The point is not over your tractor, individually. If you were living under marxism, society would have decided "all [farming equipment, factories, whatever] are the property of the community and you cannot own them individually". You couldn't lease your tractor, because you couldn't own the tractor to begin with.
Markets largely still exist in socialism we see today because capitalism is extremely pervasive. A socialist state currently is forced to behave like a capitalist entity to at least the outside world, or they will be taken advantage of by capitalists. Because of this, all socialists states today are internally capitalist with some social programs, as opposed to fully Marxists.