How to Select and Use Inorganic Fertilizers

Blue fertiliser in brown bag on green grass

There are times when your lawn needs a fertilizer that can quickly deliver nutrients to the soil and grassroots. In this case, selecting and using inorganic fertilizers would be your best option.

From precise nutrient ratios and formulations to affordability and availability, inorganic fertilizers offer a more practical approach to addressing soil deficiencies. So, if you want your landscape to be healthy and beautiful, you must know how to choose and use the right inorganic fertilizer.

How to select the right inorganic fertilizer

There’s no one-size-fits-all when it comes to fertilizers. If you compare organic vs. inorganic fertilizers, both are winners in their own turf. That’s why you can’t just pick the same one that worked for your neighbor’s garden and assume it would produce the same results for your lawn.

Even plants of the same type may have different requirements. As such, you’ll need a fertilizer that provides specific nutrients. While various environmental factors contribute to this diversity, one particular element lies underneath it all — the soil.

To choose the right synthetic fertilizer for your lawn, follow these steps:

Step 1: Identify which nutrients to prioritize

Fertilizer in soil. The concept of plant care is the need for feeding with various fertilizers. Text N, P, K, Ca, Mg, S, Mn, Cl, B, Fe, Zn
Adobe Stock

The first step in determining what nutrients your lawn needs is to test the soil. You can do this either via a DIY soil testing kit or by sending a sample of your soil to the lab. The results will help you identify the specific nutritional needs of your plants.

There’s no standard format for these reports. Fortunately, what you need to look for is present in all of them. Nitrogen (N), phosphorus (P), and potassium (K) are the three main nutrients you need to check. If they’re all in adequate amounts, you might not even need to apply synthetic fertilizer.

Out of these three macronutrients, nitrogen is the most important one, as it is what lawns and gardens commonly need. For instance, you can blame the lack of nitrogen in the soil for the slow growth rates of trees and shrubs. Although, it’s not necessarily bad unless you’re aiming for dense shrubbery.

Typically, you only need to do soil testing every three years.

Once you’ve familiarized yourself with the report, it’s time to choose the right fertilizer.

Step 2: Match the fertilizer with the soil report

illustration showing the pH levels of soil
Infographic by Juan Rodriguez

There are numerous things to consider when selecting a fertilizer, and Julia Sirchia, program assistant at UF/IFAS Extension, couldn’t have emphasized it better.

According to Sirchia, “Lawn fertilizers would burn garden plants because they contain too much nitrogen and sometimes other chemicals that are meant to control weeds.” For this reason, she recommends doing your research so you can choose the best fertilizer for your plants.

If you did the soil test, you’re already done with part of the research. For most homeowners, the N-P-K ratio is enough to determine what fertilizer to buy. However, you also must consider whether some plants in your lawn have other specific nutritional requirements.

The plant nutrients pyramid in the figure below can give you a quick overview of what plants usually require. All of these elements are crucial for your plant’s health. However, the nutrients at the base are the most essential, gradually tapering to the micronutrients at the top, which are the least necessary.

Infographic showing Plant nutrients pyramid
Infographic by Juan Rodriguez

Note: If you have a soil pH within the range of 6.0 to 7.0, you can rest assured that you have sufficient micronutrients.

Thanks to the standardized labels, picking a fertilizer from store shelves is easy if you know what you’re looking for. The ratio of N-P-K is always shown at the front of the label in large numbers. For instance, a label of 16-4-8 means 16% nitrogen, 4% phosphorus, and 8% potassium.

You’d be lucky if the N-P-K recommendation from your soil test matches the available bags on the market. Most of the time, you’ll have to compensate by buying fertilizers with different ratios to match the recommendation. Lawn care pros are well-versed in this, so most homeowners rely on them for lawn fertilization services.

Step 3: Calculate how much fertilizer to use

nitrogen, phoshporous and potassium fertilizers on the ground
Adobe Stock

Using the same soil test recommendation, you should be able to calculate the amount of fertilizer you’ll need. Keep in mind that this is for N-P-K only since this is what we’re normally concerned with in lawn care. First, you must list down the values for the following variables:

  • Amount of specific nutrient (in lbs.) per 1,000 square feet, as recommended in the soil test
  • Percent of the specific nutrient in the fertilizer you’re using
  • Area to be fertilized in square feet

The formula to use is:

Fertilizer needed = (N amount of nutrient needed in lbs. / 1,000 sq. ft.) * (1 lb. fertilizer / N percent of nutrient in fertilizer) * area to be fertilized in square feet

For instance, let’s say your lawn is around 1,200 square feet. If your soil report suggests applying 3 lbs. of nitrogen per 1,000 square feet and you have a 16-16-16 fertilizer, you’ll need to apply 22.5 lbs. of the 16-16-16 fertilizer.

