Re: CULT: clay & soil structure

I agree with John Bruce's comments about stress, rot, heavy rain, and
clay soil.

To answer Linda B in Detroit Michigan about clay, I will have to dig out
my text book to make sure I don't make too many mistakes.

We've talked about soil texture, which is the size of the individual
soil particles (sand is the biggest, silt in the middle, clay the
smallest).  And I described soil aggregates which are the bigger
particles formed when organic matter sticks sand, silt, and especially
clay together into semi-stable bigger bits (usually sand sized).

There is a third factor, soil structure, that affects how well soil is
aerated and what happens in heavy rainfall.  If you dig up a shovelful
of undisturbed dirt (not mud) and dump it on the ground, it will break
apart in fragments that are related to the natural structure of the
soil.  Soil with a lot of gravel or sand has little or no structure,
soil with a lot of clay does have structure <unless> it's been tilled
and/or compacted.  Tillage breaks down structure.  Compaction from human
traffic usually only affects the surface layers.

Now that I've written all that, I'm not sure what use it is to the
average gardener <g>.  Except that maybe you've wondered why heavy rain
pools on top of soil that's been tilled and compacted by walking on it,
but not the same soil where it isn't tilled and compacted.

--
Linda Mann east Tennessee USA zone 7/8
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