On 23/10/2015 21:38, Chris Hogg wrote:
On Fri, 23 Oct 2015 20:08:18 +0100, "Frank Booth"
wrote:


"Chris Hogg" wrote in message
...
On Fri, 23 Oct 2015 18:00:07 +0100, "Frank Booth"
wrote:

I am planning to buy ferrous sulphate heptahydrate crystals to treat moss
on
a lawn. I've not used this in pure chemical form previously having relied
on
proprietary brands which are more costly.

So does anyone know he correct rate of dilution for this form of of
ferrous
sulphate as I will be spraying the moss with it?

Proprietary brands are also the heptahydrate; it's the commonest form
that ferrous sulphate comes in and I can't believe they'd go to the
trouble of selling any of the rarer forms, unless by proprietary
you're meaning lawn sand, or a combined feed and moss killer. The pure
stuff will be a pale blue-green, but the proprietary stuff is usually
a bit orange due to oxidation, especially if it's got damp.

Use the same dilution as the proprietary stuff.

See this http://tinyurl.com/otrsq9q and in particular:

Iron Sulphate Properties
At room temperature Iron (II) Sulphate Heptahydrate appears as a
blue/green crystalline solid. Dehydration happens at 70oC and complete
decomposition happens at 400oC. Iron (II) Sulphate Heptahydrate
dissolves in water and the molecular formula for Iron (II) Sulphate
Heptahydrate is FeSO4.7H2O.

Applications for Iron Sulphate
Moss Killer / Control - Iron (II) Sulphate is very effective at
controlling moss on your lawn. To use, apply 5-10g of solid crystals
direct to each 1m2 of Lawn. Only apply solid product when its raining
or about to rain; if not dissolve 5-10g in 1 litre of water and apply.

Hi,

I visited the Intralabs website before I posted as I will be buying
FeS04.7H20 from them. And they suggest the rate you mentioned. But go to
other websites and they recommend a much stronger solution than that for the
same product for killing moss, eg 1.4 kg to 15 L water (to treat 500sq
m.)which is over 90 gm/litre, about 9 times the top rate of concentraion
suggested by Intralabs. So I'm still confused.

http://www.thelawnshop.co.uk/online-...s-24/soluble-s
ulphate-of-iron-for-moss-control-12-detail

I suspect it's not so much the concentration in water as the area you
need to spread it over that matters. Several sites talk about
spreading it dry, when the concentration is effectively infinite,
although it's a bit meaningless to talk in those terms.

Lawnshop says 1.4 kg in 15 L has to be applied to 500 sq.m. , i.e.
2.8g per sq.m. whereas Intralabs say 5-10g per sq.m. which is several
times higher.

Lawnsmith says '500 grams per 100 square metres in at least 5 and
preferably 10 litres of water'. http://tinyurl.com/q5b492g
i.e. 5g per sq.m., rather higher than Lawnshop, and at a concentration
of at least the equivalent of 1.5 kg in 15 litres, similar to
Lawnshop.

Taking all three recommendations together, and the fact that dry
application is also recommended, I would conclude that it's not
critical. But if you're worried, go for the lower rate per unit area,
and at the lower concentration, i.e. 500 grams in 10 litres (as per
Lawnsmith preferable), applied at a rate of about 3g per sq.m. (as
approximately per Lawnshop rate), or 600 ml of that solution per 10
sq.m.

E&OE :-)

I have used a somewhat empirical treatment of about a hadful of sulphate
of iron and the same quantity of sulphaste of ammonia over about 2 sq m
of lawn. My experience suggests that the concentration applied is not
critical.

Malcolm