In North America, at least, agriculture led to the introduction of slavery because the Southern colonies' agricultural sector was based on the production of staple crops. When agriculture is done like this, a plantation will grow basically just one crop that it sells instead of growing lots of different kinds of crops for its own use.
In the South, plantations started off growing tobacco and rice and indigo, depending on where they were. This was hard work and free people did not really want to do it since they could go off and get farms for themselves on all the "free" land that was around. Because of this, the plantation owners needed a source of labor that was not free. They started with indentured servants but soon came to realize that slaves would be a more reliable source of labor.