foaming

Haven't run the tractor in a couple months, started it up and I've got fluid everywhere. What is this overflow/blowoff hose behind the engine?

I was pulling a bush hog and the power steering started to shake. I turned around and went back to the barn. when I got there, the three point hydraulics wouldn't lift the bus hog. I checked the transmission oil level and it was way low. I put about 9 gallons of fluid in it. Now (and probably...