How to Fertilize Lawn – Always Have the Best Lawn

Just as a person needs minerals and vitamins to live, the natural lawn also needs nutrients for its development. That is why in this article we will explain everything about how to fertilize lawn correctly.

Plants do not need complex compounds, such as vitamins or amino acids, essential in human nutrition, because they synthesize all those they need. They only require a dozen chemical elements, which must be in a form that the plant can absorb.

Among the necessary nutrients, air and water provide hydrogen, oxygen, and carbon in inexhaustible quantities. Almost all soils contain an abundance of sulfur, calcium, iron, and other essential nutrients.

Calcium is often added to the soil, but its primary function is to reduce acidity, not to act as a fertilizer in the strict sense. Nitrogen is present in the atmosphere in enormous quantities, but plants cannot use it in this way; certain bacteria provide plants with the necessary nitrogen, which they take from the air and transform it through a series of reactions called “nitrogen fixation”.

The three elements that almost all fertilizers must contain are nitrogen, phosphorus, and potassium. Occasionally, small amounts of some others, including boron, copper, and manganese, must be added to these.

For a green, lush, healthy, weed-free natural lawn, you will need to know the nutritional needs of your lawn and apply for the correct fertilization program. To do this you will need to determine what variety of grass you have, what properties the soil has, and when and how you should apply fertilizer.

Why Is It Necessary to Fertilize Lawn?

Not all soils provide the necessary nutrients to the lawn and those that do, with time the nutrient reserves are diminishing. The natural lawn is a great consumer of energy and very sensitive to the lack of nutrients. Fertilizers are a fundamental part of the development of the lawn together with good irrigation and proper mowing. The reasons why it is necessary to fertilize the lawn are:

– There are very sandy soils, with very few nutrients and that lose them by the passage of water (washing).

– The continuous mowing to which the lawn is subjected, makes necessary a correct supply of nutrients to help it recover.

– It helps it to recover from trampling and damage caused by diseases, insects, and fungi. It strengthens and prevents them from attack.

– Stimulates leaf and root growth.

– Replenishes nutrient losses caused by filtration, volatilization, removal of grass clippings, and by the lawn’s consumption.

– Helps to reduce and control weeds.

– A lawn with low nitrogen content develops chlorosis (yellowing) and achieves low plant mass and low density.

why is it necessary to fertilize lawn

Steps Before Fertilizing Lawns

To find out how much and how much fertilizer your lawn needs, follow these recommendations:

  • Test the soil.
  • You must know the pH of the soil. Depending on whether it is very high (alkaline) or low (acidic), you will need one fertilizer or another. Ideally, it should be at 6.5 or between 5.5 / 8 pH. We use this soil pH meter (Order it here).
  • Identify the lawn variety.
  • Some fertilizers are marketed for certain varieties of lawns, although this is not the norm.
  • Calculate the lawn area.

Types of Lawn Fertilizers

Based on their form or state of presentation, they can be classified as follows:

Fertilize Lawn: Liquid Fertilizers

They are fast-acting. Penetrate the soil and quickly reach the roots. They are usually mixed with water, using applicators that are attached to the hose or automatic irrigation system. Because it is absorbed so quickly, it is necessary to apply it every 2 / 3 weeks.

Fertilize Lawn: Granular Fertilizers

They are applied broadcast or with a spreader for large surfaces. They need to be watered for their dissolution and penetration into the soil. Their application is easy to control since we know at all times when and how much fertilizer each zone receives.

Granular fertilizers can be slow-release or fast release:

Slow-Release Granular Lawn Fertilizer:

Releases nutrients little by little, gradually according to the needs of the plant. Thus, there is less loss of nutrients by washing and evaporation. Some act for ± 8 weeks (they are coated by a sulfur layer) and others act for ± 12 weeks (they are coated by a polymer layer).


– Nourishes properly over a long period, adapting to the needs of the lawn.

– Avoids excessive growth of the lawn, since the element that causes it, Nitrogen (N), is released slowly.

– Reduced loss of nutrients through water (leaching) and evaporation.

– Reduced risk of burns.

Fast Release Granular Lawn Fertilizer:

Releases nutrients in ± 4 weeks.

All of the above times vary depending on the receiving water and temperature.

Some fertilizers combine an herbicidal action while nourishing. They are of two types:


It is applied in early spring before the weeds emerge since once they germinate the herbicide does not affect them.


