Other chickens walk around the bale browsing around the edges of the bale, and eating the alfalfa flakes that get scratched off onto the ground by the upper chickens. Alfalfa is a very nutritious food crop. Alfalfa sends it's roots deep into the soil.
Soil or Waste Stacks. A soil or waste stack (normally just called a stack) is a drainage pipe that passes through at least one story(floor to ceiling) as a drain pipe, this also includes any horizontal offsets. Every soil or waste stack will terminate in a stack vent that leads to outside air or a vent header.
The vent stack usually runs parallel with the soil/waste stack and may either extend up through the roof or connect to a stack vent. And in this corner: a stack vent is the uppermost portion of a soil/waste stack that continues the pipe from above the highest connected fixture out the roof.