Too Much Fertilizer on Grass

Fertilizer is a critical component in the growth of healthy lawn grass. However, each grass type has varying fertilizer needs. Excessive fertilizer can make the soil toxic, and insufficient fertilizer can render your soil unable to sustain healthy turf. 

Excessive fertilizer in lawn soil spikes soil nitrogen and salt and causes grass blade leaf scorch. These soil changes can eventually kill your entire turf. You can fix the problem by leaching out the soluble fertilizer salts from the soil using water. In extreme cases, you may have to reseed or re-sod large areas of the lawn that have turned brown with dead grass.

Too much fertilizer on grass is avoidable, and you can correct it. We’ll show you how. 

Can you put too much fertilizer on your lawn?

The table below summarizes the fertilizer requirements of different turf grasses, including the recommended frequency of application.

Type of GrassFertilizer Application RateRecommended Frequency of Application
St. Augustine Grass1 pound of nitrogen per 1000 square feetEvery eight weeks
Bermuda Grass1.5 pounds of nitrogen per 1000 square feetEvery 6-8 weeks
Zoysia1 pound of nitrogen fertilizer per 1000 square feetEvery four weeks
Tall Fescue3-4 pounds of nitrogen per 1000 square feet annuallyEvery eight weeks
Bahiagrass2-4 pounds of nitrogen per 1000 square feet per year2-4 times per year starting from spring
Ryegrass40-60 pounds per acre in the fall50-60 pounds per acre in early springTwice per year- in the fall and early spring
Centipede grass1-2 pounds of nitrogen per 1,000 square feetBahiagrass annuallyTwice during the growing season

It’s possible to apply too much fertilizer to your lawn. It’ll lead to ‘fertilizer burn,’ whereby the excess salts in the soil and nitrogen harm or kill your turfgrass. The accumulated salts from the excess fertilizer sap water from the soil and disrupt the grassroots’ moisture intake.

Fertilizer burn is more likely to occur if you use quick-release nitrogen fertilizer. Other common reasons why you may end up applying too much lawn fertilizer include

  • Failure to follow the manufacturer’s application guidelines.
  • Applying too much fertilizer in a single spot, sometimes due to accidental spillage.
  • Failure to irrigate after applying fertilizer.
  • Poor-draining lawn soil.

Limited moisture causes grass shoots to show signs of moisture stress while the roots start rotting. Turfgrass suffering from fertilizer burn typically has yellow discoloration strips of brown, dead patches.

Signs of over-fertilized lawn

Symptoms of fertilizer burn may be noticeable as soon as 24 hours post-application, making it easy to determine if excessive fertilizer application is the cause.

Leaf Blade Yellowing/Browning

If the grass blades or their tips appear brown a day after feeding the lawn with fertilizer, over-fertilization is the most likely cause. However, these discoloration symptoms are also caused by underwatering or overwatering the lawn. 

As such, leaf blade discoloration shouldn’t be used as a standalone diagnosis for fertilizer burn.

Root Rot

If you’re using organic fertilizer such as compost and apply too much of it, the grassroots may start to rot. This occurs because the organic fertilizer is piling up faster than the soil microorganisms can break it down into usable nutrients.

The built-up undecomposed organic matter retains more water. The water retention, then, leads to poor soil drainage. The grassroots then drown and rot due to the saturated soil conditions. You can tell that grassroots are rotting if they feel soft and turn brown.

Note: Root rot is typically accompanied by mold and fungal issues as these organisms thrive in oversaturated soil conditions.

Stunted Growth

If you notice stunted growth after fertilization where there was prior healthy growth, you may have overapplied the fertilizer. 

Overfertilization will cause the root system to underdevelop. In turn, it’ll affect the grass’ ability to take in water and critical nutrients. Whereas the plant was healthy before, the poor root system won’t sustain growth, and you end up with malnourished grass. 

How do you fix over-fertilized grass?

If the over-fertilization problem is not severe, with a few noticeable spots of yellow grass, you can revive your turfgrass by watering it to leach the excess salts out of the soil. However, if the problem is at an advanced stage and most of the grassroots have died, the only fix is to replant the entire turf.

Water the Turf

Irrigating the lawn helps flush the excess soluble salts deeper into the soil and out of the grass root zone. Water flushing a day or two after over-fertilizing can be enough to revive your turfgrass. 