It is a contact fertilizer herbicide and is only effective against weeds that have started to grow, not against weeds that have not yet germinated.

types of lawn fertilizer

Symbology To Understand Fertilizer Composition

Fertilizers are a compound of different chemical elements and proportions. Once the needs of the lawn in terms of nutrients have been determined, it is necessary to choose the appropriate fertilizer.

If you are not familiar with the chemical terminology of fertilizers, here are the keys to understand what they contain.

The chemical elements are represented by one or two letters to simplify their inscription. The 3 most important not only for lawns but for any plant are Nitrogen, Phosphorus, and Potassium.

– Nitrogen – N: It favors the development of the leaves and provides the bright green color and is the most abundant element in the plant, it constitutes ± 4 % of the plant.

– Phosphorus – P: Helps root development.

– Potassium – K: Helps root development and provides resistance to diseases, drought, and intense cold.

– Calcium – Ca: For root development.

– Magnesium – Mg: For the formation of sugars, an essential component of plant tissue.

– Sulfur – S: To enhance greenness. Mixed with lime, it has a fungicidal action.

– Zinc – Zn: It participates as an enzymatic cofactor in many metabolic processes of plants, including the creation of the vital hormone for the growth and development of the lawn. It is also essential for nitrogen metabolism and protein synthesis.

– Iron – Fe: Fundamental element for growth, since it is a component of chlorophyll and proteins. It is one of the micronutrients that are needed in greater quantities. Its deficiency is denoted in yellowish lawns.

– Manganese – Mn: Together with iron, it improves photosynthesis.

– Copper – Cu

– Molybdenum – Mo

Interpretation Of the Fertilizer Formula

In many bags, sacks and cans we will find a formula similar to this one: 20 – 10 – 5.

This formula means that the composition of the fertilizer has the following elements:

20 % Nitrogen.

10 % of Phosphorus.

5 % of Potassium.

The first figure will always correspond to Nitrogen, the second figure will always correspond to Phosphorus and the third figure will always correspond to Potassium.

Which Lawn Fertilizer to Use?

It depends on the type of lawn, soil, the season, climate, what the lawn is used for. Here are some examples:

Ornamental lawns, with fine species such as Agrostis.

1.7 oz (50 gr). per 10 ft² (m²) of 15-15-15 in mid-spring and early fall and 1 oz (30 gr). in mid-summer.

broadcasting machine

Adequate Amount of Fertilization

It depends on the composition of the fertilizer and the way it acts (slow or fast release of nutrients). Always follow the manufacturer’s instructions.

These are the following lawn fertilizers that we recommend:

Scotts Turf Builder Lawn Food - Fertilizer for All Grass Types, 5,000 sq. ft., 12.5 lbs.
Scotts Turf Builder Lawn Food - Fertilizer for All Grass Types, 5,000 sq. ft., 12.5 lbs.
Apply lawn care product to a wet or dry lawn; Grass fertilizer works on any grass type; One 12.5 lb. bag of Scotts Turf Builder Lawn Food covers 5,000 sq. ft.
$16.50 Amazon Prime
Scotts Turf Builder Weed and Feed 3; Covers up to 5,000 Sq. Ft., Fertilizer, 14.29 lbs.
Scotts Turf Builder Weed and Feed 3; Covers up to 5,000 Sq. Ft., Fertilizer, 14.29 lbs.
One 14.29 lb. bag of Scotts Turf Builder Weed and Feed3 covers 5,000 sq. ft.; Not available in FL
$23.87 Amazon Prime
Scotts Green Max Lawn Food, 16.67 lbs.
Scotts Green Max Lawn Food, 16.67 lbs.
Feeds for deep greening in just 3 days; Dual-action, 2-in-1 formula feeds and supplements with iron
$33.20 Amazon Prime
Scotts Turf Builder Triple Action - Weed Killer & Preventer, Lawn Fertilizer, Prevents Crabgrass, Kills Dandelion, Clover, Chickweed & More, Covers up to 4,000 sq. ft., 20 lb.
Scotts Turf Builder Triple Action - Weed Killer & Preventer, Lawn Fertilizer, Prevents Crabgrass, Kills Dandelion, Clover, Chickweed & More, Covers up to 4,000 sq. ft., 20 lb.
Triple Action kills, prevents and feeds; Prevents crabgrass for 4 months and feeds to build thick green lawns
$34.97 Amazon Prime

We can say that in general, a natural lawn needs about 2.6 lbs (1.2 kg) of nitrogen per 1076.39 ft² (100 m²) per year, distributed 3 times a year. This means that of a fertilizer with a composition, for example, of 20-4-10, and knowing that figure 20 means 20% of Nitrogen per 220 lbs (100 kg) of fertilizer, we will have to apply a total of 13 lbs (6 kg) of this fertilizer per year to provide the recommended 2.6 lbs (1.2 kg) of Nitrogen. A simple rule of three is enough to know the amount of fertilizer to use.

