Garden Rant pointed me to a great article on soil in National Geographic.
Garden Rant: "It turns out all that babying of the backyard dirt IS important. Do not miss Charles Mann's terrific piece in September's National Geographic about good soil, a natural resource that is disappearing all over the world at an alarming rate. The accompanying slide show is pretty great, too."
Try the soils quiz. I did so before reading the article and got 3 out of 10 correct on the quiz. "You may want to try again," it says.