Iron fertilizer is said to help reduce moss in the lawn. Read here when you can save the money for iron fertilizer and how a shortage occurs.
In the spring, the moss in the lawn often seems to have increased again. In search of solutions to this problem, every lawn owner sooner or later hears about the possibility of getting rid of moss with iron fertilizer. We create clarity in the tangled mossy carpet of dangerous half-knowledge, well-intentioned advice and real expertise.
Iron is an essential nutrient for all plants. In the following we would like to explain to you why lawns need iron, whether iron fertilizer fights moss in the lawn and how you can recognize an iron deficiency. We then go into how iron deficiency can develop and when iron fertilization is necessary - there are usually much better alternatives.
You can find general information about lawn fertilizers in our special article.
Why does the lawn need iron?
Lawn grasses - like any other plant - need the 14 essential nutrients to be able to survive and reproduce. In addition to the main nutrient elements nitrogen (N), phosphorus (P) and potassium (K), magnesium (Mg) is also absorbed by the lawn in large quantities. Iron (Fe) is one of the trace nutrients. These are only absorbed in the smallest amounts, but are no less important than the main nutrients. Iron, for example, plays a key role in controlling enzyme activity in plants and thus also enables the formation of proteins and green chlorophyll. The plant also needs it to regulate cell respiration, which produces energy from carbohydrates.
Tip: Many lawn fertilizers contain the trace element iron and advertise its content. In fact, however, iron is the most abundant nutrient in soil. It is extremely unlikely that a deficiency will occur because the lawn has removed all of the iron present from the soil: after all, iron only makes up about 0.01% of the dry plant mass on average.
Iron fertilizer against moss in the lawn
In quite a few people, as well as in internet forums, there is a rumor that moss in the lawn can be combated with iron fertilizer. In fact, a certain effect can be achieved with the application of iron sulfate (FeS04): The reaction of FeSO4 in aqueous solution is acidic. The application can achieve a very rapid pH change in the soil, which is poorly tolerated by the moss plants. As a result, they die and can be raked out. However, this effect is short-lived. Due to the acidification of the soil under the lawn, the moss has an even easier time of it the next time. And the constant application of iron sulphate and lime alternately is not a solution either: an accumulation of calcium, iron and sulfur in the soil sooner or later leads to excess symptoms in the lawn.
A long-term solution to moss displacement is just changing the contributing factors: waterlogging, soil compaction, shade, lack of or incorrect fertilization and the choice of an unsuitable lawn seed mixture cannot be remedied by spreading large amounts of iron fertilizer - even if some Vendors of the generous 10 liter buckets like to have you believe that.
Detect iron deficiency in lawns
An iron deficiency manifests itself as chlorosis (yellowing) of the stalks. What is special about iron deficiency is that the leaf veins remain green longer than the area in between. In addition, the symptom always appears on the youngest stalks first - unlike nitrogen deficiency, which affects the older stalks first. In order to differentiate between an iron deficiency and a nitrogen deficiency, you have to look very closely. A severe deficiency can even result in a whitish discoloration.
Reasons for iron deficiency in lawns
The most common reason for iron deficiency is not the absence of iron. If there is no lack of iron, even normal iron fertilization has no significant effect on the nutritional status of the lawn.
Iron is present in the soil as a trivalent and as a bivalent iron ion. Plants usually only take up iron as the divalent ion (Fe2+). The two ionic forms are in a chemical equilibrium with each other, which can shift: If the soil is rather acidic, there is a lot of Fe2+ and there will definitely not be a deficiency.
If the pH is high, on the other hand, there is more Fe3+ that cannot normally be absorbed. Itcan lead to a relative iron deficiency. However, grasses possess a strategy that is unique in the plant kingdom: they form mugeinic acids, which have a very strong attraction to Fe3+. These mugeic acids are transported out of the roots and into the root space where they bind to Fe3+. At the same time, special transport channels are built up in the outer cells of the root, which are specialized in absorbing the iron ions together with mugeic acid. Grasses are therefore able to absorb iron when the pH value is actually too high. However, because this physiological adaptation costs a lot of energy, it is only possible if the plant can operate an active metabolism to generate energy. For this reason, anything that inhibits the life processes of the lawn can lead to a relative iron deficiency when the pH of the soil is too high. In the table below we have summarized for you what causes a relative iron deficiency in lawns and what you can do about it.
| What leads to relative iron deficiency | Solution |
|---|---|
| Waterlogged or compacted soil | - Regular scarifying, aerating, sanding (maximum once a year) - Never fertilize with sulphur, as this binds Fe2+ so that it is not available - Long-term: fertilize organically, to keep soil loose and well aerated through humus formation |
| Dry soil that does not retain water well | - Long-term: Organic fertilization to improve water storage capacity through humus formation |
| High pH calcareous soils | - Use of acidic fertilizers (e.g. ammonium sulphate), water only with rainwater, regularly spread acidic materials - e.g. compost from rhododendron leaves, coffee grounds, coniferous wood and ammonium |
As a rule, therefore, only a relative iron deficiency occurs in lawns. However, in special locations where no iron can form from the parent rock through weathering, there can also be an absolute deficiency. Raised bog soils and peat substrates do not contain any iron reserves. In the rare event that your lawn grows on such a substrate, iron fertilization may be appropriate.
Tip: Generally difficult living conditions can therefore cause a relative iron deficiency in lawn grasses, although there is iron in the soil. You can prevent an overwhelmed lawn by using a lawn-seed mixture that is suitable for your location from the start. Here we have forYou put together which type of lawn makes sense when!
Iron fertilizer for lawns: use and application
On a he althy soil with a normal pH value, iron fertilization can be done with ferrous sulphate. Sulfur and iron ions dissolve in water and can be absorbed by the plants. However, when there is a lack of oxygen due to waterlogging or soil compaction, they also like to come together again and are then difficult to dissolve. Fetrilon® is a compound fertilizer with many micronutrients. It contains several trace elements in a special, soluble compound. Radigen® is also a fertilizer with several trace elements, which has a gentle long-term effect. In the case of severe and acute deficiency, iron(II) sulfate, iron chelates or iron citrate can be applied as foliar fertilizer.
Please note: Iron(II) sulphate has a corrosive effect on skin and mucous membranes due to its acidic reaction with water. Animals as well as humans can be severely damaged if they are touched or even swallowed. A lawn treated with iron (II) sulfate should not be walked on for at least 24 hours and should also be as inaccessible as possible to wild animals and domestic animals. In addition, granules worn on shoes or paws on the pavement lead to rust stains on many materials. These stains can only be removed with even stronger acid.
Iron Fertilizer for Lawns: Benefits & Alternatives
In summary, iron fertilization is not necessary in most cases and has no effect. A general improvement of the soil, on the other hand, reliably helps to prevent iron deficiency. With organic lawn fertilization, for example, this is still possible without any problems long after the lawn has been laid. Our Plantura organic lawn fertilizer and our Plantura organic autumn lawn fertilizer are certified organic and come with everything you need to keep your soil and lawn he althy and the iron available.
In this special article you will find general information about organic lawn fertilizers. This article also provides information about organic lawn fertilizers.