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How to Determine if Nutrients are Truly Organic

By Chris Bond | Last updated: April 25, 2021
Key Takeaways

Your plants don’t know the difference between organic and chemical nutrients, but you should. Follow Chris Bond’s tips if you’re seeking truly organic nutrients for your garden.

With so many choices available on the market, it can be difficult for growers to discern whether a product is, in fact, organic. This can be especially true for nutrients and fertilizers. Manufacturers can make any number of claims on their product labels assuring the quality of their ingredients, but how can you really know they are truly organic? What does the word organic really mean as it relates to horticultural amendments?

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Organic vs. Conventional Nutrients

It is not always easy to ascertain what makes a nutrient organic versus conventional. Is it the numbers? The source of the nutrients?

Organic nutrients almost always have lower fertilizer values printed on the bag or container and are almost always more costly than their conventional counterparts. Conventional or chemical nutrients are typically higher in fertilizer value and seemingly much cheaper. There are several reasons behind this. Plants don’t know the difference between, for instance, a nitrogen source that is organic in origin or chemical. They absorb nitrogen as NO3 (nitrate) or NH4 (ammonium) regardless of its source. The differences lay in how those sources break down and become available to the plants. The same is true for organic potassium and phosphorus sources. Regardless if the source is organic or not, it must be converted to or supplied as K2O and P2O5 respectively to be absorbed.

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Both organic and non-organic nutrients will supply these nutrients in their absorbable forms.

Organic nutrients are not easily or quickly absorbed by plants. They are slowly released by virtue of natural decomposition and natural processes in the soils. All the soil bacteria, microbial organisms, and beneficial fungi act as a digestive system converting nutrients into a form the plant can readily take up. This happens more quickly in warmer months than in cooler months, but it can mean a much longer and ready supply of nutrients as your plants need them.

Read also: How to Boost Living Soil with Organic Amendments

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Chemical or conventional fertilizers, on the other hand, are almost always water soluble. They break down and are readily available as soon as they get wet. Unfortunately, the plants rarely get to use all the nutrient package delivered to them even though high nutrient concentrations are often provided by conventional fertilizers. Plants can only take so much of any nutrient at any one time.

With non-organic nutrients, this excess nutrient is either leached down into the soil, or worse, taken away with run-off activity and delivered into water sources or other unwanted locations. So, what may seem like a bargain often isn’t when it comes to comparing prices on organic versus non-organic nutrients. Yes, you may seemingly be getting much more value for your dollar with conventional fertilizers, but isn’t it more important how much of that nutrient your plants or crops get to use? There are several other important differences between organic and non-organic nutrients besides how they are absorbed and how much they cost.

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Organic nutrients generally benefit the soil, as opposed to just delivering a meal to your plants. They can improve water movement and water-holding capacity throughout the soil. They can also contribute to better soil structure and cation exchange capacity (CEC).

Because of their origin from plant, animal, or mineral sources, as opposed to chemical or petroleum bases, they often also supply needed micronutrients to plants. Non-organic nutrients can sometimes leave or build up a crust on the soil that can make it difficult for water to get absorbed and not just shed off.

Examples of Organic Nutrients

As mentioned above, organic nutrients are those nutrients derived from nature. They can be derived from mineral, plant, or animal sources. They sometimes come in the form of composted material such as manure (manure should never be used hot as it can burn plant crops — it should be composted or aged prior to use) or moderately processed substances such as meals (e.g. kelp meal, bone meal, blood meal, etc.). The following is a list of several different sources of truly organic nutrients (by no means exhaustive…):

Urea FertlizerUrea Fertilizer

Organic Sources of Nitrogen (N):

  • Urea (Urine) — this typically ranges between 42 and 46 percent nitrogen. This is an exception to the notion of organic nutrients being typically low in fertilizer or nutrient value. This should be used carefully as even though it is organic, it can still burn plants if used in too high of a concentration.
  • Poultry Feathers — usually about 12-15 percent nitrogen. Sometimes sold as feather meal.
  • Blood Meal — this is typically at 12.5 percent nitrogen and is generally derived as a byproduct
    of bovine slaughter.
  • Dried Blood — same as blood meal, with 12 percent nitrogen.


