six of them
22000 tons
About a ton.
they fertilize the soil
volume of soil needed = 38*5*1=190sq ft .12" = 1 feet
black soil
40 yds
well i would put about 5 gallons of soil in there, maybe a tiny bit less so it does not overflow.
bongu soil
Earthworms enrich the soil with their waste, providing it with much needed nutrients.
It is 72 cubic feet.
That depends on the plant type. Also using hydroponics, no soil is needed.
Silty.