetheless, it is clear that sub-Saharan Africa can no longer rely on human muscle power to feed its growing population.