Nitrogen vs Iron for Lawns (what to use and when)

When springtime rolls around, everybody eagerly tries to green up their lawn. But not all products affect lawns the same way. Understanding how nitrogen fertilizer and iron amendments affect your lawn is essential for knowing what to use on your lawn, and when to use it. In today’s article I’ll compare Nitrogen vs Iron for lawns, and explain how each product works and help you determine what your lawn will benefit most from.

Why Use Nitrogen or Iron on Your Lawn?

Both iron and nitrogen issues cause a lackluster, yellow, or pale green color in lawn grass. Both Nitrogen and Iron can help your lawn green up and look healthier.

Knowing how each product works to green up your grass will help you understand which product is best to apply to your lawn.

In this article, we’ll discuss how nitrogen vs iron lawn products affect lawns differently.

While most lawns benefit from an application of both nitrogen and iron, each addresses separate issues with your lawn, so understanding what your lawn actually needs may save you some money.

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Could Your Lawn Use Iron?

Let’s take a closer look at amending your lawn with iron – why grass needs iron, how it helps, and how to tell if your lawn needs it.

Why Does Grass Need Iron?

I’ll discuss how to tell if your lawn is iron deficient in a moment. First, let’s go over what iron does for your lawn.

Plants use iron to make chlorophyll, which is in turn used for photosynthesis, or the process of converting sunlight into nutrients.

Grass lacking in chlorophyll will end up having a yellowish tint. This is especially evident in young grass.

If the younger parts of the grass are almost white, your plant (in this case your grass) may have very severe iron chlorosis.

Remember that the green color of grass is caused by chlorophyll. So if you notice your lawn has a pale color or is yellow, there is a problem with its nutrients and conditions.

It might need iron.

Signs of Iron Deficiency

The first sign of an iron deficiency is usually a light green color on the top of your grass blades. The lower levels of the grass will probably be darker.

Iron deficiency may only affect certain areas of your lawn, as well.

A common characteristic of iron deficiency is that your lawn looks almost like it has been painted a lighter color. When this happens, your lawn probably has iron chlorosis.

Severe iron chlorosis is a serious threat to your lawn. The tip of the grass leaf starts to become yellow, then the problem travels further down the blade.

How to Tell if it’s Iron Chlorosis or Something Else

It’s worth noting when diagnosing your issue that while many types of deficiency or disease can lead to yellow leaves in grass, iron chlorosis will exhibit green vascular staining.

You can recognize this when the veins are still green, but the rest of the plant is yellow. Here’s an example on a larger plant leaf (you can look for similar presentation on grass blades):

How to Test for Iron Deficiency

If you’re uncertain whether you have an iron deficiency or nitrogen deficiency in your lawn, try adding a small bit of nitrogen to a limited part of the lawn, to test the result.

When buying fertilizer, avoid ones with both nitrogen and iron in one bag, unless you know your lawn needs both (if that’s the case, buy Milorganite … you can read why it’s my favorite here, and how often to apply it here).

Only Iron Can Fix Iron Deficiencies

Applying a product that only has iron, and no nitrogen, is essential. To fix an iron deficiency, buy ferrous sulfate powder. Stay away from ferrous ammonium sulfate, as this type of fertilizer contains nitrogen.

Ferrous sulfate should be applied either as a lawn amendment in granule form, or as a spray solution.

Personally I use an iron amendment called Dr. Iron (Amazon link) to maintain a rich, dark green color in my lawn, though I’ve used Ironite in the past.

I prefer Dr. Iron now because it doesn’t stain my concrete walkways the way some other Iron products do.

If you decide to buy a powdered ferrous sulfate (here’s one on Amazon), to mix and apply it to your lawn, you need to:

• Mix one teaspoon of ferrous sulfate into a half-gallon of water.
• Using a garden sprayer, spray the solution over an area of your lawn about 15 feet by 15 feet.

Make sure that every drop of the solution is applied. Allow the solution to sit on the grass for a full 24 hours before doing further maintenance, such as irrigating or mowing.

Don’t Apply Nitrogen to an Iron Deficient Lawn!

If your lawn has an iron deficiency, applying nitrogen may only worsen the problem.

Even though nitrogen can green up a normal lawn, or a nitrogen-deficient lawn, it won’t help an iron-deficient lawn.

If your lawn has severe iron chlorosis, adding more nitrogen will whiten the leaves, and may eventually cause your grass to die.

