Interpreting Soil Test Recommendations: 5-10-5 Fertilizer for Tall Fescue Renovation

Why 1:2:1 Ratio?

Your soil test shows phosphorus deficiency. The 5-10-5 (or any 1:2:1 ratio) supplies double the P relative to N and K to correct this.

Finding the Product

• Starter fertilizers (e.g., 21-28-4, 18-24-6) approximate this ratio and are widely available.
• Balanced 10-10-10 works if you double the rate (but you'll over-apply N and K).
• Specialty turf suppliers or farm co-ops often carry 5-10-5, 8-16-8, or 10-20-10.

One Fertilizer for Whole Lawn

Use the starter/high-P fertilizer on both renovated and existing areas. The established grass won't be harmed by extra phosphorus, and the new seed gets the P it needs for root development.

Nitrogen Burn Myth

Modern starter fertilizers (20-27-5, etc.) are safe for seedlings if applied to dry soil and watered in immediately with 1 inch of water. The 10% N max rule is outdated—coated urea and polymer technologies control release.