Rock PhosphateRock Phosphate

Organic Sources of Phosphorus (P):

  • Rock Phosphate — this can vary depending on its origin between 20 and 33 percent phosphorus.
  • Colloidal Phosphate — this ranges between 17 and 25 percent phosphorus. It is a type of soft rock phosphate that also contains calcium.
  • Bone Meal — between 15 and 27 percent phosphorus, this too is often derived as a byproduct of the slaughter industry and is usually ground bovine bones.


Kelp MealKelp Meal

Organic Sources of Potassium (K):

  • Kelp — usually between four and 13 percent potassium. There are various formulations of seaweed fertilizers on the market rich with other micronutrients as well.
  • Wood Ash — generally ranges between three and seven percent potassium. Wood ash also contains calcium.
  • Granite Meal — this ranges between three and six percent potassium and is a byproduct of mining operations.
  • Greensand — this is typically about five percent potassium and is a type of marine sand which also improves soil structure.

There are, of course, several other nutrients needed for plant growth such as calcium (Ca), which can be derived from organic sources. Some of these sources include materials from the sea such as clam and oyster shells or mined materials such as dolomite (limestone) or gypsum. All these organic sources of calcium typically deliver up to or beyond 30 percent calcium. Other organic sources of nutrients have multiple benefits. Burned eggshells have trace amounts of phosphorus and potassium in addition to calcium. Fish emulsion is a great source of organic nitrogen, but also has some phosphorus and potassium.

Read also: Organic Cannabis & the Cannabis Certification Council

When soil pH needs to be adjusted, there are several organic options for that as well. If the pH needs to be adjusted, some truly organic nutrients or amendments include peat moss, sulfur (S), and cottonseed meal. Wood ashes or ground limestone (dolomite) are both excellent sources of calcium and are also effective in raising pH.

There are thousands of possibilities for organic sources of nutrients, all which could be approved for use in organic plant or food production. It is important to note some items may themselves be organic or contain organic ingredients but contain some other non-organic aspect which would render the whole product to be considered non-organic. Knowing how to read a label properly or looking for third-party certification on a product can help the grower know if he or she has an organic nutrient.

Certifying Agencies

In the world of organic foods, such as those you might find at your local grocery store or farmer’s market, there are several government and third-party certifiers whose sole role is to ensure the organic integrity of a food product. When it comes to organic fertilizers or nutrients themselves there is only one independent verifier: The Organic Materials Review Institute (OMRI). For our friends in the Great White North, there is OMRI Canada. No product can legally claim to be truly organic if that claim has not been verified by OMRI.

Organic Materials Review Institute (OMRI) Logo

OMRI is an independent, nonprofit organization that reviews soil amendments, fertilizers, and any other product intended for use in certified organic food production, from farming to processing. It uses the National Organic Standards as the standard to compare all manufacturer’s product claims. Any nutrient or fertilizer with any of the following language can assure the grower that they have a truly organic product in their hand:

  • This fertilizer product is allowed for use in organic production.
  • Meets National Organic Program (NOP) requirements for organic production.
  • Suitable for organic farming.
  • Acceptable for use in organic production.
  • Meets the requirements of the National Organic Program for use in organic production.
  • This product is listed by the Organic Materials Review Institute.

It should be noted OMRI has not reviewed all products on the market.

A manufacturer must submit its products for review by OMRI. There may be products that indeed fit the bill of truly organic but cannot be sold as such until they have been approved. Similarly, there may be products making an organic claim, but have not been reviewed by OMRI. These products should be viewed suspiciously. While OMRI-approved products do not represent 100 percent of the truly organic products that are on the market, growers who are not sure of the authenticity of a product’s claim should stick with those products bearing the OMRI or the OMRI Canada label to ensure they have truly organic nutrients.

Read next: 7 Ideas to Create an Eco-Friendly Garden

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Written by Chris Bond | Certified Permaculture Designer, Nursery Technician, Nursery Professional

Profile Picture of Chris Bond

Chris Bond’s research interests are with sustainable agriculture, biological pest control, and alternative growing methods. He is a certified permaculture designer and certified nursery technician in Ohio and a certified nursery professional in New York, where he got his start in growing.

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