When to Fertilize Lawn – Frequency of Fertilization

Fertilize when the natural lawn is in its growing season. Fertilizing during dormant periods such as cold or hot weather will not make the lawn grow more.

Cool Season Lawns

Fall: Fertilize generously when the heat has subsided.

Spring: Fertilize very lightly early in the season, either with a slow or fast release fertilizer, but have it take effect before the arrival of high heat.

Warm-Season Lawns

Spring: Fertilize when greening begins, either with a fast or slow-release fertilizer, but make sure it takes effect before summer. With the arrival of intense heat, stop fertilizing.

Autumn: Fertilize when the intense heat has subsided.

These are general recommendations. Follow the specific instructions of each fertilizer. Too little fertilizer will have little effect on the lawn, and too much will burn the lawn. Also, do not fertilize in intense heat or cold as this can damage the lawn.

Slow-release fertilizers can be used twice a year, once at the end of summer, when the excessive heat subsides, approximately at the beginning of September (depending on the area), and once at the end of winter when the cold subsides, approximately at the beginning of March.

How to Fertilize Lawn

In general, it is necessary to avoid concentrations of fertilizer when applying it so that the lawn does not burn. The normal method is manually (broadcasting), but if the lawn is very large you can acquire a tool to facilitate the task. It is also necessary to water abundantly once the fertilizer has been applied so that it dissolves and penetrates the soil and does not burn the plant.

It is advisable to fertilize one day after mowing.

Here are some tools that will help you fertilize your lawn more easily.

Scotts Wizz Spreader - Handheld Power Spreader, Use Year-Round, Covers Up to 2,500 sq. ft., Brown
Scotts Wizz Spreader - Handheld Power Spreader, Use Year-Round, Covers Up to 2,500 sq. ft., Brown
Designed to cover up to 2, 500 sq. ft. using Scotts lawn care product; 5-foot broadcast with control of EdgeGuard Technology
$25.96 Amazon Prime
Scotts Turf Builder EdgeGuard Mini Broadcast Spreader - Holds Up to 5,000 sq. ft. of Lawn Product, Green
Scotts Turf Builder EdgeGuard Mini Broadcast Spreader - Holds Up to 5,000 sq. ft. of Lawn Product, Green
Comes pre-calibrated and fully assembled with a fold-down handle for easy storage
$47.97 Amazon Prime
Agri-Fab 85-Pound Push Broadcast Spreader 45-0388 , Black
Agri-Fab 85-Pound Push Broadcast Spreader 45-0388 , Black
Towed on 2 10-by-1-3/4-inch pneumatic treadcap wheels; Assembled Product Size: 35" x 22" x 33"
Agri-Fab 45-0462 Push Broadcast Spreader,Orange & Black,130-lb Capacity
Agri-Fab 45-0462 Push Broadcast Spreader,Orange & Black,130-lb Capacity
45-0614 has now replaced 45-0463; HOPPER CAPACITY: 130 lbs.; 1/2 acre (25,000 sq. ft.); SPREAD WIDTH: 10- 12 ft. spread

Fertilizer should not be applied when the lawn is wet or damp as it will stick to the blades and burn them.

how to fertilize lawn

Granular Fertilizer:

Both the applicator and the fertilizer must be dry.

Whether you use an applicator or broadcast, to make the fertilizer distribution as uniform as possible, divide the amount to be applied in two halves and spread it in two passes in a criss-cross manner, i.e., one pass horizontally and one vertically.

Clean the spreader thoroughly after use.

Liquid Fertilizer:

Move the jet of the applicator with lateral passes, slowly and with a constant rhythm.

Clean the applicator well after use.

We hope this complete guide on how to fertilize your lawn will be very useful and that you will have the best lawn in your garden.

About Henry Morgan

We are the Morgans, Henry, and Julia, both agronomists from the University of Michigan, where we met. We are experts in putting our hands in the soil and developing organic foods and improving production processes for decades. Likewise, we have worked for companies such as Mondelez International, BASF, Monsanto, etc. currently in our role as science writers for as well as advisors in promoting large scale food growing in urbanized areas. In this website, we share what we are most passionate about, gardening and farming. Enjoy and see real photos on our website.