15-15-15 vs 20-20-20 Fertilizer: Granular vs Water-Soluble

Colorado State University Extension: Fertilizing the Vegetable GardenWikipedia: NPK Rating
Verdict

15-15-15 is the go-to for outdoor gardens, lawns, and large areas because it is granular and easy to spread. 20-20-20 is best for container plants, hydroponics, and foliar feeding because it dissolves completely in water.

How Do 15-15-15 Fertilizer and 20-20-20 Fertilizer Compare?

15-15-15 Fertilizer wins 3 of 5 categories. The breakdown below covers application method, nutrient concentration, container growing, large area coverage, cost per acre.

Factor15-15-15 Fertilizer20-20-20 Fertilizer
Application Method
15-15-15 granular is broadcast with a spreader, fast and simple. 20-20-20 requires mixing with water
8
7
Nutrient Concentration
20-20-20 is one-third more concentrated, delivering more nutrients per pound of product
7
9
Container Growing
20-20-20 dissolves completely and feeds evenly through container media. Granular can create hot spots
4
9
Large Area Coverage
Spreading granular 15-15-15 over a half-acre is practical. Mixing 20-20-20 for that area is not
9
5
Cost per Acre
15-15-15 granular costs significantly less per acre treated than water-soluble 20-20-20
8
5

When Should You Choose 15-15-15 Fertilizer?

Choose 15-15-15 Fertilizer when you prioritize application method, large area coverage, cost per acre. 15-15-15 granular is broadcast with a spreader, fast and simple. 20-20-20 requires mixing with water

  • Application Method: 15-15-15 granular is broadcast with a spreader, fast and simple. 20-20-20 requires mixing with water
  • Large Area Coverage: Spreading granular 15-15-15 over a half-acre is practical. Mixing 20-20-20 for that area is not
  • Cost per Acre: 15-15-15 granular costs significantly less per acre treated than water-soluble 20-20-20

Learn more about 15-15-15 Fertilizer

When Should You Choose 20-20-20 Fertilizer?

Choose 20-20-20 Fertilizer when you prioritize nutrient concentration, container growing. 20-20-20 is one-third more concentrated, delivering more nutrients per pound of product

  • Nutrient Concentration: 20-20-20 is one-third more concentrated, delivering more nutrients per pound of product
  • Container Growing: 20-20-20 dissolves completely and feeds evenly through container media. Granular can create hot spots

Learn more about 20-20-20 Fertilizer

Sources

Source:Colorado State University Extension: Fertilizing the Vegetable GardenSource:Wikipedia: NPK Rating

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