•Till in 3 inches of expanded shale, 6 to 8 inches deep.
•Till in 3 inches
of compost. Make sure the compost is "finished" – no green material.
•Mix the
expanded shale, compost and soil thoroughly.
•Cover with a 3-inch layer of
mulch.
If you till expanded shale and compost into clay soil, then mulch,
you should never need to add commercial fertilizer. As fully finished mulch
breaks down, it acts as a slow-release fertilizer.
You won't need to add
compost again. The mulch will gradually break down and work its way into the
soil. A year after preparing the bed, lay enough mulch on top to bring the mulch
layer up to 3 inches. In subsequent years, the mulch breaks down faster, and you
will add mulch in spring and fall to bring the mulch depth to 3 inches. Nothing
else, neither compost nor commercial fertilizer, is necessary.