Bulbs
Flower Basics
Flower Beds & Specialty Gardens
Flower Garden
Garden Furniture
Garden Gnomes
Garden Seeds
Garden Sheds
Garden Statues
Garden Tools & Supplies
Gardening Basics
Green & Organic
Groundcovers & Vines
Growing Annuals
Growing Basil
Growing Beans
Growing Berries
Growing Blueberries
Growing Cactus
Growing Corn
Growing Cotton
Growing Edibles
Growing Flowers
Growing Garlic
Growing Grapes
Growing Grass
Growing Herbs
Growing Jasmine
Growing Mint
Growing Mushrooms
Orchids
Growing Peanuts
Growing Perennials
Growing Plants
Growing Rosemary
Growing Roses
Growing Strawberries
Growing Sunflowers
Growing Thyme
Growing Tomatoes
Growing Tulips
Growing Vegetables
Herb Basics
Herb Garden
Indoor Growing
Landscaping Basics
Landscaping Patios
Landscaping Plants
Landscaping Shrubs
Landscaping Trees
Landscaping Walks & Pathways
Lawn Basics
Lawn Maintenance
Lawn Mowers
Lawn Ornaments
Lawn Planting
Lawn Tools
Outdoor Growing
Overall Landscape Planning
Pests, Weeds & Problems
Plant Basics
Rock Garden
Rose Garden
Shrubs
Soil
Specialty Gardens
Trees
Vegetable Garden
Yard Maintenance
What Does 13-13-13 Mean on Fertilizer?
What Does 13-13-13 Mean on Fertilizer?. The three numbers you find on all commercial fertilizers make up what is known as the N-P-K ratio. The name comes from the chemical symbols for the elements that the numbers represent. The three numbers, such as 13-13-13, on a fertilizer bag reflect the percentage of nitrogen (N), phosphorus (P) and potassium...
The three numbers you find on all commercial fertilizers make up what is known as the N-P-K ratio. The name comes from the chemical symbols for the elements that the numbers represent. The three numbers, such as 13-13-13, on a fertilizer bag reflect the percentage of nitrogen (N), phosphorus (P) and potassium (K) in the mixture -- always in that order. The proper N-P-K ratio promotes healthy plant growth.
Understanding Nutrients
Plants need nitrogen, phosphorus and potassium in greater quantities than any of the other soil-based plant nutrients. Nitrogen, the first number in the N-P-K ratio, helps plants gain energy and supports strong, leafy green growth. Phosphorus, the second nutrient, helps plants take up nutrients and promotes blooming and fruit development. Potassium, the third nutrient, helps plants absorb other plant nutrients and encourages overall plant health. When all three numbers on a fertilizer are the same, such as 13-13-13, the product is called a balanced fertilizer.
Examining the Numbers
A balanced fertilizer, such as 13-13-13, is also considered a complete fertilizer because it contains all three of the essential primary nutrients. A 100-pound bag of 13-13-13 fertilizer contains 13 pounds of nitrogen, 13 pounds of phosphorus and 13 pounds of potassium in the form of potash. Fertilizer recommendations often call for actual pounds of nitrogen. With a 13-13-13 fertilizer, it would take 7 1/2 pounds of the 13-percent nitrogen fertilizer to deliver 1 pound of actual nitrogen.
Testing Soil First
Before you add a 13-13-13 fertilizer to your garden, test to determine the level of available nutrients in soil. Soil tests determine if soil is lacking any nutrients, which determines the proper fertilizer N-P-K ratio to apply. Although plants require nitrogen, phosphorus and potassium for healthy growth, too much nitrogen can cause problems. It reduces flowers and fruit and may increase susceptibility to disease and insect damage. However, phosphorus and potassium are harder for plants to absorb from soil and rarely cause problems from overfertilization. Your soil may not need all three nutrients your 13-13-13 fertilizer holds.
