What fertilizer numbers mean - HowtoGardenLawn.com's fertilizer infographic with pictures and an explanation of nitrogen, phosphorus and potassium analysis in fertilizer bags

Fertilizer How To – What Do the Numbers on a Fertilizer Bag Mean?  What Fertilizer to Choose?

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We hope you liked HowtoGardenLawn.com‘s fertilizer number infographic.  I think it’s easy to agree:

Fertilizers are hands down the most economic and fastest way to benefit your lawn and garden!

By adding fertilizer properly, your lawn, plants, flowers, and trees will grow faster, stronger, healthier and greener.  If you’re looking for information on how to fertilize the right way, including how to use fertilizer numbers and how to choose a fertilizer, you’ve come to the right place!  We’ve also added some recommended products based on typical lawn and garden fertilizing needs.

What Fertilizer Numbers Mean:

There are three numbers in the form of N-P-K on a fertilizer bag which represent the main elements found in the fertilizer.

N – represents the Nitrogen % content in the bag.

P – represents the Phosphorus % content in the form of phosphate (P2O5).

K – represents the Potassium % content in the form of potash (K2O)

These numbers are commonly referred to as the nutrient analysis of the fertilizer.  For example, a 4-4-4 fertilizer would contain 4% N, 4% P, and 4% K.  Depending on your planting needs, you may need varying amounts (or none) of the above nutrients.

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How to Choose Fertilizer Based on Fertilizer Numbers?

Caution:  Your choice in fertilizer will depend largely on your objective, geography, climate and circumstance.  Choosing the wrong fertilizer or applying fertilizer under the wrong conditions may damage your lawn, garden or plants.

It is helpful to know the effects N, P and K have on plant growth in order to meet your fertilizer needs.

N – used to promote leaf & foliage growth and helps plants stay green.  Great for mature lawns!

Nitrogen in fertilizer helps leaf and foliage growth

Phosphorus or phosphate in fertilizer helps build roots, fruits and flowers.

P – helps plants grow roots, fruits and flowers.  Great for new lawns and or to “super bloom” plants!

Potassium or potash in fertilizer helps overall plant growth and health.

K – overall plant health and growth

HowtoGardenLawn.com recommends performing a soil test in order to determine exactly which nutrients are in abundance and which are deficient before your start your fertilizing project.

How to Perform a Soil Test?

soil test is a process by which the quantity of nutrients and elements needed for plant growth are measured within the soil.  In other words, a soil test checks to see if your plants or soil have enough of the following elements – nitrogen, phosphorus, potassium, calcium, magnesium, zinc, sulfur, sodium, copper and manganese.  Soil tests also typically check for pH, exchangeable acidity and humic matter (the major organic parts of soil/humus, peat and coal) which dictate whether you need to add peat moss and lime to your soil.

Two recommended options that you can easily purchase are a soil test device and a soil test kit below:

For those of you mad scientists out there who prefer chemicals over gadgets, try this to get an even more accurate chemical analysis of your soil:

What Fertilizer to Choose?

With fertilizer numbers and the soil test in mind, here are HowtoGardenLawn.com‘s fertilizer recommendations, including some common fertilizer numbers :

New Lawn or After Overseeding:  Starter lawn fertilizer high in phosphorus – e.g., 10-18-10 (Scotts Turf Builder Starter Food for New Grass Plus Weed Preventer)

Mature Lawn:  Lawn fertilizer high in nitrogen and low in phosphorus – e.g., 30-0-3 (Scotts Turf Builder Lawn Food) or if you want a dummy-proof, organic fertilizer choose Milorganite (Organic NON-burning fertilizer)

Fall/Autumn Lawn Fertilizing Before Winter:  Lawn fertilizer high in nitrogen, low in phosphorus, and medium in potassium – e.g., 32-0-10 (Scotts Turf Builder Winterguard, 15,000 ft. coverage)

General Plant Growth: General plant fertilizer – e.g., 4-4-4 (Jobe’s Organics All Purpose Fertilizer with Biozome, 4-4-4 Organic Fast Acting Granular Fertilizer for All Plants, 4 pound bag)

Super Bloom Plant Growth:  Plant bloom booster – e.g., 10-30-20 (J R Peters Inc 51024 Jacks Classic No.1.5 10-30-20 Blossom Booster Fertilizer)

Tomato or Vegetable Garden:  e.g., Miracle-Gro 3002610 Shake ‘N Feed Tomato, Fruits and Vegetables

Potted Flowers or Flower Garden:  e.g., Miracle-Gro 3001910 Shake ‘N Feed All Purpose Continuous Release Plant Food

For Evergreens or other trees:  Try a fertilizer stakes or spikes.  e.g., Miracle-Gro Fertilizer Spikes for Evergreens

How to Fertilize?

How to apply fertilizer on lawn has been covered in our post: How to Fertilize Lawn? When to Fertilize? DIY Fertilizer FAQ’s

Clear as mud?  Hope the fertilizer infographic and how to choose fertilizer information helped!  Let us know if you have any further fertilizing questions.