Reasons To Fertilize Your Lawn

To live, plants must carry on photosynthesis, a process that requires sunlight, oxygen, water, and nutrients. Sunlight and oxygen are taken from the atmosphere, while water and nutrients are absorbed through the roots and transferred to the leaves to support photosynthesis.

Without all of the building blocks they need, grass will struggle to become the lush green lawn most homeowners want. Well-fed plants grow healthier and more beautifully, but they are also more productive and more resistant to poor weather conditions and disease.

As nutrients in the soil are used up by growing grass, they are not naturally replenished in an urban ecosystem. They need to be added back into the soil.

Fertilizers supplement the nitrogen, phosphorus, and potassium that grass needs in large amounts to grow healthy and strong. Grass growing in unfertilized soil is often deficient in nutrients, which can result in slower growth and a weaker appearance.

Fertilizer Basics

N-P-K

To understand the nutrients in lawn fertilizer, look at the three numbers separated by dashes on the package. These represent the primary plant nutrients:

(N) Nitrogen – (P) Phosphorus – (K) Potassium

These are usually the first nutrients to become lacking in the soil and the ones plants need most. They are called macronutrients because plants use them in large amounts for growth, survival, and photosynthesis. These nutrients can also leach from the soil naturally due to weather, especially during rainy seasons or prolonged hot weather.

Nitrogen (N)

Nitrogen is what helps grass look green. It is a key component of chlorophyll and is crucial for photosynthesis. Without enough nitrogen, plant growth becomes stunted and the leaves begin to yellow.

A visible sign of nitrogen deficiency is when the grass loses its rich emerald-green color and turns a lighter yellow-green shade, often with a slower growth rate.

More nitrogen = more foliage, which is exactly what a lush green lawn needs.

Phosphorus (P)

Phosphorus is required for plant growth and is found in every living plant cell. It promotes root growth and helps develop deep, strong root systems that are better able to resist dry conditions.

If phosphorus is lacking, grass may have weak roots that cannot efficiently reach water and nutrients in the soil.

Potassium (K)

The symbol K comes from the Latin name for the element, kalium. Potassium helps make grass more resilient by improving its ability to withstand extreme cold, drought, and disease.

Potassium also helps regulate how the plant uses available nitrogen, supporting the greenness of the lawn through the photosynthetic process.

Grass needs potassium throughout the growing season, but it is especially valuable in the fall. Fall fertilizer blends often contain higher levels of potassium and are commonly labeled as winterizers.

Higher potassium levels improve the lawn’s ability to tolerate environmental stress, including cold damage. These fertilizers help the grass absorb and retain nutrients, strengthen cell walls, and fortify root systems before winter arrives.

Other Essential Nutrients

It is important to note that carbon (C), hydrogen (H), and oxygen (O) are also crucial elements for plant survival, but plants usually get these in abundance from the air and water.

There are also three additional essential nutrients that plants require in smaller amounts. These are called secondary nutrients:

• Calcium (Ca) – Helps bind organic and inorganic particles, improves soil structure, and is important in the growth and development of plant cell walls.
• Magnesium (Mg) – Contributes to the green coloring of plants and is found in chlorophyll, helping plants process sunlight.
• Sulphur (S) – Supports the production of proteins, amino acids, enzymes, and vitamins, and is important for growth and seed formation.

Elements needed in very small amounts are called micronutrients, also known as trace elements. These include:

zinc (Zn), boron (B), manganese (Mn), iron (Fe), molybdenum (Mo), chlorine (Cl), and copper (Cu).

N-P-K Ratio

The ratio of macronutrients in fertilizer varies depending on the season, the type of plant being fertilized, and the growth goals. However, the order on the label is always N-P-K.

Understanding the Numbers

Because fertilizers are mixed with inert materials, their strength is measured as a percentage of total weight.

For example, a fertilizer labeled 20-10-15 contains:

• 20% nitrogen
• 10% phosphorus
• 15% potassium

The remaining percentage is made up of micronutrients and inert materials. These percentages are given in the standard fertilizer forms of N, P2O5, and K2O.

Application Rate

More does not equal better when it comes to fertilizer.

Applying too much fertilizer at once can damage your lawn. High concentrations of nutrients can be too strong for the grass, resulting in fertilizer burn and other stress.

For best results, schedule fertilizer applications once every 6 to 8 weeks starting in the spring, depending on your lawn’s needs and how much maintenance time you can commit to. Too little fertilizer may not support healthy growth, while too much can harm the lawn.

Knowing how much fertilizer to use means understanding the application rate. This rate is generally based on the amount of nitrogen (N), measured in pounds, recommended per 1,000 square feet of lawn.

Because fertilizer formulas vary in their nitrogen concentration, different products will require different application rates. It often takes a few applications to learn what works best for your particular lawn, and that is normal.

Most cool-season grasses require about 2 to 6 pounds of nitrogen per 1,000 square feet each year for optimal health. Fescue grasses generally need less nitrogen than bluegrass.

For best results, divide the total yearly nitrogen amount into several applications throughout the year. A commonly suggested rate is 1 pound of nitrogen per 1,000 square feet per application, but always read the product label and adjust based on your lawn’s response.

Schedule of Fertilizer Application

For cool-season grasses, the best approach is to fertilize lightly in the spring and more heavily in the fall. If you only fertilize once a year, the most beneficial time is usually late summer or fall, ideally after the last mow of the year.

Fertilizing every 6 to 8 weeks can produce the healthiest and greenest grass. A properly fertilized lawn will be better able to withstand extreme weather, recover more quickly from foot traffic, and resist disease more effectively.

Following a 6-to-8-week schedule usually results in approximately 5 fertilizer applications per year.