Do You Need Starter Fertilizer When Seeding a New Lawn?

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Are you planning to seed a new lawn and wondering if you need to use a starter fertilizer? This is a common question among homeowners and landscapers. In a recent study, soil starter fertilizer was put to the test in a controlled experiment, providing valuable insights for anyone establishing new turf.

What Is Starter Fertilizer?

Starter fertilizer is a blend that contains nitrogen (N), phosphorus (P), and potassium (K)-the three key nutrients for plant growth. Unlike many standard lawn fertilizers that may lack phosphorus, starter fertilizers typically have a higher phosphorus content. For example, the study compared a 24-25-4 starter fertilizer (high in phosphorus) with a 32-0-4 standard lawn fertilizer (no phosphorus).

The Experiment: Sand vs. Native Soil

The trial used two different soils:

Washed Sand: Virtually devoid of nutrients.
Native Silt Loam Soil: Contained adequate nitrogen, phosphorus, and potassium based on a pre-plant MySoil soil test.

Both soils were seeded with an 80/20 Perennial Ryegrass /Kentucky Bluegrass mix and either treated with no fertilizer (control), starter fertilizer, or standard fertilizer. The results were telling:

In Washed Sand: The starter fertilizer produced the best turf color, density, and vigor. The standard fertilizer improved growth compared to the control, but not as much as the starter fertilizer.
In Native Soil: Both starter and standard fertilizers improved turf compared to the control, but there was little difference between the two fertilizer types. Since the native soil already had sufficient phosphorus, the extra phosphorus in the starter fertilizer didn’t provide additional benefit.

Key Takeaways: When Is Starter Fertilizer Necessary?

Low-Phosphorus or Low-Nutrient Soils:
If your soil is low in phosphorus or generally nutrient poor (like sand), a starter fertilizer with phosphorus is highly recommended. It will significantly boost seedling vigor, color, and density.
Soils with Adequate Nutrients:
If a soil test shows your soil already has adequate phosphorus, a starter fertilizer is less critical. Standard lawn fertilizer or a slow-release nitrogen product may be sufficient.
If You Haven’t Tested Your Soil:
If you haven’t used a soil test kit (like MySoil) and don’t know your nutrient status, using a starter fertilizer is a safe bet to ensure your new lawn gets the phosphorus it may need for strong root development.

Practical Tips for Lawn Seeding Fertilization

Soil Stratification: In real lawns, nutrient levels can vary with depth. If you have good nutrient levels at the surface but not deeper, roots may struggle as they grow. Alternatively, early growth may be stunted without starter fertilizer until the roots grow into a depth with more available nutrients, such as phosphorus. Starter fertilizer can help bridge this gap either way.
Timing: If your soil is fertile, consider delaying fertilizer for up to three weeks after seeding, or use a slow-release nitrogen product to avoid excessive early growth before roots are established.
Always Test First: The best way to know what your lawn needs is to use a soil test kit. MySoil Soil Test Kits provide fast, accurate results and tailored fertilizer recommendations.

Conclusion

Starter fertilizer is most beneficial when seeding into soils that are low in phosphorus or overall nutrients. In soils with adequate fertility, it may not provide significant additional benefits. When in doubt, test your soil first-this ensures you apply the right product at the right rate for the healthiest, most vigorous new lawn.

Ready to seed your lawn?
Order a MySoil Soil Test Kit to get started with confidence and grow your best lawn yet!

Keywords: starter fertilizer, lawn seeding, soil test, phosphorus, new lawn, MySoil Soil Test Kit, turf establishment, lawn fertilizer, soil nutrients, SoiLab