Healthy lawns have a lush, green appearance with no bare spots or signs of pests.
Nutrient deficiencies in lawns cause slowed root growth and discoloration in the grass blades.
Iron is one of the most vital nutrients for grass lawns because it aids in nitrogen metabolism and chlorophyll synthesis.
Alkaline soils are prone to iron deficiencies, which causes the grass to turn pale yellow.
Liquid iron supplements are typically used to correct the deficiency, but is it possible for grass to have too much iron?
Too much iron in a lawn disrupts chlorophyll production and will kill the grass if left untreated. The excess iron will cause your grass to turn very dark green or black and lower the pH in your soil. Improper iron supplementation typically occurs when the soil is not tested before application.
It is crucial to test your soil before using fertilizers or nutritional supplements to avoid applying the wrong amount.
Additional nutrients usually improve the health of your grass, but too much of a good thing will have damaging effects.
Read on to learn how to spot the signs of too much iron in your grass and how the issue may be corrected.
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Signs Your Lawn Has Too Much Iron
If excess iron levels in a lawn are not corrected, the grass will become too damaged to repair and begin to die.
The damage from excessive amounts of iron in your grass increases during hot weather.
This means your lawn may have too much iron in the spring, but the damage will not be noticeable until temperatures increase in the summer.
There are several visual signs your lawn is suffering from too much iron.
Getting a soil test to confirm iron levels is always recommended before taking steps to correct the problem.
The symptoms of excess iron content in the grass will sometimes mimic those of fungal diseases.
Dark Green or Black Grass
The most notable sign your lawn has too much iron is the appearance of dark green or black grass.
Iron plays a significant role in controlling respiration, metabolizing nitrogen, and synthesizing chlorophyll in plants.
Nitrogen is essential for healthy root growth, and chlorophyll gives grass its green color.
Many homeowners apply iron sulfate to their grass for a green lawn.
Some herbicides use iron as an active ingredient to kill moss and mold.
Iron applications are often used to keep fescue and bluegrass green during hot weather without increasing the excessive foliar growth caused by using nitrogen fertilizers.
When chlorophyll synthesis is interrupted, the grass blades absorb more than they are normally able to process.
The extra chlorophyll stored in the grass will make it appear dark green, black, or purple.
In alkaline soil types with a high pH, the dark black-green color will fade within a few days, and the grass will return to its normal color.
However, in most cases, iron levels in the grass will need to be lowered by other means.
Low Soil pH
Soil types with a low pH come with their own set of problems, and they will cause your grass to turn brown.
Liquid iron applications will instantly lower your soil’s pH by up to three points.
Low pH in the soil makes it more difficult for the excess iron content to be absorbed and released.
If the soil pH is not raised, excess iron will linger in the grass and cause severe damage.
Light Brown or White Discoloration on Grass Tips
Although it is a rare symptom, high iron concentrations in your lawn may cause the grass blades to turn light brown or white at the tips.
This phenomenon mainly occurs in temperatures above 80° degrees Fahrenheit (27° C).
Heavy rainfall in the summer months will also increase the likelihood of your grass becoming lighter on the tips.
The grass blade tips become lighter in color because they are burned from suddenly drying out.
Adding water to grass when it is overloaded with iron may dilute other vital nutrients needed for healthy growth.
Without these essential nutrients, it will be challenging for your grass to recover from the damage caused by too much iron.
Testing Iron Levels in Your Soil
To ensure the iron levels in your lawn, you must have your soil tested.
The two most accurate types of soil testing are the soil pH and the soil content tests.
A soil pH test is relatively inexpensive and easy to perform.
Chemical test strips cost a little more than probe-based meters, but they tend to be more accurate.
You will get better results by testing moist soil when using a probe-based meter.
If your soil has a pH lower than 5.5, your lawn likely has a high iron content.
Very few other lawn issues will cause such a drastic drop in soil pH.
When the soil pH test results are higher than 5.5 but lower than 7 and your grass is very dark, your lawn may contain too much iron.
