I really like this type of grow...That is a 5 gallon bucket buried in dirt...That said; my style is 5 gallon, preferably white, bucket or pot with at least four one inch diameter drain holes (the larger the diameter the better) drilled at bottom. If your bucket is black or colored you will need to insulate with pine straw or hay because of solar heat build-up...I amend (till in) a four foot by four foot square about six inches deep with one cubic foot bag Mushroom Compost (Home Depot about $4/bag) and four tablespoons "Osmokote" fert applied evenly on top and tilled in. I live in the Carolinas and have clay soil...Read the "Osmokote" instructions; do not simply sprinkle and leave "Osmokote" on top of amended area...Bury bucket/pot 4-5 inches deep...Starting soil in bucket, for me, is composed of; one third by volume FF Lite Warrior mixed two thirds by volume with FF Ocean Forrest...No additional nutes needed just add water to the bucket and amended area.
Burying two feet is too deep IMHO...Roots for MJ and most plants w/o a tap root is 2-4 inches...If surrounding soil is loose enough the roots will grow upward to compensate and plant will reach its potential..My plant's roots will often reach beyond the amended area at the end of the season and be less than two inches deep...Pull some weeds to see what I am talkin' 'bout with regard to planting depth...FWIW