i've been rebuilding my soil for several years now, expatty. we have about 1 1/2 to 2 feet of topsoil on top of hard clay and shale clay. my garden has been the last 15 feet of my yard, end to end, and was used by my fil and then myself almost every year since 1950.
unfortunately, my fil resorted mostly to chemical fertilizers in his later, infirmed years of his life. this allowed the soil to become thin and lacking structure and nutrients.
i've added a lot of peat moss, lime, and organic compost over the last 8 years, but i keep gardening in the same spot as well, so it's an uphill battle.
my best year was after i had moved out and no one grew anything for almost 2 seasons.
i have to buy some bok choy seeds, to go with 2 types of mesculun, carrots, radishes, swiss chard, and kale. keep your fingers crossed that i can sneak out early to get it done, before my orders arrive for the day.
