The difference in kind between the pre-colonial and the postcolonial relations of production can he noticed through the gradual dissolution of relations based on a personal tieless gift-giving based on the market economy. The liberation of the labor forces this engendered and of channeled into a new system of constraint, led to the beginning of a private appropriation of land.

Yield trials with farmers and acceptance surveys were conducted in Colombia in 1969-1970 to assess the potential use of opaque-2 maize in the tropical regons of the country. Yields were variable, particularly from one farm to another. In spite of this variability which may have confused the results, and analysis of variance was applied, using farms as replications.