Complex sentence: The sugar cane is processed in plants in Salta before sent to the rest of Argentina other countries, being the one in "San Martín de Tabacal" the most important of them.
Split into simpler sentences: The sugar cane is processed in plants in Salta before it's sent to the rest of Argentina and other countries. The plant in "San Martín de Tabacal" is the most important of them.