best organic fertilizers

Guide to the Best Organic Fertilizers

What the best organic fertilizers for long-term garden health?  We’re going to cover the three essentials elements that the best organic fertilizers have, and those top organic fertilizers that meet the criteria.

We’ll also cover the secondary or “runner up” organic fertilizers that are also great for your garden, whether you are growing awesome tomato varieties or potatoes.

A healthy soil nurtures healthy plants.  We want to utilize the best organic fertilizers that will help our plants grow better, taste delicious, increase their resistance to plant diseases, reduce stress due to heat and cold, store longer and of course, increase the yield if we are growing food.

What Makes the Best Organic Fertilizers?

The best organic fertilizers are those that no only feed your plants with the nutrients they need, but build up the soil so that they function optimally so that your plant can achieve their maximum potential.

This includes other soil benefits, such as:

Improving air spaces in the soil

Allowing for nutrients to be held to the soil particles for availability to the plants throughout the growing season

Improved water permeability

Support the beneficial soil microbes necessary for plants to flourish

Best Organic Fertilizers

So what are the best organic fertilizers to use?

Defining what is an "Organic Fertilizer"

First let’s define what an “organic fertilizer” is:

The US Department of Agriculture states that to be an “organic fertilizer” the fertilizer must be derived from animal matter, manure or vegetable matter.

Naturally occurring organic fertilizers include animal wastes from meat processing, peat, manure, slurry, and guano (dung).  It is not derived from petroleum, as is the case with synthetic fertilizer.

The Best Organic Fertilizers Serve Multi-Purposes

  1. Provides Nutrients to the Plants
  2. Feeds the Soil Microbes that Support Plant Growth
  3. Improve the Growing Conditions in the Soil for Optimum Plant Health

1. Best Organic Fertilizers: Provides Nutrients to Plants

Organic fertilizers provide nutrients to the soil

Improving Soil

Most of us just consider fertilizers for the sole purpose of providing nutrients to our plants, and are either unaware or ignore the importance of feeding the beneficial soil microbes and improving soil conditions.  

If that’s you, it’s not so unusual, since that is only the extent of what major fertilizers advertisers want you to know.

Long-Term Sustainability

To really build a long-term, sustainable and healthy garden, one that is not continuously on the verge of stress for lack of nutrients or weakened and susceptible to diseases, one should look beyond just the plant nutrient aspect and considering utilizing fertilizers that provide multiple benefits. Compost is one of the best natural fertilizer there is!

The best organic fertilizers serve multi-purposes.

Plant's Bank Account

The planting medium, whether it be native soil or a potted mix, is the bank account for our plants. The bank needs to have nutrients in them, and available when the plants need the nutrients, in order to grow and to resist diseases.

N-P-K Essentials

So any fertilizers should not only have the major nutrients – Nitrogen, Phosphorous and Potassium, but micro and trace nutrients as well.  The key is to have these nutrients available when the plant needs it.

  • The best organic fertilizers support release of nutrients to the plants when the plants go to the ATM.
  • Synthetic fertilizers do not do this.  It’s an all or nothing, leaving the plant hungry later in the season.

2. Best Organic Fertilizers: Feed the Soil Microbes that Support Plant Growth

When we select the best organic fertilizers, they feed our soil microbes that are the “plant helpers” that go out and find nutrients and water for the plants.

You may not have heard of this concept before, but there is a whole Soil Food Web that lies beneath our feet and in our soils that is responsible for long-term plant health.

The best organic fertilizer feed our soil microbes

When we feed our soil microorganisms we provide the “Probiotics for Plants” that help the plants produce more, be resilient to diseases, and stay healthy throughout the growing season. Mycorrhizal fungi is one of the key micro-organisms that you can add to your garden.

Probiotics for Plants: Feeding Soil Biology

  • Increases Plant Yields
  • Promotes Disease Resistance
  • Stronger, Healthier Plants

Our soil microorganisms include not only the well-known earthworm that does an amazing job at aerating our soil, but beneficial fungi (mushrooms) and bacteria that are the real workers in the soil world.

Beneficial mycrorrhizal fungi help the plant take up more phosphorous than if they were not present.  Soil bacteria help the plant resist plant diseases such as leaf mold and potato canker.  The more we feed our soil microorganisms the stronger and healthier our plants will be.

3. Best Organic Fertilizers: Improve the Growing Conditions in the Soil

best organic fertilizer improves soil conditions

Choosing the best organic fertilizers also improve growing conditions in the soil so that the plants are able to be healthier and produce more.

Unlike artificial fertilizers an organic fertilizer can improve growing conditions.