Don’t Guess … Test (your soil)

I recommend testing your soil every spring to get a good understanding of what your lawn has, and what it needs. Doing so will allow you to save money and get better results.

Instead of guessing what your lawn needs, you’ll enter the season knowing exactly how to unlock your lawn’s potential.

I use this kit from Amazon, which allows you to mix soil samples from different parts of your yard and provides accurate results from a lab in an easy-to-use online dashboard.

It’s the best money I spend every year and I can’t recommend it highly enough.

And if you’re interested in taking the guesswork out of what to do next after you get your soil test results, consider Sunday’s subscription lawn-care plan. They test your soil for you and use local weather data to send you exactly what your lawn needs, when it needs it. It’s pretty fool-proof – you can Click Here for Your Instant Lawn Analysis and take 15% off your order with promo code LAWNCHICK2024.

Long-Term Fixes for Iron Deficiency

Adjusting your soil’s pH level fixes iron deficiencies over the long term. Soil that’s too alkaline can cause iron deficiency.

Soil compaction and high phosphorus levels also cause iron deficiencies. Cold weather is another potential cause. Cold temperatures affect microbe activity and interfere with iron uptake.

A very dry or even excessively wet lawn could also cause iron deficiency.

Adjusting Your Soil’s pH Levels

Doing a soil test will tell you the pH level of your grass.

If you find that your soil is too alkaline and you need to adjust the pH, you will have to make it more acidic.

If it’s too acidic, you may need to sweeten the soil by applying lime to your lawn. In general, a pH between 6 and 7 is best for grass.

One approach to fixing soil that is too alkaline is to add elemental sulfur. Soil bacteria naturally use sulfur. The sulfuric acid that is produced will help to bring down the pH of the soil.

Be aware, though, that this affect will probably only be temporary. After the bacteria have utilized the elemental sulfur you applied, there will probably be an increase in the pH of the soil.

Nitrogen: Why It’s Important for Your Lawn

Nitrogen is one of the three essential nutrients your grass needs for proper growth and health.

Like iron, nitrogen helps plants develop chlorophyll to conduct photosynthesis. However, nitrogen is a micronutrient and acts differently than iron.

Heavy rains can easily deplete nitrogen from your lawn, making deficiencies in this vital nutrient incredibly common.

Signs of Nitrogen Deficiency

One of the ways to differentiate nitrogen deficiency from iron deficiency is to see which area of the plant is yellowing.

With a nitrogen deficiency, you’ll notice problems with the bottom part of the blades. This is the older part of the plant and turns yellow without nitrogen.

In most cases, yellowing caused by nitrogen deficiency tends to be more generalized throughout the grass, instead of showing up in patches like iron deficiency.

Other signs of nitrogen deficiency can include:

• Difficulty recovering from stressors such as foot traffic and changes in the environment.
• Grass taking longer to grow.
• Recurring problems with disease on your lawn.

Fixing Nitrogen Deficiency

Applying nitrogen fertilizer is the best way to resolve nitrogen deficiency. However, be careful when choosing fertilizer since you can easily over-apply and end up harming your grass.

Natural, slow-release nitrogen fertilizer is best to ensure even, healthy growth of your grass. You also won’t have to fertilize as frequently with slow-release fertilizer as you would otherwise.

A good way to understand the difference between synthetic (man-made) and organic (naturally occurring) nitrogen fertilizers are as follows:

• Synthetic fertilizers feed your grass.
• Organic fertilizers feed your soil.

In my view it’s always better to feed and support soil health, because if you don’t your lawn becomes overly reliant on your synthetic fertilizers. Without getting its fix, it will never perform.

When you buy a nitrogen fertilizer, carefully read the instructions. Make sure to apply it at proper intervals throughout the year.

If you feel uncertain about how and when to do this, talk to an expert at your local garden center, or read my article on the subject.

Iron vs Nitrogen for Lawns … Why Not Both?

As we have seen here, nitrogen and iron deficiencies are two possible causes of the yellowing you see on your grass.

You don’t have to choose between nitrogen vs iron for lawns … your lawn will probably benefit from both. But understanding how nitrogen and iron affect your lawn will let you know the best way to care for your grass.

To give your lawn the treatment it needs to be healthy, homeowners must examine and troubleshoot lawns with good information, and accurate data from a soil test.

This will allow you to treat the right problems with the right products, and get the best results.