Introduction
This is a light blue-green powder or small crystalline granule.
It was supposedly first used for regular turf maintenance in South Africa, in 1913, as a control for weeds and moss, in combination with ammonium sulphate.
Benefits of Sulphate of Iron
- It produces soil acidity, although usually at the soil surface where it is applied as part of a fine turf maintenance programme;
- It helps to reduce and control weeds and moss;
- It encourages finer turf grass species, i.e. fescue and bentgrasses, whilst discouraging coarser species, e.g. annual meadow grass, perennial ryegrass.
- It helps to 'lock-up' soil phosphate, making it unavailable to turfgrasses. This can be of benefit if annual meadow grass is dominant and needs to be reduced;
- Worm activity is reduced for a short period of time after application;
- The incidence of turfgrass diseases is reduced;
- Grass takes on a dark green colour, although if a slight over application occurs then the grass will turn black;
Disadvantages of Sulphate of Iron
- Continued use over a prolonged period of time, as well as any over application, results in the production of a thin, open sward with poor drought resistance and a poor ability to withstand wear.
- The soil becomes dry and crumbly, especially during the summer months, making grass growth very difficult;
- Over use may lead to the condition 'Dry Patch';
- Scorching of the turf is very easy, especially if it is not watered in adequately or if it is over applied.
Usage
It should only be applied when the soil is moist and never during hot, dry spells as it will severely scorch and kill off the turf.
Sulphate of Iron is mainly used as either a turf tonic or as a means to prevent or control weeds, moss and earthworms or to assist in preventing some turfgrass diseases.
Turf tonic
In this situation sulphate of iron is typically used at 4 - 6 g/m², either on its own, or as an additive to some fertilisers, e.g. ammonium sulphate.
Disease preventative spray
At certain times of the year when humidity is high and grass growth is relatively slow, disease attacks can be prevalent- especially Fusarium patch disease. A typical application at these times is 6 - 8 g/m², which is generally applied as a spray, with the 6 - 8 grams of sulphate of iron being diluted into about 2.2 litres (½ gallon) of water.
Weed or moss control
A common general application is a lawn sand which contains the following:
- 3 parts of ammonium sulphate,
- 1 part sulphate of iron, and
- 20 parts fine sand or fine compost.
The rate of application for the above mixture is generally from 140 - 210 g/m², giving a sulphate of iron content of 6 - 9 g/m², depending upon which rate is chosen.
The mixture is usually left for 24 - 48 hours to burn the weeds / moss foliage and hopefully this results in their death, or at least reduction in overall sward content.
Where there is a high content of weeds within the grass sward, a more concentrated mixture can be applied as follows:
- 3 parts of ammonium sulphate,
- 1 part sulphate of iron, and
- 10 parts fine sand or fine compost.
The rate of application is typically 140 g/m², giving a sulphate of iron content of 10 g/m².
Great care, however, needs to be taken when using sulphate of iron at this rate due to the potential for severe scorching and death of desirable grasses.
Earthworms
Earthworms are discouraged by soil acidity. Whilst the application of sulphate of iron will only acidify the turf surface (due to the relatively low quantities applied), this still helps to reduce the potential for earthworms coming to the surface itself. A typical application rate as for the turf tonics of 4 - 6 g/m², will reduce surface activity of earthworms for about 2 weeks at a time.