Here’s just a few benefits that an organic fertilizer rich in organic matter can do:

  • Reduce drought stress – Improved water holding capacity
  • Improved ability for soil to retain nutrients within the root zone
  • Transform toxins into harmless states
  • Provide food to the soil microbes
  • Improve plant resistance to disease (due to presence of beneficial microbes)
  • Sequester carbon
  • Improve soil aeration (soil texture) – better root depth, better water filtration

Top Best Organic Fertilizers


Getting started composting

The benefits of compost are exceptional and meet all three criteria for the best organic fertilizers.

  • It provides a slow-release nutrient source for the plants, becoming available when your plant needs it.
  • It feeds the soil biology
  • It provides a multitude of soil benefits including water & nutrient retention, toxin transformation and improved aeration

Compost can be purchased or made. If you really want to optimize your plant growth, learn to make compost at home.

Vermicompost | Wormcastings

Worm castings are also called vermicompost and is also an amazing organic fertilizer. Dubbed the “superfood” within the best organic fertilizers category, worm castings provide nearly 9 times the plant available nutrients than artificial fertilizers.  They are great when growing tomato varieties.

Also high in organic matter they provide great soil building material.


Wormcastings are now commercially available in most plant nurseries, but since the benefits are provided due to their high biological activity, worm castings should not be dry or crumbly, or saturated or stinky.

Purchased worm casting should be slightly moist. Even better, start a worm bin at home for all your food and paper scraps.

Other Great Organic Fertilizers

Runners Up: Best Organic Fertilizers

Compost and worm castings make the best organic fertilizers that meet all three criteria. There are other great organic fertilizers that may fall short of meeting all three criteria, but nonetheless provide a supporting runner up roles in the organic growing world. Here’s a few to consider:
Organic Fertilizer Provides Nutrients Supports Soil Biology Improves Soil Growing Conditions
Fish Hydrolysate Nitrogen Yes
Sea Kelp Potassium, Trace Minerals Yes
Bat or Seabird Guano Phosphorous
Chicken manure Nitrogen
Azomite Trace minerals
Humic & Fulvic Acids Yes Yes
Greensand Yes
Crab Shell Meal Yes
Sulfate of Potash Potassium, Sulfur
Rock Phosphate Phosphorous Yes
Bone Meal Phosphorous
Feather Meal Nitrogen

Recommended Products

Synthetic Fertilizers: Why They Are Bad for Your Soil

Adding synthetic fertilizers such as Miracle Grow only provide short term benefits for your plants and you may find yourself having to re-apply continuously throughout the growing season. This costs money and takes up your valuable time.

Synthethic fertilizers are harmful to your plants soil and soil biology
Gary Larson. Salts are hard on your plants, and the beneficial microbes

Other slow release fertilizers such as Osmocote are petroleum based as well (synthetic) and just provide benefits for one growing season while doing nothing to build better soil and growing medium for your plants.

So What's Wrong With Synthetic Fertilizers?

Industrially produced fertilizers are commonly used in major agricultural operations, so what’s wrong with that?

Here's the Essential Difference

Synthetic fertilizers are not organic and may actually be harming soil health as well as impact water quality in streams and wells.

Lost in the Soil

When the industrially produced fertilizers are added to the soil, they are essentially used up immediately or lost as they flow through the soil profile.  So about 20% are used by the plants and the remaining 80% is wasted and flows down the soil profile, eventually reaching the groundwater. Many wells get contaminated due to excess use of fertilizers.

Feast or Famine

Because they are not organically based they do not adhere to soil particles and are not available to the plant for later use. It’s a “feast or famine” situation.  Not the best use of a fertilizer.

Algae Blooms & Fish Kills

Excess phosphorous applied to soils are not typically plant available.  Fertilizers high in phosphorous get washed into rivers and lakes and cause algae blooms. These algae in turn use up oxygen in the water causing fish kills in extreme situations.

Salt: The Great Dehydrator

Did you know that synthetic fertilizers are a salt?  Salt acts as a desiccant (dehydrator). Adding too much salt in the form of synthetic pelletized fertilizers actually draws moisture away from the plant. It also kills the beneficial microbes responsible for helping plants find water and nutrients.

Synthetic Fertilizer: The "Crack Cocaine" for Plants

So once these salts are added, it’s like the “crack cocaine” for plants – you kill the beneficial microbes that help the plant, leaving only the dependency for more artificial fertilizers in order to keep the plant alive. It also weakens the plant, making it more susceptible to diseases.

In Contrast: Best Organic Fertilizers

The best organic fertilizers work with in harmony with nature and provides long-term soil and plant health when the plant needs it, so that you won’t have to apply fertilizers over and over throughout the growing season.

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What are the best organic fertilizers for my garden? Guide to the Best Organic Fertilizers

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