What is the message behind the two contrasting descriptive paragraphs of the land around Ixopo?

The land of the whites is rich and fertile, while the land of the blacks is barren and infertile. Paton is setting the basic premise of the haves and the have nots. The blacks, although the original inhabitants, have been pushed aside to land that cannot sustain them, partially due to a lack of knowledge about modern farming techniques. This leads to the young leaving the countryside for the city and the "breaking" of the tribe.