Chris Hogg wrote:
On Tue, 20 May 2008 17:56:21 +0100, stuart noble
wrote:

Bob Hobden wrote:
"Bob Hobden" wrote
"Dave Liquorice" wrote
, stuart noble wrote:

Unlike plaster, I don't think gypsum sets when mixed with water. Kind of
important for this application I would have thought :-)
Well building plaster is (more or less) just gypsum that has been heated
to about 150C, this drives off the water from the calcium sulfate
dihydrate to form calcium sulfate hemihydrate.

2 CaSO4 4H2O 2 CaSO4 H2O + 3 H2O (released as steam).

http://en.wikipedia.org/wiki/Gypsum
http://en.wikipedia.org/wiki/Plaster

So the gypsum is already "set". B-)


I sent a mail to British Gypsum and they have replied so...

"Agricultural gypsum is available from our subsidiary company, BPB
Formula.
Please contact their Customer Services on 01636 670249 for further
guidance."

I will contact them tomorrow and let you all know where and how much,
meanwhile this is their information...
http://www.bpbformula.com/PDF/EN/Agr...um-English.pdf

interesting it comes in 25kg, 40kg and 50kg sacks.
They said they supply Jewsons and Travis Perkins with this product. The 3
local Jewsons had no idea what I was talking about and didn't have any, the
local Travis Perkins were very helpful and found out they can order it in
but in pallet loads then it's £15 to split a pallet + £40 carriage
+.........

I then tried once again phoning Farm Supplies firms locally and also got
nowhere. Hope you have better luck!

Would gypsum be any different to garden lime for this application given
that both are alkaline?

In terms of their effect on clay, no real difference. Lime may even be
more effective. But lime will raise the alkalinity (pH) of the soil,
which you may not wish to do, although if the gypsum is from flue gas
desulphurisation in coal-fired power stations, as much is, it may well
also be alkaline from residual unconverted lime.


According to the product description, Gyproc agricultural gypsum is
alkaline. Given how difficult it seems to be to find a supplier, is
there any point?

Chris Hogg wrote:
On Tue, 20 May 2008 18:16:28 +0100, stuart noble
wrote:

Chris Hogg wrote:
On Tue, 20 May 2008 17:56:21 +0100, stuart noble
wrote:

Bob Hobden wrote:
"Bob Hobden" wrote
"Dave Liquorice" wrote
, stuart noble wrote:

Unlike plaster, I don't think gypsum sets when mixed with water. Kind of
important for this application I would have thought :-)
Well building plaster is (more or less) just gypsum that has been heated
to about 150C, this drives off the water from the calcium sulfate
dihydrate to form calcium sulfate hemihydrate.

2 CaSO4 4H2O 2 CaSO4 H2O + 3 H2O (released as steam).

http://en.wikipedia.org/wiki/Gypsum
http://en.wikipedia.org/wiki/Plaster

So the gypsum is already "set". B-)


I sent a mail to British Gypsum and they have replied so...

"Agricultural gypsum is available from our subsidiary company, BPB
Formula.
Please contact their Customer Services on 01636 670249 for further
guidance."

I will contact them tomorrow and let you all know where and how much,
meanwhile this is their information...
http://www.bpbformula.com/PDF/EN/Agr...um-English.pdf

interesting it comes in 25kg, 40kg and 50kg sacks.
They said they supply Jewsons and Travis Perkins with this product. The 3
local Jewsons had no idea what I was talking about and didn't have any, the
local Travis Perkins were very helpful and found out they can order it in
but in pallet loads then it's £15 to split a pallet + £40 carriage
+.........

I then tried once again phoning Farm Supplies firms locally and also got
nowhere. Hope you have better luck!

Would gypsum be any different to garden lime for this application given
that both are alkaline?
In terms of their effect on clay, no real difference. Lime may even be
more effective. But lime will raise the alkalinity (pH) of the soil,
which you may not wish to do, although if the gypsum is from flue gas
desulphurisation in coal-fired power stations, as much is, it may well
also be alkaline from residual unconverted lime.

According to the product description, Gyproc agricultural gypsum is
alkaline. Given how difficult it seems to be to find a supplier, is
there any point?

