A Beginner’s Guide to Granular Fertilizers

Maintaining a lush, healthy lawn involves more than just regular mowing and watering. One crucial aspect of lawn care is fertilization, and understanding the different types of fertilizers available can help you make informed decisions for your yard. This beginner’s guide will introduce you to granular fertilizers, explain the importance of NPK ratios, and discuss slow-release versus quick-release nitrogen sources. We’ll also touch on the significance of soil fertility testing and your fertilizer’s physical properties.

Understanding NPK

When you pick up a bag of fertilizer, you'll notice three numbers prominently displayed on the front, such as 10-10-10 or 20-5-10. These numbers represent the NPK ratio, which stands for Nitrogen (N), Phosphorus (P), and Potassium (K). These three elements are referred to as primary macronutrients, as they are found in the highest quantities within the plant.

For example, a bag labeled 20-5-10 contains 20% nitrogen, 5% phosphorus, and 10% potassium. The remaining percentage consists of filler materials that help distribute the nutrients evenly.

• Nitrogen (N): Essential for promoting top growth and plant vigor.

• Phosphorus (P): Crucial for root development and flowering.

• Potassium (K): Helps with disease resistance, drought tolerance, and overall hardiness.

A simple saying that helps me remember this is "Up, Down, All around." Nitrogen (N) promotes top growth and turfgrass vigor ("Up"), Phosphorus (P) plays a crucial role in root function and development ("Down"), and Potassium (K) is involved in most processes within the plant, particularly hardiness ("All around").

Interestingly enough, if you've ever seen a bag of fertilizer recommended as a "starter fertilizer" or used for establishing seed or sod, you might have noticed that the middle number on the bag is quite high. Promoting root growth and function is important when establishing seed and sod, so this makes sense.

Slow-Release vs. Quick-Release Nitrogen

Slow-Release Nitrogen

Slow-release fertilizers release nitrogen gradually over time, providing a steady supply of nutrients. This reduces the risk of burning your lawn and decreases the frequency of applications. Here are some common slow-release nitrogen sources which you should be able to identify on the product label:

• Polymer-coated urea: Tiny urea granules coated with a polymer that controls the release rate. These coatings break down slowly, typically through water, temperature, and microbial activity.

• Sulfur-coated urea: Urea granules coated with sulfur, which breaks down slowly to release nitrogen.

• Methylene urea: A synthetic nitrogen source that breaks down through microbial activity, providing a slow, steady release of nitrogen.

• Urea-formaldehyde: Another synthetic slow-release nitrogen that decomposes slowly under microbial action.

• Natural organic fertilizers: Products such as composted manure or bone meal release nitrogen slowly as they decompose, feeding your lawn over a longer period.

When discussing fertilizers with a product specialist or professional land manager, you might hear the term "Controlled Release" or "CRN." Depending on who you ask, some might classify all the listed sources above as CRN, while others might refer to CRN as only the polymer-coated products. By definition, all slow-release products are "Controlled Release" because the rate at which they release nutrients into the soil is "controlled" by environmental factors like heat, microbiology, water, etc. However, there has been a great deal of research put into controlling the release of nitrogen in a professional setting with polymer-coated products. In some regions, you can conduct a test to determine, to the week, how long you can expect the product to be releasing nutrients for. For homeowners, this level of detail might not be necessary, but it’s a good habit to ask what the nitrogen source is when being sold a "slow-release" or "CRN" fertilizer, as it could affect your decision and explain price differences.

Quick-Release Nitrogen

Quick-release fertilizers provide an immediate supply of nitrogen, which can be beneficial for rapid greening or recovery from stress. However, they carry a higher risk of burning your lawn if not applied correctly. Here are some common quick-release nitrogen sources:

• Urea: A highly soluble nitrogen source that dissolves quickly in water, providing an immediate nitrogen boost. This is often used when a fast green-up is desired.

• Ammonium nitrate: A fast-acting nitrogen source that provides quick results. However, it's highly soluble and can leach away quickly, especially in sandy soils.

• Ammonium sulfate: Another quick-release option that lowers soil pH while providing a rapid nitrogen boost. This is beneficial for lawns that need both immediate greening and slight acidification.

• Calcium nitrate: Provides both nitrogen and calcium, offering a quick green-up and serving as a liming agent.

The Importance of Soil Fertility Testing

Before selecting a fertilizer, it's essential to conduct a soil fertility test. This test identifies nutrient deficiencies and helps you choose the right product for your lawn. A soil test can save you money by preventing over-application of fertilizers and ensuring your lawn receives the nutrients it truly needs.

If you need help interpreting the results of your soil test, don’t hesitate to reach out to us. We're here to assist you in making the best choices for your turf.

Particle Size (SNG)

The size of the fertilizer particles, or SNG (size guide number), affects the distribution and application of the product. Smaller particles provide more even coverage but can be more challenging to spread evenly. Larger particles are easier to spread but may result in less uniform coverage. Choose a product with a particle size that matches your spreading equipment and desired application precision. Generally, you'll find products on the market with an SNG of 80 - 250+. If cutting at over an inch, you’re probably going to be fine with a 250 SNG. However, if you're getting technical with your lawn care program and using a reel mower to achieve lower heights where better coverage may be important, consider investing in a smaller SNG product.

Homogenous vs. Blended Products

Homogenous Fertilizers

Homogenous fertilizers contain all the nutrients listed on the label in each granule. This ensures that every part of your lawn receives the same nutrient mix, promoting even growth and reducing the risk of nutrient imbalances.

Blended Fertilizers

Blended fertilizers consist of individual granules of different nutrients mixed together in the same bag. While often more cost-effective, there's a risk that the nutrients may not be evenly distributed, leading to uneven growth and potential nutrient deficiencies.

Selecting a Product for Your Property

As this is a basic guide to granular products, we will not dive deep into the process of selecting a product right for your landscape. However, it may be helpful to recap what we've covered so far if your eager to get into the market:

• The three numbers on the front of a bag of fertilizer represent the N-P-K ratio.

• Generally, there are two overarching types of nitrogen sources: slow-release and quick-release, both having pros and cons with specific use cases.

• Soil testing is imperative before applying products. Let's stay educated and environmentally conscious. It’s hard to build a house without a foundation. A soil test is your foundation.

  • Any questions regarding fertility results from a soil test can be directed to us. We will do our best to help.

• The physical product itself can be described using an SNG (size of the prill) and whether the product is blended or homogeneous.

As we dive further into the world of fertilizers and how to select the right ones, you’ll notice some common themes. The NPK on the front of the bag is not the only factor determining its price. Generally, the high-quality slow-release, low SNG, homogeneous products will be the most expensive, as they are the hardest to make and the most desired by professional managers.

Conclusion

Understanding the basics of granular fertilizers can help you make informed decisions for your agronomic program. By considering the NPK ratio, nitrogen release type, and physical properties of the product, you can tailor your fertilization strategy to meet your lawn's specific needs. Remember, a soil fertility test is a crucial first step in this process, and we’re here to help you interpret those results and choose the best products for your lawn.

Stay tuned for a detailed guide on deciding what products are best for your property.

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