Why is the title of the story appropriate?

It's an appropriate title for two reasons. First of all, it relates to the overriding theme of greed. The greedy Russian peasant Pahom spends all his time acquiring as much land as he can get his hands on. But somehow it just never seems to be enough. The more land he acquires, the more he wants. So this raises the inevitable question: How much land does a man need?
Secondly, the title of the story hints at the answer that Tolstoy provides to his own question. Pahom eventually dies as a direct result of his greed, exhausted after trying to gain as much land from the Bashkirs as he can traverse in a single day. For all the land that he's acquired, all the vast wealth he's accrued, Pahom can't take any of it with him into the next world. In this world the answer to the question "How much land does a man need?" is "Just enough to be buried in."