However, take care not to overwater. Overwatering the turf exposes it to different problems, including root rot and weak root systems.

Monitor the Turf

There should be new growth within 1-2 weeks after leaching out the fertilizer salts. If this doesn’t happen, it means that most of the grassroots were already dead when you noticed the over-fertilization problem. 

The best approach to a dead grass root system is to reseed the dead patches or replant grass on the entire lawn.

Prepare the Lawn for Reseeding

Rake away the dead grass in preparation for the new grass before reseeding or re-sodding your fertilizer-damaged lawn. Raking will enable water to seep into the soil and the roots of the new grass.

Prepping the lawn also involves shoveling away the top 2-3 inches of the soil, as this is where most of the excess salts that kill the turfgrass are concentrated. Replace it with fresh topsoil that’s rich in nutrients and is well-draining. 

Finally, lightly tamp down the new topsoil before leveling it out with a rake.

Plant new Grass

Seed by broadcasting over the bare spots depending on whether the overfertilization only affected a section of the lawn or the entire turf. 

The recommended application rate for grass seed is 15-20 seeds per square inch. Spreading 0.25 inches of compost over the area after broadcasting helps boost the  grass seeds’ germination

Note: It’s better to re-sod than to reseed if excess fertilizer killed large areas of the lawn or the entire turf. Unlike reseeding, you don’t have to extensively prep the turf for re-sodding. Even better, you also get a green lawn immediately after installing the new grass-sod pieces.

Undertake Post-Planting Care and Maintenance

After reseeding and fertilizing with compost, irrigate the turf to a depth of six inches. After seeding, deep watering is needed to help with seed germination and root establishment of the soon-to-be grass seedlings.

You should water once daily until germination occurs. However, it’s advisable to irrigate twice per day in high heat conditions with temperatures exceeding 85-degrees Fahrenheit.

You should also fertilize the new turf with a 5-10-5 NPK fertilizer 2-3 weeks post-germination. However, don’t exceed an application rate of 2 teaspoons per square foot. The main objective is to avoid overfertilization.

How do you reverse nitrogen burn?

Technically, you can’t reverse nitrogen burn parse. The discolored grass blades can’t turn green again while the dead roots can’t come back to life. However, you can spur new growth by flushing the excess nitrogen fertilizer out of the soil.

Accidental spills can cause nitrogen burn. The best bet to reverse accidental nitrogen burn is to remove the fertilizer before it seeps into the soil. This method works when you overfertilize while the soil is dry. 

Your next option is reseeding or re-sodding the affected areas. New grass seed should only be planted after leaching the excess fertilizer out of the soil.

Why is my grass dying after fertilizing?

If your turf grass starts to die after fertilizing, you may have fertilized it too soon after the last application. The application led to excessive soluble salts in the soil and dried up the grass.

The application frequency for fertilizer is after 6-8 weeks. Shorter application intervals, such as after every two weeks, will likely kill your grass. 

How do you neutralize fertilizer?

The most effective neutralizing strategy starts with removing the fertilizer or the affected soil. Scoop out the soil in the affected area. 

The next step is to water down the area with as much water as the soil can hold. If possible, aerate the soil to provide more air spaces and create pathways for water to drain. 

The water dilutes the fertilizer salts and flushes them out of the grass root zone. Make sure you repeat the watering for a few days until you are sure the soil is free from the excess fertilizer.

Tips to avoid over-fertilizing Lawn

Always follow the fertilizer brand manufacturer’s application recommendations. The application rate is usually given as the amount of nitrogen in pounds per 1,000 square feet. However, if you find it hard to convert the numbers to the size of your lawn, consider using an ‘online fertilizer calculator.’

Opt for granular fertilizer instead of liquid fertilizer. You can easily sweep or scoop granular fertilizer after accidental application. 

Use a slow-release fertilizer instead of quick-release fertilizer, as you’re less likely to overfertilize. Compost is a great alternative. Its lower mineral content greatly reduces the chances of excessive salt buildup.

References

  1. Bill Hanlin, North Carolina State University (NCSU) Cooperative Extension: Too Much Fertilizer Is Not a Good Thing!.
  2. William Knoop, Michigan State University (MSU) Libraries: Why a Fertilizer Burns

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