NPK ratio, lime, granular or liquid fertilizer: understand everything about lawn fertilization and soil chemistry for optimal results.
Table of Contents5 sections
Table of Contents
Understanding the NPK Ratio
The three essential elements for your lawn are nitrogen (N), phosphorus (P), and potassium (K). Each element plays a distinct role:
- Nitrogen (N): Stimulates leaf growth and gives that intense green color
- Phosphorus (P): Promotes root development (essential for new seeds)
- Potassium (K): Strengthens resistance to diseases, cold, and drought
Which NPK Ratio by Season?
Spring
A nitrogen-rich ratio with slow release (e.g., 20-0-5) to stimulate the lawn's awakening.
Summer
Light or no fertilization to avoid stressing the turf during heat.
Fall — The Most Important!
This is the most important fertilization of the year. A fertilizer promoting root development with a bit more potassium will prepare the lawn for winter [3].
Important: Many regions now ban phosphorus (the middle number, "P") in maintenance fertilizers to protect waterways, unless you're seeding new grass.
When to Apply Lime
Lime should only be applied if a soil test confirms that your pH is too acidic (below 6.0). The ideal pH for most lawns is between 6.0 and 7.0.
Warning: Applying lime blindly can make the soil too alkaline, blocking nutrient absorption (chlorosis) [4].
If necessary, lime can be applied in spring or fall. It takes several months for lime to significantly change soil pH.
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Granular or Liquid: Which Fertilizer to Choose?
Both have their place in a maintenance program:
| Criteria | Granular | Liquid |
| Release | Slow, over several weeks | Fast, direct foliar absorption |
| Burn risk | Low | Moderate if poorly dosed |
| Frequency | Less frequent | More frequent |
| Equipment | Simple spreader | Calibrated sprayer |
| Greening | Gradual | Fast (popular among "Lawn Care Nuts") |
The LawnFan Tip
Get your soil tested before fertilizing. A soil test (available at most garden centers or through your local university) will tell you exactly what your lawn needs — and what to avoid.
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*Sources: [3] Purdue University Extension — Fertilizing Established Cool-season Lawns. [4] Ohio State University Extension — Lime and the Home Lawn.*