Best Type of Fertilizer for Your Grass

Most lawns look lush when fed slow-release fertilizer with an N-P-K of around 3-1-2. However, the best type of fertilizer for your grass depends on its type, maturity, and existing soil.

For example, quick-release fertilizer benefits new grass, and centipedegrass needs a more plentiful plate of potassium. Our article explores the pros and cons of various fertilizer types and explains how to find the ideal food for your lawn. 

Discover the key to a lush lawn with our expert guide to fertilizers. From understanding N-P-K ratios to choosing between organic and synthetic options, learn how to select the perfect formula for your yard’s specific needs.

What is fertilizer?

Fertilizer is plant food. It amends soil, adding nutrients that the land lacks. Since a healthy diet inspires a lush lawn, fertilization is a critical lawn care component.

I recently spoke with one of America’s top turf experts, Dr. Becky Bowling of the University of Tennessee. Above all else, she urges homeowners to mow, fertilize, and water their lawns properly. 

Before applying lawn food, it’s essential to understand what fertilizer is made of. Bowling stressed the importance of choosing a fertilizer with the right ingredients: N-P-K, micronutrients, and organic matter. Let’s take a closer look at each.

N-P-K

N-P-K refers to the three numbers displayed on fertilizer bags. These numbers indicate the percentage of nitrogen (N), phosphorus (P), and potassium (K) in the fertilizer mix, in that order. This helps you select the right blend for your lawn’s needs.

• Nitrogen is the main ingredient in most lawn fertilizers because it encourages lush, green growth. Lawns that lack N are prone to short stems, thin leaves, and stunted growth. Additionally, an N deficiency can cause the grass to turn faded green or yellow.

• Phosphorus encourages accelerated root growth and grass seed germination. Well-developed roots help the grass take in more food and water. Thus, a lack of P hinders grass’s development and overall health. It can also cause dark green, purplish, or reddish spots.

• Potassium helps the grass recover from stresses, including pests, fungi, and drought. As a result, turf disease, wilted leaves, and excessive weeds often plague K-deficient lawns. Additionally, a lack of K can cause yellowing and stunted growth. 

Referred to as macronutrients, N-P-K is the most essential meal for plants. “Complete fertilizers” contain all three, while “incomplete fertilizers” lack at least one of them.

Read our complete guide: What is N-P-K? A Guide to Understanding Fertilizer Ratios

Micronutrients

Every now and then, lawns need to nosh on magnesium, iron, and other micronutrients. Fortunately, most soil naturally contains enough of these to keep grass healthy. However, sometimes the soil falls short. Then, fertilizers containing these minor minerals curb iron chlorosis and other micro-deficiencies.

Organic Matter

Plant and animal waste are wholesome fertilizer ingredients because organic matter sustains the soil. Specifically, bio-ingredients encourage loose, nutrient-rich earth. As a result, organic matter reduces mineral deficiencies, soil compaction, and winter desiccation. 

Synthetic vs. organic fertilizer

Synthetic fertilizers are more affordable, but organic products are better for the earth. 

What is synthetic fertilizer?

Synthetic fertilizers contain artificial ingredients, including chemically derived nutrients. Sometimes called “chemical fertilizers”, they often contain fewer nutrients than organic compounds.

Although frequently formulated for fast green-up, chemically derived nutrients degrade the soil. Over time, solely relying on synthetics often leaves land barren. However, some fertilizers have a combination of synthetic and organic ingredients.

What is organic fertilizer?

Organic fertilizers only contain natural ingredients derived from plants and animals. Common examples include compost and manure. Additionally, many organic lawn fertilizers contain animal meal from feathers, fish bones, and blood. 

Although organic fertilizers often contain smaller amounts of N-P-K, they tend to include a broader range of micronutrients. While initial green-up may take longer, natural fertilizers are better for the soil’s long-term condition and viability.

Additional benefits include:

• Safer for children and pets
• Better for the environment
• Less likely to cause fertilizer burn

Granular vs. liquid fertilizer

When comparing liquid vs. granular fertilizers, liquid yields faster results, but granular has a longer effective period. Although granular fertilizers are much more common, liquids are gaining ground. 

What is granular fertilizer?

Granular fertilizers are dry pellets applied to lawns with a fertilizer spreader. It’s applied less frequently than liquid and is easier to store. 

However, granules contain more salt than liquids. According to the University of California, too much sodium dehydrates plants and hinders growth. 

What is liquid fertilizer?

Liquid fertilizers are mixed with water and applied with a sprayer. Some require tank mixing, while others come in ready-to-use bottles that connect to a garden hose. Either way, liquids are easier to apply evenly.