Since it can be confusing to compute by hand, you can use this calculator to determine how much N-P-K fertilizer you need:

How to use inorganic fertilizer properly

Lawn fertilizer being spread with a manual fertilizer spreader
Shutterstock

The methods of using inorganic fertilizer largely depend on what the manufacturer suggests on the label. In fact, some labels can even help you determine the best time to use the plant food.

To give you a quick overview, here are three of the methods for applying fertilizers:

Banding

As the term suggests, it involves applying fertilizer in a narrow band next to a furrow where you will plant your seedlings. You need to be extra careful with banding, though, because if the growing roots come into contact with the fertilizer, it could kill the plants.

Broadcasting

With this approach, you’ll be spreading the fertilizer evenly over your lawn with the use of specialized tools such as rotary, drop, or spray spreaders. Fertilizer manufacturers usually provide the settings you need to use in applying their product with the use of spreaders.

Foliar

This process is more effective in boosting micronutrients in plants and works well in conjunction with soil fertilizers. If you go with this method, you will apply the fertilizer directly to the leaves. As always, the product label will indicate if you can apply the fertilizer using this method.

Note: Regardless of the method chosen, remember to be responsible when applying fertilizers. Doing so can help lessen the risks of over-fertilization and any negative environmental impact.

When is it better to use synthetic fertilizer?

Fertilizing plants, lawns, trees and flowers. Gardener in gloves holds white fertilizer balls on grass
adragan | Adobe Stock | License

Brown spots, patchy grass, or yellow blades are just some of the signs of deteriorating soil health. In situations like these, you’ll most likely need an inorganic fertilizer.

These chemical fertilizers are like first-aid solutions for your lawn. They act quickly, which is especially effective if you need to save your plants from dying.

It’s like a laser-targeted approach that rapidly provides your plants with specific nutrients. So, if you need more nitrogen in a problematic spot in your lawn, you can use an ammonium sulfate inorganic fertilizer to revitalize that particular area.

While it seems tempting to rely fully on synthetic fertilizers, there are some drawbacks, including leaching into groundwater. Plus, it’s not a good idea to use inorganic fertilizer in late summer if your goal is to maintain a healthy N-P-K ratio for your lawn in the coming season.

Pro tip: A more cohesive approach to using fertilizers is to have a healthy combination of organic and inorganic, utilizing the best qualities of each.

FAQs about inorganic fertilizers

Are inorganic fertilizers dangerous for pets?

No, they’re not entirely unsafe for pets. In fact, any fertilizer can be pet-friendly as long as you keep your pets away from the lawn for a few days after the application. By the time the soil and grasses have fully absorbed the fertilizer, you can rest assured there’s almost no possibility of ingestion.

What are the most commonly used inorganic fertilizers?

The most common synthetic fertilizers used for lawn care are ammonium nitrate, potassium chloride, and ammonium sulfate. Potassium chloride boosts K nutrients, ammonium sulfate adds nitrogen, and ammonium nitrate is best for foliar spraying on turf grasses.

What is the impact of overusing inorganic fertilizers?

Using too much chemical fertilizer can affect organic matter in the soil, change the soil pH level, and kill beneficial organisms like earthworms – resulting in stunted plant growth. It also can increase the likelihood of pest infestations and even affect the environment by contributing to greenhouse gasses.

Make the right choice for your lawn

The most challenging aspect of selecting the right synthetic fertilizer is getting the correct values of nutrients as recommended by soil testing results. Plus, you need to know the correct timing in applying them.

If you don’t want to get overwhelmed with all this information about inorganic fertilizers, hire a lawn care company in your area today. They can take care of every aspect of fertilization – from selection to application.

Main Image Credit: Adobe Stock

Melanie Joseph

After discovering her passion for writing through her beauty blog, Melanie left her engineering job in California, became a writer, and never once looked back. When she isn't writing, she loves dipping in the pool, tending to the garden, or doing simple home improvement projects.