On 17/10/16 16:30, French_Fry wrote:
We have some serious cracks in our garden which is heavy clay, I can
easily lose a 4 foot cane down them! I should add that this is in SW
France and not UK, but the question I have is still valid. We have
cleared a huge amount of wood and greenery over recent weeks, mostly
from a huge laurel hedge and several fir and fig trees, the wood is
not really suitable size for burning so it has been going to the
local dump. We are thinking of buying a good quality shredder so that
most of it can be shredded and thus make it easier to dispose of.
However I had a brainwave (I think), why not shred it and feed it
into the huge cracks in the clay? it may be time consuming but i
thought it may kill two birds with one stone, namely save me trips to
the dump, and getting some organic matter into the ground, we have
around 3000 sq metres so there are plenty of cracks to fill.. is this
a reasonable idea?...

The first question I would ask is why is the clay so badly cracked? In
my experience (gardening on clay in the south of England), deep cracks
in clay are a result of the clay drying out. This is usually the result
of drought, often compounded by tall trees extracting more water from
the ground than can be replenished by subterranean water movement.

When you fill up cracks in dry clay with something non-compressible,
when it finally rains and the clay expands you will get heave. In what
direction that heave goes should exercise your thoughts. If it moves
towards buildings you might be in trouble, as unless designed with
heave-proof foundations they could move.

By all means shred the trees, but spread the shreddings on the surface
rather than under it. A good mulch will help prevent the soil drying out
in future, and as it slowly decomposes will add nutrients to the soil.

--

Jeff