Using Ferrous Sulphate
I love soluble iron. Also known as iron sulphate, ferrous sulphate and sulphate of iron, it gives a wonderful green up without extra mowing. It also helps keep the grass healthy throughout the cooler months.
Iron Sulphate for a Green Up
As a ‘green-up’ for turf a typical ferrous sulphate product* containing 20% iron would be mixed with water at the rate of 50 to 150 grams to treat 100 square metres of lawn. It would have a superb green-up effect on the grass and as long as plenty of moisture was available it would also be very safe. This means you can use iron sulphate at these concentrations pretty much any time of year as long as good soil moisture is available and there is no strong sun or heat.
Iron Sulphate for Hardening & Disease Resistance
Increase the concentration to 150 to 200 grams and not only will it have a good green-up effect but it will also start to ‘harden’ the turf making it more resistant to disease and fungal attack. This is a very common practice on sports turf in late autumn and winter.
At this concentration blackening of the moss will start to occur and unless conditions are on the cool side with ground moisture available it may cause some slight but temporary damage to the grass as well. I suggest you only consider applying between September and April when plenty of moisture is available and there is no likelihood of strong sunshine.
Iron Sulphate will Blacken Moss
Were you to do a repeat application (double dose) at the turf hardening rate or just increase the concentration to 400 to 500 grams not only will it green the grass and harden the turf but you will severely blacken moss. If you apply at this rate ensure cool wet conditions to aid penetration into the moss and reduce any possibility of temporary damage to the grass.
The maximum safe limit for ferrous sulphate is 500 grams per 100 square metres in at least 5 and preferably 10 litres of water. This strength is perfectly safe for the grass in cool wet conditions.
Mixing Iron Sulphate
Iron sulphate dissolves quite readily. As you will generally be mixing in the cooler months I suggest adding a little warm water to speed the dissolving process. Once mixed use it within a day or so as the iron will start to oxidise thereby losing its efficacy. It won’t work very well either!!
If you're using a watering can to apply to the lawn use a Weedkiller Sprinkle Bar* for even application. As with all soluble products (like salt) it can be difficult to dissolve the last grain, therefore, I suggest when mixing your solution, mix in a bucket, let it settle for a minute, then pour it into your watering can leaving a cupful of the undissolved dregs in the bottom of the bucket. This will prevent clogging of the holes in the sprinkle bar.
For application procedures see Soluble Iron Application