However, in this instance, the soil pH is still high enough for your grass to recover on its own.
If you are still unsure about the iron concentration in your lawn, you may contact a lab to conduct a thorough soil content test.
A soil content test is more expensive than a soil pH test, and it may take 1-2 weeks to receive your results after the soil sample has been sent to the lab.
Further Reading: Using Ironite to help your lawn
How To Lower the Iron Levels in Your Lawn
Once you have confirmed elevated iron levels in your lawn, it is often difficult to correct the issue.
Excess iron does not break down easily in most soil types, but there are several ways to neutralize the effects to help your grass recover.
Lime decreases the high acidity in the soil caused by too much iron.
A pelletized lime lawn supplement, such as this one, may be applied to your lawn with a drop spreader.
Always follow the instructions on the label of the lime supplement to ensure you apply the correct amount.
Adding too much lime to your soil will make the pH too alkaline.
Alkaline conditions inhibit the ability of your grass to absorb other primary nutrients like nitrogen and magnesium from the soil.
Never spread lime on extremely dry or wet soil or if there is a threat of frost.
Applying lime to frozen soils increases the risk of runoff, which could harm the environment.
Using lime on your lawn during extreme temperatures in the summer increases the risk of burning your grass.
Fall and late spring applications of lime are recommended.
Bicarbonate products are not as effective as lime in raising your acid soil’s pH, but they are useful in emergency situations.
If you accidentally spill a liquid iron supplement on your lawn, adding bicarbonate will help to neutralize any adverse effects.
Always use a bicarbonate product like this one, which is specially formulated for use on lawns.
Follow the bicarbonate packaging label instructions to correctly mix the solution before application.
Never use a household baking soda product, as it may increase the damage to your grass.
After adding lime or bicarbonate to the soil to increase the pH levels, it is recommended to apply a zinc supplement.
Zinc slows iron absorption in your grass, lessening the harmful effects caused by too much iron.
Adding zinc to your lawn increases the chance of the excess iron being washed away by rainfall or water before the grass can absorb it.
Never apply more zinc than the recommended amounts on the product label.
Too much zinc will cause toxicity in grasses and other plants and stunt their growth.
Standing water on your lawn allows the excess iron to stay close to the soil’s surface.
Compacted soil will not allow moisture to drain through it properly, creating puddles and leading to poor root development in the grass.
An iron supplement will stay in these wet spots on the soil surface, where it will continue to damage the grass.
Gutter downspouts facing your lawn will also add more water than your soil can absorb.
Improving drainage in your soil allows excessive amounts of iron to dissipate into the ground.
As the iron washes down into the soil, the concentration of the mineral is lowered to a less harmful level.
There are several effective methods of improving soil drainage.
A common way to improve drainage is by incorporating organic matter like compost or manure into the soil.
Adding organic matter to the soil improves drainage by increasing the pore sizes in the structure of the soil.
Regular lawn aeration prevents soil compaction to increase drainage as well.
Another method to improve lawn drainage is installing a French drain.
Installing a French drain is somewhat expensive and time-consuming, but it is the most effective way to divert excess water away from your lawn.
Preventing High Iron Levels in Your Lawn
If you plan to apply an iron supplement to your lawn in the future, it is essential to do it safely.
Prepare your lawn before adding iron by adjusting your soil’s pH and improving drainage.
Test your soil’s pH and make the proper amendments if it is too acidic or too alkaline.
Keep in mind the iron supplement will lower the pH of your lawn almost immediately, so you may want the soil to be more alkaline to begin with.
To avoid soil compaction, it is recommended to aerate your soil at least twice yearly.
Inspect your lawn after periods of heavy rainfall or watering to see if any puddles of standing water have formed.
Puddles of water on your lawn indicate a drainage issue that needs to be remedied.
Choosing a chelated iron product like this one lessens the chance of adding excessive amounts of iron to your grass.
Chelated products are much safer to use than iron sulfates and are less likely to cause lawn damage even when the iron application is done incorrectly.