Gardening Latest and its partners may earn a commission if you purchase a product through one of our links.
If you want to grow lush green grass in the summer fertilizing regularly will be an important part of your lawn care regime. However, if you put too much fertilizer at once, or over use fertilizer over a long period, it can cause fertilizer burns.
If you over-fertilize your lawn, it can lead to discoloration and an unkempt appearance and result in parts of your lawn dieing off. We will explore what causes this to happen, possible recovery solutions, and methods to prevent fertilizer burn from happening in the first place.
The primary reason why fertilizer burns grass is because the nutrients in the fertilizer are too concentrated for the grass to handle. The roots of the grass can’t take up the nutrients fast enough, so they build up in the soil removing moisture and oxygen causing the grass blades to burn.
What Causes Fertilizer Burn?
When you apply fertilizer, as it is hygroscopic, it absorbs and takes moisture out of the ground and the soil becomes drier and less able to hold water. This is caused by an excess of nitrogen or ammonium sulfate, and other salts in the fertilizer, When there is an excessive build-up of these mineral salts in the soil, the grass dries out.
In addition to this, overuse of chemical fertilizer can reduce organic matter and humus in the soil, as well as increase acidification, which leads to a high risk of fertilizer burn which will cause stunted grass growth and eventually areas of dead grass.
The overuse of fertilizer, therefore, either in the short term or over a period of time will be detrimental to the grass, as the roots of the grass don’t get enough water which leads to yellow or browning of the grass blades that are the telltale signs of fertilizer burn.
What Are the Symptoms of Fertilizer Burn on Grass?
If your lawn begins to turn yellowish or brown this is often a sign of mild fertilizer burn. This usually happens when you use too much fertilizer but can also be caused by a gradual build-up of salts in the soil from general over-fertilizing. If you notice yellowing or browning near the roots of your grass you should look to take action immediately.
With severe fertilizer burn you will see areas of brown grass and dead spots appear with the grass blades becoming brittle and breaking easily. These areas are often referred to as “brown patches.” Again, severe fertilizer burn can be caused by either a single fertilizer application or the cumulative effect over a period of time. In this latter scenario, it would be hoped that you would have picked up on the initial yellowing of the blades and taken action at that point.
The effect of fertilizer burn can be graphically seen when you spill fertilizer on the grass, if left for any length of time it will begin to stain the green color. This is the result of a concentrated amount of nitrogen and salts being absorbed quickly into the soil.
Another minor illustration of fertilizer burn can be seen with dog urine. Dogs tend to urinate in the same spots and the grass turns yellow. This is caused which by an excess of urea in dog urine which is high in nitrogen.
Steps to Fix Fertilizer Burn
As we have seen fertilizer burns are caused by the overapplication of nitrogen and salts in fertilizers. They absorb the water and oxygen in the soil that the plant uses to support healthy root growth. When roots of grass grow into areas where oxygen and moisture aren’t present, they die and turn yellow or dark brown.
If you see signs of fertilizer burn before they get out of hand, you should look to take action straight away. You don’t want to wait until it’s too late to save your turf.
Depending on the extent of the problem there are two immediate tasks one is to reduce the nitrogen levels in the soil and secondly, add moisture and oxygen back into the soil.
Step 1 Assess the Extent of The Problem
The first thing to do is to immediately conduct a soil test to evaluate the extent of the issue you face. You can do this with soil test kits, digital soil testers, or send a soil sample to your local county extension office.
Digging up a patch of grass will give you an idea of how healthy the entire area looks. If the roots are brown or blackened, it’s likely the grass hasn’t been suffering from a lack of moisture and oxygen.
Step 2: Aerate and Prepare the Ground
Step 3: Flush Out Excess Salts
Salt is a major cause of fertilizers burning up during application. This causes problems such as soil erosion, nutrient loss, and even crop failure. In fact, there millions of cases of fertilizer burn each year in the United States alone.
Flushing out the salt will keep it away from the fertilizer, preventing further damage. Afterward, you’ll want to water the area thoroughly to ensure that the salt doesn’t wash into the groundwater. If you’re worried about runoff, apply a layer of mulch around the plants to reduce evaporation.
Step 4: Add Sawdust or Woodchip Mulch and Amendments
Whilst watering can help flush out some of the salts and wash away some of the nitrogen, it might not be enough. One of the best ways to remove nitrogen from the soil is to lay a sawdust or woodchip mulch.
Wood is an organic material that is often used as a carbon-rich material in compost piles. It loves nitrogen reacting with it and breaking down into humus. The advantage of putting down fine woodchips or sawdust is that it will help reintroduce organic matter into the soil.
If your soil test shows excessive acidity in the soil you should apply some lime to bring the pH levels back into balance for good grass growth.
Step 5: Overseed
If you have large areas of dead grass you should take the chance to overseed. New grass seeds need extra nitrogen in the germination process which is why you would ordinarily put down starter fertilizer with the seeds. In this case, however, as the soil is still likely to have excess nutrient levels and unless you have successfully flushed out the excess nitrogen, you will be able to do so without adding any more fertilizer.
