Shhh the secret formula for the organic gardening pre plant mixture

Jim has been kind enough to spill the beans and give us the base formula for the preplant mix::

If you can't find the Pre-Plant mix, just mix your own. You need to
use lime if your annual rainfall is more than 20", and gypsum if it's
less than that.

Mix 5# lime or gypsum, with 1 ounce boron (Borax), and 4 ounces
magnesium sulfate (Epsom Salt).

Use two parts of this and one part Weekly Feed mix in your beds,
mixed with the soil before planting.