Best fertilizer to thicken grass

There's this one baseball field where we go to practice sometimes. It never has thick grass. It always has large sections that have little to no grass. Other fields in the same park have nice, thick grass.

So, why does one field have thick grass and what is the best fertilizer to obtain thick grass?

Before we can answer the question about the best fertilizer to thicken grass, we have to look at what causes grass to be thin and what is the overall process to thicken grass. Applying any fertilizer without understanding what is making your grass thin in the first place, will not help you to make it thick and keep it thick.

What's causing your lawn to be thin

There are several factors that will cause your lawn to be thin. Fertilizer can be one of the causes of your lawn being thin.

Too much fertilizer

Too much fertilizer, in particular, too much nitrogen can cause your grass to thin. Many fertilizers that are meant to thicken your grass contain nitrogen. The nitrogen can be good to thicken your grass, but you first need to know how much nitrogen is in your soil. You can test your nitrogen levels with a soil test kit.

Fertilizers use minerals to provide nitrogen to your soil. When there is an excess of the minerals, salts begin to build up. The salt build up absorbs moisture and prevents your grass roots from absorbing some of the water.

Dry soil

Grass needs water to grow. If your grass is not getting enough water it will grow slow, become dormant, or die. Dry, hard soil can make it difficult for your plants to absorb water, even when you provide water.

When your soil is too dry, it can repel water. One way to improve the moisture of your soil is to aerate it by poking holes in your lawn. You can get an aerator tool and roll it over your lawn. Then water your lawn regularly. You will want to aerate the lawn often until the soil starts to absorb water well.

Soil pH

A balanced pH is key to having your grass grow thick. If your soil is too alkaline, your grass won't be able to absorb enough water. If your soil is too acidic, dangerous minerals, such as aluminum, will break down in the soil. These minerals will harm your grass and cause it to thin.

Each type of grass has its own preferred pH range. Learn what is the preferred pH range for your grass. You can test the pH levels with a soil testing kit.

Not enough sun

Grass needs sunlight to grow. If your grass is not receiving enough sunlight it will hesitate to grow. To improve sunlight on your lawn, cut back trees and shrubs that are blocking the sunlight from reaching your lawn.

You can also use reflective materials to add light to your shaded spots. This is often used in greenhouses and under trees in groves to help radiate solar energy to the plants and trees.


Fungus can sometimes cause brown spots in your lawn. Fungus lives below the grass during the winter and attacks the lawn when it is warmer. Fungus causes the blades of grass to become brown.

Proper lawn care will help to eliminate fungus from your lawn.


Some bugs and worms like to eat grass. When your lawn is in a poor state of health, it can be even more attractive to these pest. Grubs, chinch bugs, armyworms, and other pest will eat grass at the thatch layer, causing your lawn to thin and turn brown.

Check the thatch layer of your grass to see if you are being invaded by any of these pest. Take steps to remove them from your lawn before trying to thicken it.

What fertilizer can and cannot do to thicken grass

Fertilizer is needed for your grass to thicken, but fertilizer can't do the whole job. Fertilizer adds nutrients to your lawn that will help it to grow. Some fertilizers have more of certain nutrients than others. Some fertilizers are fast release and others are slow release. These factors, along with the present health of your lawn, will affect how thick your grass will grow.

Nitrogen is the main ingredient in fertilizers that can effect how thick your grass grows. A fertilizer's nutrient content is represented by a three number tagging system known as its N-P-K number. The first number in the tag is for the amount of nitrogen present in the fertilizer. So, if you see a fertilizer with the numbers 30-10-10 on it, there is 30% nitrogen in the fertilizer.

Extra nitrogen will help your lawn become thicker. Nitrogen will help your existing grass to thicken. If you have empty spots in your lawn or if your existing grass doesn't get thick enough, you will need grass seeds to make your lawn thicker.

Preparing your lawn for seeding

To prepare your existing lawn for seeding, also called overseeding, you should use an aerator or rake to loosen the soil and grass. This will give the new seeds you spread a place to fall into the soil and germinate.

Also, if you have dead grass, you should remove it before spreading your seeds.

Overseeding to thicken grass

Overseeding is the process of spreading new seeds onto your existing lawn to create new sprouts. Overseeding is used to fill in bare spots and to thicken your lawn.

When overseeding, first aerate your lawn so it is ready to receive the new seeds. Spread the seeds out by broadcasting them. You can broadcast the seeds by hand or with a lawn spreader. If you are spreading your seeds by hand, be sure to spread them evenly.

You should water your new seeds regularly. Also, provide your new seeds the nutrients they need by giving them a fertilizer that is high in phosphorus.

Other steps you can take to thicken your grass

There are a few other things you can do to thicken your grass. Mulch your grass when you cut it. Mulching adds seeds from the cut grass back into your lawn. It also provides nutrients back into the soil.

Another thing you can do is to collect your grass clippings in a bag. Then spread them in the areas that need thickening. This way you can control where you want the seeds from the clippings to germinate.


Fertilizer is a good way to make your grass thicker. The best fertilizer to make your grass thicken is the one that works with your grass and soil type. Test your soil to make sure it is in a good range for nitrogen and pH levels before adding fertilizer to your lawn to thicken it. Be sure to water your lawn regularly and use overseeding to put seeds in the areas where there is little to no grass.