I have read the continuous discussions on amending "hardpan" described as
clay soils. I live in PNW where hardpan is described as glacial till. It is
second only to asphalt in ease of digging. I have known it as clay my entire
life. I recently attended a seminar on landslide prevention put on by the
engineering dept. of the City of Seattle. Several speakers were making a
distinction between hardpan and clay layers in the soil. I got to speak with
a soil engineer and he described hardpan as a matrix of silt and rocks left
from the glacial period. He said it is even harder than clay when dry. Yet
with enough moisture it can soften and even wash away. This reminded me of a
neighbor who bragged about getting a load of river silt that had washed
under a friends house in a flood. It looked just like gray hardpan. All
discussions I have seen describe hardpan as clay and warn about creating
cisterns in holes dug and amended with something more permeable. I think
clay is impervious to water, I have seen clay on beaches that does not
dissolve, hardpan on the other hand, will absorb water and soften. To test
if you will get a cistern, fill the hole to the top of the hardpan layer
with water. If it drains 15" of water in 12 hours an inch of rain is not
going to create a sump. To aid in digging you can add a foot of water to
the hole and return the next day to find 2-3" have softened and are easily
removed. It is slow but easier than using a 6' 14# digging bar. My personal
experience is limited to PNW glacial till if you really have clay and not
silt, the test above should disclose it.

steve stidham wrote:

I have read the continuous discussions on amending "hardpan" described as
clay soils. I live in PNW where hardpan is described as glacial till. It is
second only to asphalt in ease of digging. I have known it as clay my entire
life. I recently attended a seminar on landslide prevention put on by the
engineering dept. of the City of Seattle. Several speakers were making a
distinction between hardpan and clay layers in the soil. I got to speak with
a soil engineer and he described hardpan as a matrix of silt and rocks left
from the glacial period. He said it is even harder than clay when dry. Yet
with enough moisture it can soften and even wash away. This reminded me of a
neighbor who bragged about getting a load of river silt that had washed
under a friends house in a flood. It looked just like gray hardpan. All
discussions I have seen describe hardpan as clay and warn about creating
cisterns in holes dug and amended with something more permeable. I think
clay is impervious to water, I have seen clay on beaches that does not
dissolve, hardpan on the other hand, will absorb water and soften. To test
if you will get a cistern, fill the hole to the top of the hardpan layer
with water. If it drains 15" of water in 12 hours an inch of rain is not
going to create a sump. To aid in digging you can add a foot of water to
the hole and return the next day to find 2-3" have softened and are easily
removed. It is slow but easier than using a 6' 14# digging bar. My personal
experience is limited to PNW glacial till if you really have clay and not
silt, the test above should disclose it.

I hope Bob pipes up on this. I know that silts is measured as a
component in some soil tests, and a review of loam will show relative
proportions of silt and clay. Good points. But I do beg to differ on
whether clay will dissolve, or at least form a suspension in water. It
will or does. I thought that clay and silt were next to each other on
the continuum of particle size, with clay being the smallest.

"Cass" wrote about playing in the dirt:

I know that silts is measured as a
component in some soil tests, and a review of loam will show relative
proportions of silt and clay. Good points. But I do beg to differ on
whether clay will dissolve, or at least form a suspension in water. It
will or does. I thought that clay and silt were next to each other on
the continuum of particle size, with clay being the smallest.

Hello Cass,

I, for one, like to have a definition before we start a discussion of
what we are discussing here to avoid confusion. When I was doing
my research to become a MG I become keenly interested
in the composition strata of the different soils found in the PNW and
the term "glacial till" was used often enough to send me to the nearest
library to get a more or less exact definition. FWIW, here it is, now
available of course through Google:

"Glacial till.This is that part of the glacial drift deposited directly by
the ice with little or no transportation by water. It is generally an
unstratified, heterogeneous mixture of clay, silt, sand, gravel, and
sometimes boulders. Some of the mixture settled out as the ice melted with
very little washing by water, and some was overridden by the glacier and is
compacted and unsorted. Till may be found in ground moraines, terminal
moraines, medial moraines, and lateral moraines. In many places it is
important to differentiate between the tills of the several glaciations.
Commonly, the tills underlie one another and may be separated by other
deposits or old, weathered surfaces. Many deposits of glacial till were
later eroded by the wave action in glacial lakes. The upper part of such
wave-cut till may have a high percentage of rock fragments.

