Iron Sulphate: Liquid vs granular

We often get asked about the practical and nutritional differences of using liquid and granular forms of iron sulphate in professional lawn care, it’s an interesting question and often makes for a lively debate!

Which type is better for avoiding staining?

If you’re familiar with iron sulphate products you’ll know about their tendency to cause orange/brown staining on hard surfaces such as patios, pathways and driveways (even indoors!). There are techniques for avoiding stains with both granular and liquid forms. If using a granular you are advised to blow/brush stray granules off of these surfaces after application. The application of liquid products tends to be easier to control, for this reason, it is the current preferred choice of most of the largest lawn care providers in the UK.

Experience will eventually guide you to a preferred choice, but if pushed then liquid is a sensible choice. By its nature, the amount of iron sulphate actually applied is much less meaning that staining will be less severe and it can be rinsed off of hard surfaces with a hosepipe when accidents happen.

Which is better for greening up the lawn?

The answer to this question differs depending on the effect you are after! If you want fast green-up that is visible within hours then a liquid application is ideal but it will not last more than a couple of weeks. If you are looking for something a little longer-lasting, perhaps 4-6 weeks, then a granular treatment is better suited.

Which is better for moss control?

The most interesting difference between granular and liquid iron sulphate are the different effects they have on moss. Liquid applications tend to be very light and may only blacken the top layer of very thick moss, in many cases it’s advisable to scarify first and then apply your liquid treatment to hit any remaining moss. Granular treatments are heavier and will easily blacken the lower sections of thick moss. They will need up to 2 weeks to take effect but will do a much more thorough job. You should be slightly more careful with granular, use the correct application rate to avoid scorching and damaging the biology in the soil too much.

Find out more about iron sulphate and scarification in our other blog post: Should I apply iron sulphate before or after scarification?

Which do you prefer to use?

Many are happy with the staining risks of granular but prefer its strength and longevity, others value the liquid for its light application and it’s lower staining risk. Getting experience with both types is the best way to find out which is the best method for you. Both options are available with SmartLawn fertiliser products, if you are unsure about any of them please get in touch with a sales team member and they will be happy to advise.

Granular applications of iron sulphate Liquid applications of iron sulphate
Black & Green 12%Fe 5%MgO

First and Last +6%Fe / +8%Fe

Liquid Iron 6%Fe +1%Mn +2%N

Soluble Iron 20%Fe

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