When you get to the end, remember that's how many to most black people lived until very recently until they were expelled from the land with nothing, due to the rise of more efficient farming techniques. The very few who owned their own land were more slowly pushed out when they were denied farm loans. Black people owned about 15 million acres of land in 1910, now they own about 1 million.
The idea that "efficiency" alone caused it glosses over how policy and power structures actively shaped who got to benefit from modern agriculture and who got left out (or pushed out).