Glacial till ranges widely in texture, chemical composition, and the degree
of weathering that followed its deposition. Much till is calcareous, but an
important part is noncalcareous because no carbonate rocks contributed to
the material or because subsequent leaching and chemical weathering have
removed the carbonates. " ( to which this definition was added some time
later
according to the date from another source):

"To be soil, a natural body must contain living matter. This excludes former
soils now buried below the effects of organisms. This is not to say that
buried soils may not be characterized by reference to taxonomic classes. It
merely means that they are not now members of the collection of natural
bodies called soil; they are buried paleosols.

Not everything "capable of supporting plants out-of-doors" is soil. Bodies
of water that support floating plants, such as algae, are not soil, but the
sediment below shallow water is soil if it can support bottom-rooting plants
such as cattails or reeds. The above-ground parts of plants are also not
soil, although they may support parasitic plants. Rock that mainly supports
lichens on the surface or plants only in widely spaced cracks is also
excluded.

The time transition from not-soil to soil can be illustrated by recent lava
flows in warm regions under heavy and very frequent rainfall. Plants become
established very quickly in such climates on the basaltic lava, even through
there is very little earthy material. The plants are supported by the porous
rock filled with water containing plant nutrients. Organic matter soon
accumulates; but, before it does, the dominantly porous broken lava in which
plant roots grow is soil.

More than 50 years ago, Marbut's definition of soil as the "outer layer" of
the Earth's crust implied a concept of soil as a continuum(Marbut, 1935).
The current definition refers to soil as a collection of natural bodies on
the surface of the Earth, which divides Marbut's continuum into discrete,
defined parts that can be treated as members of a population. The
perspective of soil has changed from one in which the whole was emphasized
and its parts were loosely defined to one in which the parts are sharply
defined and the whole is an organized collection of these parts."

For those who are interested in the composition of our soil - more or less
since Oregon has some different and local characteristics as well, but I am
going to dump all the states composing the Pacific Northwest into one area -
here is a very interesting link:

http://soilslab.cfr.washington.edu/esc311
507/finalprojects/jaimeyoung/uplands.html

(Of course good old OE believes in "divide and conquer" so make sure to
put all the info in one line) Good planting, everyone, glacier till or
otherwise...

Allegra

Cass wrote:

I hope Bob pipes up on this.

I am not Bob, but am piping up anyhow :-).

I know that silts is measured as a component in some soil tests, and
a review of loam will show relative proportions of silt and clay.
Good points. But I do beg to differ on whether clay will dissolve, or
at least form a suspension in water. It will or does.

My memory from Colloidal Chemistry classes is that clay will form a
collodial suspension in water, and the one way to break this up is to
add electrolytes to the colloid. It is a memory from long ago. Also,
IIRC, this is the principle by which one washes leeks and spinach and
cilantro other muddy and leafy vegetables free of the clay and soil that
have coagulated on them as a thick colloidal suspension, by adding a
pich of salt to the wash water.

I thought that clay and silt were next to each other on the continuum
of particle size, with clay being the smallest.

I think you are right. Here is an interesting article:

http://audit.ea.gov.au/ANRA/land/doc.../tech29_01.pdf


--
Radika
California
USDA 9 / Sunset 15

steve stidham wrote:

I have read the continuous discussions on amending "hardpan" described as
clay soils. I live in PNW where hardpan is described as glacial till.

Fist of all, I think we must make it clear that'Hardpan' is not a
scientific term. It is a colloquial description of soil that is hard
and compacted. It means different things to different people in
different parts of the country.

It is
second only to asphalt in ease of digging. I have known it as clay my entire
life.

Whereas glacial till CAN have clay in it, even as a major component,
it is defined as being unsorted material of greatly varied sizes all
mised together..... tilled. Get it? When it forms rock it is called
tillite. Till is a description of the texture of various unsorted
particle sizes. It is not a type of material. Till can have any
kind of rocks or minerals present in it.

