Amazon.com : Greenway Biotech, Inc. Lettuce Fertilizer 8 15 36 Powder Water Soluble with Chelated Micronutrients for Lettuce Kale Spinach Microgreens Helps Prevent Tip Burn Hydroponics or Soil 1 LB : Patio, Lawn & Garden LESCO 18 3 6 Liquid Fertilizer 50% Controlled Release Nitrogen with Iron MasterBlend 8 15 36 Lettuce Formula 25 lb. Custom Hydro Lettuce Fertilizer 8 15 36 Water Soluble Leafy Green Formula 1 Pound by Greenway Biotech, Inc. Understanding NPK: The Three Key Nutrients in Fertilizers When you look at a fertilizer label, you'll often see three numbers. These numbers stand for nitrogen (N), phosphorus (P), and potassium (K). Each