It has been proven that with cheap (basically slave) labor, one takes away the motivation for ingenuity. Technological advances in strawberry picking, say, will only come around when the pickers must receive a decent wage and benefits. Suddenly someone will invent the mechanical strawberry picker.
And that is exactly one of the big problems with Mexico itself. They didn't need to import tractors --- they had plenty of peasants with machetes and hoes and shovels. They had cheap labor galour --- they felt no need to invent or even to bring in the inventions of countries like the USA.
Now --- in the country where corn and beans were developed, the farmer cannot come close to competing with the American farmer because they still lack technology and the cheap labor does them no good at all --- now Mexico imports it's corn and beans and the farms have gone bankrupt.