... Several speakers were making a
distinction between hardpan and clay layers in the soil. I got to speak with
a soil engineer and he described hardpan as a matrix of silt and rocks left
from the glacial period.

That could very well be true for your area, but as I pointed out
above, 'hardpan' is just a farmer term for dirt that is difficult to
plow.

He said it is even harder than clay when dry. Yet
with enough moisture it can soften and even wash away.

No doubt that this is probably the case.

... I think
clay is impervious to water, I have seen clay on beaches that does not
dissolve,

Maybe what you have seen on beaches is clay that is compacted to the
point that it is very nearly like rock.

If clay is impervious to water, how do you think potters mix it with
water to make it into pots? Water plus clay equals Mud!

A lot of us who have been stuck on clay road in the rain certain WISH
that clay did not absorb water.

The flat nature of the clay particle structure does lead to water
having a hard time moving through it. In fact highly compacted clays
can be pretty much impermeable. But water will move through clay to
some degree. And don't forget, clay soils are rarely if ever 100
percent clay. They are usually mixed with silt and sand and organic
matter to some degree and is always permeable by water to some degree.

hardpan on the other hand, will absorb water and soften. To test
if you will get a cistern, fill the hole to the top of the hardpan layer
with water. If it drains 15" of water in 12 hours an inch of rain is not
going to create a sump. To aid in digging you can add a foot of water to
the hole and return the next day to find 2-3" have softened and are easily
removed. It is slow but easier than using a 6' 14# digging bar. My personal
experience is limited to PNW glacial till if you really have clay and not
silt, the test above should disclose it.

No doubt that it is VERY hard to dig in glacial till. I feel for you.

Every gardener should do a soil drainage test ...no doubt. If your
soil doesn't drain, you must do something about it, absolutely.

On the other hand, if you actually have to dig through clay in your
yard, it will usually be in the form of rubbery mud once you are a
foot or so down into the ground. That is my experience.

Bob Bauer

In Radika Kesavan wrote:
My memory from Colloidal Chemistry classes is that clay will form a
collodial suspension in water, and the one way to break this up is to
add electrolytes to the colloid. It is a memory from long ago. Also,
IIRC, this is the principle by which one washes leeks and spinach and
cilantro other muddy and leafy vegetables free of the clay and soil
that have coagulated on them as a thick colloidal suspension, by
adding a pich of salt to the wash water.

I have, from time to time, used a product called Groundbreaker on my
clay beds. It contains 'buffered polygnosulphates' or some such
gibberish. It's meant to change the structure of clay to allow root
penetration and aeration without digging.

Of course there's no way of measuring whether it works. You take it on
faith or not at all. Here's the blurb:

http://www.multicrop.com.au/soil.htm

Daniel Hanna wrote:
In Radika Kesavan wrote:

My memory from Colloidal Chemistry classes is that clay will form a
collodial suspension in water, and the one way to break this up is to
add electrolytes to the colloid. It is a memory from long ago. Also,
IIRC, this is the principle by which one washes leeks and spinach and
cilantro other muddy and leafy vegetables free of the clay and soil
that have coagulated on them as a thick colloidal suspension, by
adding a pich of salt to the wash water.


I have, from time to time, used a product called Groundbreaker on my
clay beds. It contains 'buffered polygnosulphates' or some such
gibberish. It's meant to change the structure of clay to allow root
penetration and aeration without digging.

Of course there's no way of measuring whether it works. You take it on
faith or not at all. Here's the blurb:

http://www.multicrop.com.au/soil.htm

Fascinating. Absolutely fascinating. Thanks for mentioning it, Daniel. I
need to think about this a lot more before I can comprehend what is
beign done and what implications it has, say to soil organisms that
normally keep a soil healthy. Nevertheless, techinically, it is a very
interesting approach. Here is an interesting article about this product
that you mentioned and a few others for waterwise gardening, I have not
digested it all yet, will do so in a few days prhaps:

http://www.greenworldmag.com.au/arti...?ArticleID=271


--
Radika
California
USDA 9 / Sunset 15

FOW wrote:
Lime works too !

For ... breaking up clay?

Alas, in our area, the soil is already on the alkaline side so we cannot
add lime.

--
Radika
California
USDA 9 / Sunset 15