The isolation of Cuba caused a severe shortage of chemicals and petroleum products and threatened the population with starvation. The farmers used their available resources to create fertilizers from vermiculture using manures and sugar cane residues. This knowledge has been spread across Central and South America by educators from Cuba. During these difficult times the suffering was most acute in downtown Havana. The USSR helped to create hydroponic systems in the city, but the collapse of the Soviet Union caused an end to the availability of chemical nutrients. The Cubans shifted from inorganic hydroponics to organic hydroponic gardening. Here is one of many sources that you may find enlightening:
(ORGANOPONICO! AN AGRICULTURAL REVOLUTION)(Sorry about not being a direct link)
When you have seen this, you will be fascinated by the other information that is suggested.