I found a cactus in a 10 gallon pot that someone was giving away for free. It looks terribly beat-up. The soil is so dry it's practically petrified. I've watered it already, but I was wondering if there is anything I can do to help nurse it back...plant food, organic fertilizer?

I reall y don't know much about cacti, but I found images that looked like it could be a Prickly Pear or a beaver tail. It has no spikes on it and a couple of large ears have broken off. It's fairly tall (about 4 feet). It also has brownish spots on it that look like sandpaper.

Any suggestions?

-steve-