Nutritional benefits are often seen sooner with liquid lawn food because grass absorbs the nutrients quicker and more thoroughly. However, the results are short-lived. Since it takes less time to take in all the nutrients, grass needs more frequent feedings. 

Quick-release vs. slow-release fertilizer

Comparing slow-release and quick-quick-release fertilizers is like a race between the tortoise and the hair. Like the hair, quick-release fertilizers work fast but lack endurance. But like the tortoise, slow-release fertilizers slay when slow and steady to win the race.

According to Amanda Folck, an extension educator at the University of Nebraska–Lincoln, the difference is how quickly the nitrogen is released. “Slow-release fertilizers are more expensive and are slow in releasing the needed fertilizer to the area,” she says.

What is quick-release fertilizer?

Quick-release fertilizers include most liquid plant food. They work best used sparingly for special purposes, including:

• Establishing a new lawn
• Reviving a dying lawn
• Speeding up spring green-up

Grass gorges on quick-release fertilizer, swiftly absorbing the nutrients through its roots. This fast feeding is invigorating. However, it doesn’t take long for the nutrients to deplete. As a result, lawns need more frequent fertilization and are more susceptible to fertilizer burn. 

Folck urges homeowners to carefully apply fast-release fertilizers. She warns that over-application has a high risk of burning grass blades.

What is slow-release fertilizer?

Granular and organic fertilizers usually contain slow-release nitrogen. They provide a gradual stream of nutrients, feeding grass for up to 8 weeks. Over time, a well-balanced slow-release diet leads to lusher lawns.

Although it takes longer to see their benefits, in the long run, slow-release fertilizer wins the race. 

Find the right fertilizer formula

Most lawns thrive on a slow-release fertilizer with an N-P-K ratio of around 3-1-2. However, to find the right formula, you must first complete a soil test.

Soil test

Lawns that lack nutrients can’t thrive. However, over-fertilization is more common and just as harmful. “The biggest mistake I see folks make with their lawns is to over-love them, applying too many inputs – particularly water and nutrients,” Bowling says.

A soil test reveals nutrient, pH, and organic matter levels so homeowners can hone in on the right fertilizer and determine their correct N-P-K ratio.

N-P-K ratios

To find the right fertilizer, you must understand N-P-K ratios:

• Reading labels: Each fertilizer package lists the N-P-K, which is the product’s proportion of primary nutrients.

• Comparing ratios: If you’re recommended a particular N-P-K, select a fertilizer with an equivalent proportion of nutrients.

For example, let’s look at a 10-pound bag of 9-3-6 fertilizer:

• How much N-P-K?  9% Nitrogen (N), 3% Phosphorus (P), 6% Potassium (K)

• How many pounds of N?  0.9 pounds of N, because 10 lb. x  9%=0.9 lb.

• Is the ratio equivalent to 3-1-2?  Yes, because when divide each number in 9-3-6 by 3 we get 3-1-2:

• 9 ÷ 3 =3
• 3 ÷ 3 =1
• 6 ÷ 3 =2

Time of year

Foliage favors different flavors depending on the time of year:

• Growing Season: During its growth season, grass has an ample appetite for N-P-K, micronutrients, and organic matter. Most lawns thrive on a nitrogen-rich, slow-release, complete fertilizer. 

• Off-season: Right before the off-season, lawns need less nitrogen and more potassium. 

Specialty Fertilizers

Sometimes the best lawn fertilizer is formulated to meet a specific need.

Starter fertilizer

Formulated for establishing new grass, starter fertilizers typically have an N-P-K ratio of around 3-4-2 or 10-10-10. Most inspire fast, green growth with quick-release nitrogen. They also contain a plentiful portion of phosphorus to ensure extensive roots. 

Winterizer

Typically applied mid- to late-fall, winter fertilizers prepare lawns for off-season stress. They contain less nitrogen and more potassium than regular fertilizers. 

Weed and feed

Containing both fertilizer and herbicide, weed and feed kills weeds while fertilizing turf. However, if overused or misapplied, weed and feed is bad for grass.

All-purpose fertilizer

With an N-P-K of about 10-10-10, they are generic fertilizers meant for a wide variety of plants.

FAQ about lawn fertilizers

When to call a Lawn Care Pro

Grass needs a well-balanced diet to look deep green and lush. However, homeowners often struggle with fertilization. Not only is there a lot to figure out, but there’s also a lot to do. That’s why so many homeowners trust Lawn Love’s network of local lawn fertilization pros. 

We can also help with over 30 other outdoor services, including lawn mowing, aeration, and weed control in your area. Our user-friendly app makes getting lawn care as easy as ordering a pizza. 

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