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Best Organic Garden Fertilizer

Feed the soil that feeds your plants. Learn how to make the best organic garden fertilizer with a few simple ingredients, and understand when to apply it for healthy soil and plants. 

The organic fertilizer mix recommended by garden guru Edward C. Smith (recipe below) is often thought of as the best organic garden fertilizer. It provides all of the essential macronutrients and many of the micronutrients garden soil needs. 

Best Organic Garden Fertilizer

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Before adding any fertilizer, it’s important to have a basic understanding of soil fertility

Plants need several nutrients to grow well​. These nutrients are normally divided into two groups: macronutrients and micronutrients

The macronutrients needed by plants are carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur. 

Some common micronutrients needed by plants are boron, copper, iron, manganese, molybdenum, and zinc. Micronutrients are just as important as macronutrients, just needed in smaller amounts. 

Best Organic Garden Fertilizer

Which nutrients do I need to provide for my garden?

Although all the macronutrients are important, there are a few that aren’t readily provided by air and water – these are nitrogen, phosphorus, and potassium

These 3 elements are often used up by growing plants and may need to be replenished. These are the nutrients listed as 3 numbers on fertilization labels N – P – K. 

Nitrogen is an important part of the best organic fertilizer

Best Organic Garden Fertilizer

Nitrogen is crucial for healthy leafy growth. Plants use more nitrogen than any other nutrient. Nitrogen is also a key element of chlorophyll.

Plants grown in soil deficient in nitrogen have overall poor plant health. The leaves on nitrogen deficient plants are often light green or yellow. 

Too much nitrogen in the soil is also not good for plants. Excess nitrogen may result in excess vegetation without blossoms or fruit. Greens may be bitter when too much nitrogen is present.

Organic sources of nitrogen include: blood meal and fish emulsion.  

Phosphorus is an important part of the best organic garden fertilizer

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Phosphorus encourages strong root growth. Adequate phosphorus in the soil encourages the development of flowers, fruits, and seeds. Phosphorus also helps plants with photosynthesis. Phosphorus is essential for the plant’s general health and overall vigor. 

Plants grown in soil deficient in phosphorus may have purple leaves. A lack of phosphorus is also a cause of poor root growth and poor overall plant growth.

Too much phosphorus can inhibit the growth of mycorrhizal fungi – an important soil organism.

Organic sources of phosphorus include rock phosphatebone meal, and guano.

Potassium is an important part of the best organic garden fertilizer

Best Organic Garden Fertilizer

Potassium increases the yield and quality of plants. This essential macronutrient also helps plants resist disease and stress. Sufficient potassium strengthens root systems and helps prevent wilt. Potassium also helps regulate photosynthesis and aids in the formation of starch. Adequate potassium is crucial for good soil health. 

Plants grown in soil deficient in potassium may seem small, weak, or thinner than normal. A lack of potassium is not always easy to spot. Potassium deficient fruits may be small or lack flavor.

Organic sources of potassium include greensand and kelp meal.

The best organic garden fertilizer recipe:

Each batch makes enough to amend 2-3 cubic foot of new soil mix.

1/3 cup blood meal (nitrogen)

1 tablespoons azomite (trace elements)

1/3 cup rock phosphate (phosphorus)

1/3 cup greensand (potassium & trace elements)

Adding a balanced organic fertilizer to your soil mixture for raised beds helps give plants the food they need to grow and thrive in your garden. You are feeding the soil that feeds your plants. 

For square foot gardens: add approximately 1 cup per 7 square feet, or 1/7 cup per square. 

Best Organic Garden Fertilizer

When to use this organic fertilizer mix in your garden

Test soil before adding fertilizer to existing garden beds

A soil test is invaluable for discovering which nutrients your soil is lacking.

It’s important to have your soil tested at least once a year. A soil test can determine the health of your soil. This is the soil test kit I use. It’s very simple to use. 

Rather than indiscriminately adding fertilizer, it’s important to fertilize responsibly. Too much of any one element can be harmful to plants or make other nutrients unavailable to plants. Having your soil tested lets you know exactly what is going on in the soil. 

Soil testing will also help you be aware of your soil pH. Soil pH is a measure of how alkaline or acidic the soil is. The pH scale is from 1-14; 7 is neutral. Values above 7 are alkaline, and below 7 are acidic. One reason pH is important is because if the soil is too acidic or alkaline, some nutrients become unavailable for plants.

If you enjoyed this post about the best organic garden fertilizer, please share it:


Wednesday 29th of March 2023

Can you explain when to use the Alaska Fish Plant Food Fertilizer and also the Organic Liquid Kelp Fertilizer you recommend?

Patrice Nick

Saturday 18th of December 2021

MY soil is too alkaline. 8.5 How can I lower it? My vegetable garden is already established. The plants are not growing to their potential and the veggies are quiet small. Any help will be greatly appreciated. Phx AZ

Angela Judd

Tuesday 21st of December 2021

Here's an article that may be helpful with specific information:


Wednesday 28th of July 2021

Thank you for putting the best organic garden fertilizer in this article. Really helpful to all gardeners. Keep sharing more gardening and fertilizer tips.

Adam Barnes

Monday 14th of December 2020

Do you still recommend adding this fertilizer recipe to the "Growing in the Garden Raised Bed Mix" from the Arizona Worm Farm?

Angela Judd

Monday 14th of December 2020

That's a good question. Yes, to give your plants a good boost from the start, I think it's a good idea to add some.