I had a burr-oak tree on my country property that looked like it was dying in 1978. I pounded tree feeder spikes into the ground around it, following package directions. It looks better today, in 2009 than it looked then. I would say it looks pretty healthy--dark green leaves over most of it and not many dead or dying branches.
My dad had a sickly looking clump of birch trees in his sandy lawn. He dug around them, exposing the root ball and made a big doughnut-shaped pit about two feet deep around it. He filled the pit with composted cow manure and a little soil. The birches perked up and looked great for another 12-15 years, although they sagged again after that and he didn't re-dig (a big project).
p.s.: I'm not sure what the date was on this question I'm replying to. Maybe very old.
I wish the date could display when we are in "reply" mode. SYSOP?