We know a person that puts a certain kind of fertilizer on his lawn. The
fertilizer kills what he calls "crab grass" and turns it yellow-brown, while
the rest of the lawn is still green. So this guy always has a lawn full of
large, round, yellow-brown spots. He claims he must kill the crab grass
this way, then plant new grass seeds in the yellow-brown spots.

What is the best way to handle this "crab grass" problem?