Compost Tea NPK Values

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Robert Pavlis

Compost tea is reported to be great for growing plants and some companies even call it a compost tea fertilizer. What is the NPK value of this magic potion?

I started this post about a year ago and at that time there were many products on the market but I could not find one that provided the Compost Tea NPK value. I checked again today and was surprised that the number of compost tea products available is down significantly. Maybe it was too expensive to ship all that water around the country? Maybe it did not work and people stopped buying the product?

Interestingly, the number of commercial DIY kits for making your own tea is up significantly. When you click on Google images for ‘bottles of tea’ you are taken to pages selling kits. Even with kits the same question needs to be asked. What is the NPK value of the tea these kits produce. Very few of the manufacturers I looked at provided such information, but many did say their compost ingredients were the best. Easy to say if you don’t give any data.

Even if you are not interested in compost tea – the following discussion will show you how companies are misleading consumers.

Plant Science for Gardeners by Robert Pavlis
What is the NPK value of compost tea?
What is the NPK value of compost tea?

Contact the Manufacturers

I decided to contact several manufacturers of compost tea (the liquid form, not the kits) and asked them for information about their NPK values. Only one company thought this question was worth an answer, and that was Southern Organics. Compliments to them for caring about their customers.

Here is the email I sent:

“I am interested in your compost tea. What is the NPK value for this product?”

At the time of contact they had only one compost tea on their web site called Ultimate Compost Tea. I thought the above question was a fair one since their advertisement for the product says “Ultimate Organic Compost Tea a highly concentrated liquid ……. that injects beneficial microbial life into the soil and the foliage of plants, improving soil structure and adding nutrients, making your plants healthier, stronger, and more robust.”

If it is highly concentrated with nutrients – they must know the NPK value!

Their email reply is as follows:

“Unfortunately we are not allowed to state the NPK level because we do not register that particular product as a fertilizer.  The NPK is negligible though.  It is roughly 1 – 1.5 % Nitrogen.
 Its power to chelate and deliver macro-nutrients is what makes the product so valuable.  It makes a fertilizer much more effective, longer lasting and feeds the soil and microflora.”

It is illegal to tell me the NPK value because it is not considered to be a fertilizer! I don’t believe that it is illegal. I do agree it is not a fertilizer. The reply suggests that the NPK value is 1.5-0-0. However, in subsequent emails they sent me the chemical analysis data for their starting material which has 1.5% nitrogen, based on the dry weight. So that number is not the value once it is diluted in water to make tea. Based on the amounts of Humic acid in the starting material and the finished product, the Nitrogen in the Tea is closer to 0.1%. The starting material has no P and K. The NPK value is therefore 0.1-0-0, at most.

A fertilizer with an NPK value of 0.1-0-0 has virtually no nutritional value for your plants. That is one reason they don’t call it a fertilizer.

The Power of Chelation

The second part of the email response points out that the “power to chelate … makes the product valuable”. Let’s look at this.

I asked some clarification questions and got the following response:

“It helps fertilizer last longer by a process called Chelation.  See –

“The colloids in the humic, fulvic and ulmic acids also help keep nutrients from slipping away much like the chelation properties.
 While NPK is important and considered the 3 macro nutrients, there are 72 trace elements and nutrients that are just as important as NPK.  Depending on the crop or species a deficiency in a single micro nutrient can be as detrimental as a deficiency in a macro nutrient (NPK).  
 The product is also extremely high in vegetative carbon.  Carbon source is more important than NPK.  It plays a vital part in photosynthesis.  Soil carbon is the most important factor of soil health.  It increases the Cation Exchange Capacity. “

They have now introduced some scientific terms like chelation and colloids that most people don’t understand – which is good for them since it allows them to present more false claims – a common tool used by marketing departments.

When fertilizer is added to soil, P, K and some other minor nutrients tend to bind tightly to soil. What this means is that even though your soil has enough nutrients, plant roots can’t easily get to them. A chelating compound will act like the soil and also hold nutrients, but it binds loosely to them so that roots can use them.

Chelation is not needed for nitrogen since it does not stick to soil, and their product has no P and K. so is chelation really an important feature of their product?

Chelation will NOT make fertilizer last longer. It can however make it more accessible to plants and it might reduce the speed of leeching. But once an ion is absorbed by the plant it is gone – it does not last longer.

The Lies Keep Coming

Trace elements are important but are there really 72? Their lab only tests for 9 micro-nutrients and that is for the raw material, not the tea. Based on their testing they don’t know if they are in the tea. But you might as well make claims for all 72! In my post, Trace Mineral Fertilizers – How Many Nutrients Do Plants Need, I reviewed the ridiculous claims that plants need a large number of different nutrients. Plants only use about 24 nutrients.

