What you need to know about soluble iron sulphate

Soluble iron sulphate commonly available for use on lawns as a DIY alternative to liquid iron products. It is dissolved in water and applied with a sprayer, usually to cause blackening in moss, but also to quickly give colour to the lawn. If you are a lawn care professional then the chances are that you’ve used iron sulphate at some point in the past. In fact, many of the public have used it on lawns themselves in popular garden products without even realising it!

Iron sulphate needs mixing into water prior to use. Once made up the iron will start to oxidise and the liquid will turn brown, you should use it up fairly quickly as the oxidisation may cause problems later on. If you like the idea of keeping a liquid concentrate handy then SmartLawn Liquid Iron may be more suitable for you.

Did you know that soluble iron sulphate is available in two different forms?

You may have experienced this already and wondered why they look and act different but are sold as the same thing? It’s to do with the water content…

soluble iron 2

Mushy, green crystalline powder.

Dried Soluble Iron small

Dry, white/greenish free-flowing powder.

Both types are known as ferrous sulphate heptahydrate, and both have an iron (Fe) analysis of 20%. The main difference is that the “Dried” version has had water taken out of it by being tumbled with hot air like in a tumble dryer. This process does use more energy and time, hence the reason why this version tends to be more expensive.

The benefit of drying the ferrous sulphate is that you end up with a product that stores well and is easier to handle. However, it may need warm water to dissolve (depending on the time of year) and if not dissolved well enough it has been known to block sprayer nozzles. The “wet” version dissolves much quicker by comparison, even in cold water.

They both cause staining of patios, paths, driveways etc and should never be applied to these surfaces. Both versions are irritant to skin so it’s important to handle with gloves and be wary of how you store them (away from children and pets). We recommend using a plastic scoop to measure out the product as metal ones will quickly corrode.

Smartlawn Fertiliser Bag smallSmartLawn’s Soluble Iron contains the “wet” version of iron sulphate, over the years we have found this to be the most popular with lawn care technicians due to its low cost and high solubility.
However, if you prefer the other version please do enquire with a member of the sales team as we can supply that one too! 01963 364788 sales@greenbest.co.uk 

3 thoughts on “What you need to know about soluble iron sulphate

    • Daisy Lacey BSc (Hons) says:

      Hi Tom,
      The soluble iron we are talking about here is ferrous sulphate heptahydrate. It is 20% Fe. There isn’t any nitrogen (N), phosphorus (P) or potassium (K) in it. Does that answer your question?


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