Any point in what? Using gypsum instead of lime? Probably not, if
you're not worried about the alkalinity, but if you're on acid clay
and want to grow lime-haters, you would want to use mineral gypsum.
Whether you can find it is another matter.


Isn't mineral gypsum alkaline as well?

Chris Hogg wrote:
On Wed, 21 May 2008 12:13:10 +0100, stuart noble
wrote:

Isn't mineral gypsum alkaline as well?

I don't think so, but I may be wrong of course. From my school
chemistry, lime is not quite so strong an alkali as sulphuric acid is
an acid, and the resulting 'salt' (gypsum) ends up slightly acidic
when dissolved in water, even though the stoichiometry is satisfied
(i.e. there is no chemical excess of sulphuric acid). But I've not
actually tested it, for the simple reason I've not come across any,
although I confess I haven't exactly looked hard.

Gypsum used to be recommended for use on clay soils where ericaceous
plants (rhododendrons, azaleas etc.) were grown. These plants cannot
be grown on alkaline soils because some trace elements, notably iron
and manganese, are relatively insoluble at high pH's, and are thus not
available in sufficient quantity for the needs of those plants, and
they become chlorotic with yellowing leaves.

Gypsum would not have been recommended if it were alkaline. But that
recommendation comes from the days when most gypsum was mined or
quarried. Nowadays, the gypsum formed from desulphurisation of flue
gases with lime is widely available, almost a dump material, and is
consequently much cheaper than mined gypsum, and AIUI killed off most
of the mineral gypsum industry some years ago.


Interesting stuff. I seem to remember that clay is slightly alkaline, so
presumably soils that need breaking up aren't usually acidic. Don't
know. I'm not much of a gardener, let alone a chemist :-)

"stuart noble" wrote in message
...
Chris Hogg wrote:
On Wed, 21 May 2008 12:13:10 +0100, stuart noble
wrote:

Isn't mineral gypsum alkaline as well?

I don't think so, but I may be wrong of course. From my school
chemistry, lime is not quite so strong an alkali as sulphuric acid is
an acid, and the resulting 'salt' (gypsum) ends up slightly acidic
when dissolved in water, even though the stoichiometry is satisfied
(i.e. there is no chemical excess of sulphuric acid). But I've not
actually tested it, for the simple reason I've not come across any,
although I confess I haven't exactly looked hard.

Gypsum used to be recommended for use on clay soils where ericaceous
plants (rhododendrons, azaleas etc.) were grown. These plants cannot
be grown on alkaline soils because some trace elements, notably iron
and manganese, are relatively insoluble at high pH's, and are thus not
available in sufficient quantity for the needs of those plants, and
they become chlorotic with yellowing leaves. Gypsum would not have been
recommended if it were alkaline. But that
recommendation comes from the days when most gypsum was mined or
quarried. Nowadays, the gypsum formed from desulphurisation of flue
gases with lime is widely available, almost a dump material, and is
consequently much cheaper than mined gypsum, and AIUI killed off most
of the mineral gypsum industry some years ago.


Interesting stuff. I seem to remember that clay is slightly alkaline, so
presumably soils that need breaking up aren't usually acidic. Don't know.
I'm not much of a gardener, let alone a chemist :-)

Gupsum (calcium sulphate) is often used to improve soils containing high
levels of sodium. It is not a liming agent, it has a neutral or slightly
acidic effect on soil. However by displacing sodium it will improve the
structure of soils (including clay).

Agricultural lime (calcium carbonate) takes some time to react with the
acidity of the soil. All limestones contain magnesium, but dolomite
limestones contain higher proportions.

Hydrated lime or slaked lime ( calcium hydroxide) can also be used but are
quick acting. It should not be applied at the same time as fertilisers. A
given weight of hydrated lime is equivalent to about 1.3 times the weight of
agricultural lime.

rob

George.com wrote:

"stuart noble" wrote in message
...
Chris Hogg wrote:
On Wed, 21 May 2008 12:13:10 +0100, stuart noble
wrote:

Isn't mineral gypsum alkaline as well?

I don't think so, but I may be wrong of course. From my school
chemistry, lime is not quite so strong an alkali as sulphuric acid is
an acid, and the resulting 'salt' (gypsum) ends up slightly acidic
when dissolved in water, even though the stoichiometry is satisfied
(i.e. there is no chemical excess of sulphuric acid). But I've not
actually tested it, for the simple reason I've not come across any,
although I confess I haven't exactly looked hard.

