If drought or hail destroyed the crops, oxen could be put into the fields to eat what was left. Then came hybrid maize varieties and extra fertiliser had to be added to prevent any weeds growing. Herbicides came next, and hand hoeing, mules and oxen were done away with. Tractors now did most of the work.
Woe betide if there was a drought or hail. The oxen did not get fat on eating hybrid stalks. Due to these factors, the yield did not materialise and crops were a total failure and financial loss. When ‘super hybrids’ came along, followed by GMOs, any hail, drought or crop failure meant bankruptcy.
After the Second World War, there were displaced people all over Europe, who subsisted on meagre amounts of potatoes and wheat (stolen) from the fields. Those who immigrated to the USA were horrified that locals had to buy so much food in supermarkets and still managed to become overweight. They realised the nutritional quality of this produce was not the same as in countries where modern agricultural methods were not used.
I would therefore not recommend going for large lands and fleets of modern combine harvesters in southern Africa. The quality of the produce grown in this way does not contribute to good health, despite large populations being fed for little cost.