My husband and I are perplexed at our small patch of lawn. When we first moved here it was fine, and was just grass but now it has turned into this! Please see links for pictures. We have tried a weed killer but it doesn't seem to work too well.

Please could anyone suggest anything we can do? Any insight on what type of weed it is?

P.S. We are in Tucson, Arizona.

Thank you!

http://img20.imageshack.us/my.php?image=weeds003ft0.jpg
http://img409.imageshack.us/my.php?i...eeds004fj1.jpg
http://img146.imageshack.us/my.php?i...eeds005ut9.jpg