More than any other European colonists which group sought direct control over Indians who labored in their mines or their fields?

During the Age of Discovery (or, Exploration) in the 15th to 18th centuries, it was Spain that, more than any other European colonizing nation, sought (and achieved) direct control over Native Americans who ended up laboring in mines or in fields controlled by Spanish authorities. This control was the direct result of several factors, with perhaps the most important being the remarkable richness of Central and South American in respect to resources most valued during this age.