There's loads of songs about the outdoors but they are generally sung by more obscure and less fashionable artists.
Musicians in Folk, Bluegrass, Americana, Country, Irish, World Music all have a large volume of material about the outdoors, farming and country pursuits
Here's a tiny list of some that spring to mind.
Dougie Maclean - I Feel So Near (and a bunch of other songs)
http://www.youtube.com/watch?v=3y8VCk4IZsI
Van Morrison - Purple Heather, Hymns to the Silence, Pagan Streams (and a few others)
John Denver - Rocky Mountain High, Eagle and the Hawk (and a bunch of other stuff if you can take it)
Night Rider's Lament (written by Michael Burton) - recorded by a few different artists
Tim & Mollie O'Brien - Away Out On The Mountain
Big Rock Candy Mountain is a hobo's fantasy about a world where he can just sit out in the mountains and all his needs are catered for by nature. All he has to do is sit around and take what he needs with no effort on his part. For example the mountains are made of candy. Harry McClintock sings the definitive version IMHO.
http://www.lyricsdownload.com/harry-mcclintock-big-rock-candy-mountain-lyrics.html