15-15-15 Fertilizer: Complete Guide
A balanced granular fertilizer with 15% nitrogen, 15% phosphorus, and 15% potassium. 15-15-15 sits between 10-10-10 and 20-20-20 in concentration: 6.7 lbs per 1,000 sq ft delivers 1 pound of each nutrient. Most common in agricultural use for hay fields, pastures, and pre-plant garden applications where all three macronutrients test low. Less widely available at retail garden centers than 10-10-10 but more cost-efficient per pound of nutrient.
Key Facts
What is 15-15-15 Fertilizer Best For?
When Should You Use 15-15-15 Fertilizer?
Use when a soil test shows all three macronutrients are low, for new garden beds without a soil test history, or as a pre-plant broadcast for vegetable gardens at 4-5 lbs per 100 sq ft. Good for pastures and hay fields at 200-300 lbs per acre.
When Should You NOT Use 15-15-15 Fertilizer?
Avoid on established lawns unless a soil test confirms phosphorus and potassium deficiency. Most mature lawns need nitrogen only. Excess phosphorus causes water pollution and is restricted in lawn fertilizers in several states.