Gypsum used to be recommended for use on clay soils where ericaceous
plants (rhododendrons, azaleas etc.) were grown. These plants cannot
be grown on alkaline soils because some trace elements, notably iron
and manganese, are relatively insoluble at high pH's, and are thus not
available in sufficient quantity for the needs of those plants, and
they become chlorotic with yellowing leaves. Gypsum would not have
been recommended if it were alkaline. But that
recommendation comes from the days when most gypsum was mined or
quarried. Nowadays, the gypsum formed from desulphurisation of flue
gases with lime is widely available, almost a dump material, and is
consequently much cheaper than mined gypsum, and AIUI killed off most
of the mineral gypsum industry some years ago.


Interesting stuff. I seem to remember that clay is slightly alkaline,
so presumably soils that need breaking up aren't usually acidic. Don't
know. I'm not much of a gardener, let alone a chemist :-)

Gupsum (calcium sulphate) is often used to improve soils containing high
levels of sodium. It is not a liming agent, it has a neutral or slightly
acidic effect on soil. However by displacing sodium it will improve the
structure of soils (including clay).

Agricultural lime (calcium carbonate) takes some time to react with the
acidity of the soil. All limestones contain magnesium, but dolomite
limestones contain higher proportions.

Hydrated lime or slaked lime ( calcium hydroxide) can also be used but
are quick acting. It should not be applied at the same time as
fertilisers. A given weight of hydrated lime is equivalent to about 1.3
times the weight of agricultural lime.

rob

Makes you wonder why gypsum isn't more readily available at garden
centres etc

In article ,
"George.com" writes:
| "stuart noble" wrote in message
| ...
|
| Interesting stuff. I seem to remember that clay is slightly alkaline, so
| presumably soils that need breaking up aren't usually acidic. Don't know.
| I'm not much of a gardener, let alone a chemist :-)
|
| Gupsum (calcium sulphate) is often used to improve soils containing high
| levels of sodium. It is not a liming agent, it has a neutral or slightly
| acidic effect on soil. However by displacing sodium it will improve the
| structure of soils (including clay).

One of the things that many posters are confusing is standard
inorganic chemistry with practical soil chemistry - it is deceptive
that the terms "alkaline" and "acid" are used for soil, because they
don't mean what inorganic chemists mean by them.

Practically, "alkaline" means "with easily accessible calcium",
"without easily accessible iron" and often "without easily accessible
magnesium", and "acid" means the opposite. Don't ask me why calcium
makes iron inaccessible and, from a brief search of the literature,
don't bother about asking the experts, either - they aren't entirely
sure.


Regards,
Nick Maclaren.

In article ,
Chris Hogg writes:
|
| I don't think the presence or absence of calcium has any direct
| influence on the accessibility of iron. It's pH that does it. As pH
| increases from a low value, say 3, iron forms insoluble hydroxides.
| Ferric iron is precipitated at a lower pH than ferrous iron, but at pH
| values above 7, both are pretty insoluble. High pH soils are most
| commonly associated with the presence of chalk or dolomite, hence the
| perception that calcium is the cause, and the inaccurate naming of
| ericaceous plants as 'lime haters'. AIUI it's no more complicated than
| that.

Oh, yes, it is! Most "lime haters" will grow quite happily in soils
which are alkaline primarily from magnesium, but not ones that are
alkaline from calcium. I did a bit of chasing up on this, and the
academic/scientific papers made it pretty clear that the calcium
caused the iron to become inaccessible to most plants in some way
that magnesium doesn't.

Yes, the inorganic chemistry is as you say, but that is only part
of the story, and the rest of it is the biochemistry of chelation,
as involved in soil ecologies. And there the state of knowledge is
that it is more complicated than it appears.


Regards,
Nick Maclaren.

Hi everyone, just moved into a new house, got a really large garden, tried to dig it but its really heavy clay land!!!! I dont know much about these things but i have been told by the local expert that Agricultural Gypsum could be a way of lightening the soil and improving drainage, is this true. However no one seems to know where you can get it from.
Any help on finding any?
Thanks
Lorraine