“The product is extremely high in vegetative carbon”. Now that is interesting and is not mentioned in the product description. What is vegetative carbon? It is carbon that comes from plants. Oil would be an example of this, as would diamonds. This may seem like an odd statement, but their so called compost is actually mined from the ground and is more like coal than what most people think of as compost – but that is a topic for another post. They also say that “Carbon source is more important than NPK”. The main source of carbon for plants is the CO2 in the air. They don’t get much of their carbon from chemicals in the soil. These statements about carbon are nothing more than science mumbo-jumbo.

It says “extremely high”, but what is high? The analysis is a bit confusing but it looks like the value is about 6% carbon. Remember that this is a liquid product so most of the jug is water. Compared to compost which is 25% carbon, a value of 6% is not extremely high.

“It (vegetative carbon) plays a vital part in photosynthesis” – no it doesn’t. CO2 from the air does. But they might argue that without carbon chemicals in the plant you can’t have photosynthesis?

“Soil carbon is the most important factor of soil health” – not even close to being true. A pile of coal has lots of soil carbon, but it is not considered healthy soil as far as plants are concerned. They are probably talking about organic carbon, but if that is the case, what the heck is vegetative carbon?


A few statements from the manufacturer are true or are partially true. Chelation in soil is important. Micro-nutrients are important to plants. Humic acids are beneficial to plants – more on that in a future post.

These facts are then submersed in a bunch of mumbo-jumbo making the whole thing sound factual and scientific. A bit of science lingo lets people say all kinds of stuff and make it sound valid. That is why the internet is full of so many myths and products that add no value to the garden.

The reality is:

  • compost tea contains few nutrients – see below
  • spreading real compost or manure onto the soil provides all of the benefits of tea, at a fraction of the price.

Compost Tea NPK Value

So what is the NPK of compost tea? Here are some numbers I found.

Ultimate Tea from Southern Organics: 0.1-0-0

Cutting Edge Solutions – HumTea Original – Compost Tea: 0-0-1

Super Compost Tea: 0.02-0.2-0

Compost Tea – Does It Work: 0.2-0-0

The actual values will depend on the compost used to make the tea, but you can see from the numbers above that none of them contain significant levels of nutrients. Keep in mind that these values will be further diluted before the tea is added to the garden. Sounds a lot like homeopathic medicine!

Some proponents of compost tea say that the nutrients are not the important ingredient. It is the microbes that are the key value in compost tea. In my post, Compost Tea – Does It Work ,I look at the effect of these microbes on the growth of trees.

To date, most of the research does not support the claims made by proponents of compost tea. There is little evidence that it is any better than just using compost.

Related Posts

Compost Tea – what is it and what are the benefits?

Compost Tea – Does it Work?


  1. Photo source; Suzie’s Farm


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Robert Pavlis

I have been gardening my whole life and have a science background. Besides writing and speaking about gardening, I own and operate a 6 acre private garden called Aspen Grove Gardens which now has over 3,000 perennials, grasses, shrubs and trees. Yes--I am a plantaholic!

20 thoughts on “Compost Tea NPK Values”

  1. Talking about N.P.K levels of organic fertilizers and other organic materials is it self the myth. What happens is, if you put organic things to your soil it will become natural after about 2 Years. Then, my question, Do you people talk about N.P.K levels in a jungle? everything grows without much effort after 2Years. Best thing is to create the “Compost tea” by yourself rather than using commercial products, if you are so unsure about them.

  2. I actually did an informal experiment with vermicast tea, watering ten plants with plain, dechlorinated water and ten plants with the vermicast tea. I made sure to give all plants the same amount of sun and liquid.

    It was my observation that the ones watered with the tea did slightly worse. Perhaps I got some of the tea on the leaves and that was harmful, I don’t know.

    However, my playing around with the tea showed me that using it is not a simple process.

  3. I don’t know if this matters, but my yard only has fruit trees. I am not a “gardener”. I have over 50 fruit trees and all of them are planted in the ground with 12-20 inches of wood chips on top. I have been applying compost to the trees four times a year and pulling back the wood chips to apply the compost is radically time consuming. I have been looking into making a tea purely for the ability to pour it over the top of the wood chips and move on to the next tree. I don’t care about using less compost, I just want to feed my trees in two or three short Saturdays vs. two full weekends. Am I going to lose out on enough of the “good stuff” that I should just suck it up and keep applying the compost directly to the ground?

    • Why not just put the compose on top of the wood chips? Nature will move it to soil level. Your wood chips may decompose a bit faster this way.


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