If the over-fertilization is particularly bad and the nitrogen levels are too high, you will have to wait before overseeding, continuing to test the soil until the levels become acceptable.
Step 6: Allow Grass to Grow
At this point, you will then have to leave it and wait for the new growth of both the existing grass and new seeds. Keep monitoring the nutrient levels of the soil and then if required add organic or slow-release fertilizer.
Then mow it down to about 3-4 inches high. Wait another month or so and let it grow back up. This process takes anywhere from 8 to 12 weeks depending on watering or how much rain there has been. Once the grass is growing well, begin to gradually reapply fertilizer if needed and water regularly and constantly monitor the nutrient levels with regular soil testing.
Preventing Fertilizer Burn in Grass
The best strategy for dealing with fertilizer burns is to prevent them from happening in the first place.
There are many ways to prevent fertilizer burn. You can choose organic fertilizers over chemical ones. Organic fertilizers contain natural ingredients like composted manure, peat moss, and fish emulsion. They will provide slow-release nitrogen, which allows the grass to absorb it slowly.
1. Remove Excess Fertilizer
As we have seen excessive use of nitrogen fertilizers can lead to salt accumulation in grassy areas. This can happen even if you do not observe excessive amounts of fertilizer being applied. To prevent salt buildup, follow these steps:
• Use a finger or small shovel to scoop up any excess fertilizer before it begins to dry out.
• Avoid applying fertilizer during wet weather conditions.
• Apply fertilizer according to the manufacturer’s instructions.
• Monitor soil moisture levels closely. If necessary, add water to maintain proper soil moisture.
2. Add Water and Aerate
Overfertilization will kill your lawn quickly. If you overfeed your lawn, it won’t grow properly. Instead of adding fertilizer to your lawn, you should water regularly and maintain optimum moisture levels in the soil which are usually between 21-40%, dependent on the soil type. This helps it recover faster.
3. Keep a Close Eye on Your Grass
Overusing fertilizer can cause problems with your lawn. If you overfeed it, it won’t grow properly, which could lead to issues like brown patches, dead spots, and even burning. This can happen because the soil isn’t absorbing enough water or nutrients.
Monitoring your turf closely is key to preventing these problems. You’ll want to check your grass every week during the growing season. Water it thoroughly and apply fertilizer according to the directions on the package.
4. Use Slow-Release Granular Fertilizer or an Organic Fertilizer
There are various types of fertilizers, organic chemical, liquid or granular. Organic fertilizers or slow-release granular are often used to feed lawns because they provide nutrients slowly over a long period of time.
They’re ideal for growing natural grass because they don’t burn plants as liquid fertilizers do. However, you can still end up applying too much fertilizer, particularly granular fertilizers. To avoid this problem, start out with less fertilizer and add more gradually.
Organic fertilizer is an alternative to granular and contains no synthetic ingredients. Synthetic fertilizers contain chemicals designed to promote plant growth. These chemicals often cause harm to human health and the environment.
Carefully Calculate the Right Amount of Fertilizer for the Size of the Area
Understanding the nutrient amounts in fertilizer is key to avoiding overuse. The amount of fertilizer needed depends on several factors including the size of the area being fertilized, the type of soil, the weather conditions during application, and the timing of the application.
When you look at a fertilizer bag, you will notice three numbers prominently displayed on the bag. These numbers refer to the NPK of the fertilizer and are typically printed on the majority of commercial fertilizer packages in the format 10-10-10. These figures provide information about the type of fertilizer’s nutrient content, specifically the amounts of nitrogen, phosphorus (potash), and potassium present.
The first number represents the percentage of nitrogen in the fertilizer. The amount of nitrogen in fertilizer increases as the percentage increases. Phosphorus and potassium concentrations are also described using percentages as units of measurement.
If the numbers are 10-10-10, a ten-pound bag of fertilizer contains one pound of nitrogen; however, if the numbers are 21-22-4, a ten-pound bag contains 2.1 pounds of nitrogen.
Because commercial fertilizers contain a wide variety of nutrient mixtures, each of which is designed for a specific application, it is critical to always read the product label to ensure that you are purchasing the correct fertilizer for the job.
Fertilizer burn is a common problem for gardeners and results when too much fertilizer is applied to the lawn or if it has been applied too late in the fall. Lawns are especially vulnerable to fertilizer burn because of the way they absorb nutrients. New grass tends to absorb nutrients very fast whilst established grass does so at a slower rate. There are different types of fertilizer for these growing phases.
If you apply too much of the wrong type of fertilizer, your lawn won’t be able to take up all the nutrients. Insead the excess salts build up in the soil and draw out moisture and oxygen which in turn makes it harder for the roots to breathe. As a result, the turf starts burning, turning yellow or brown and eventually dieing.
Depending on the extent of the problem and if caught early enough, the damage from fertilizer burn is not permanent and the grass will recover with time. However, if the damage is severe, it may be necessary to reseed the lawn.
- Cornell University: Competency Area 2: Soil hydrology
Keith has been involved in the gardening and landscaping industry fro the past 21 years. From a jobbing gardener to running his own landscaping services. He is now dedicated to bringing you the latest in gardening news.