Organic Cannabis Nutrients: Composting

Composting is a cheap and effective way of making your own organic nutrient-rich soil without spending money.
17 August 2020
6 min read
Organic Cannabis Nutrients: Composting

  • 1. What is composting?
  • 2. Why compost?
  • 3. Benefits of composting
  • 3. a. Good for the environment
  • 3. b. Recycles waste
  • 3. c. Adds beneficial microorganisms to your soil
  • 4. The basics
  • 4. a. Composting bin
  • 4. b. Organic matter
  • 4. c. Taking care
  • 4. d. Patience
  • 5. What should i compost?
  • 5. a. What not to compost?
  • 6. How to use my compost?
  • 7. In conclusion

Composting is an organic method of providing nutrients to the soil, this can not only result in better-tasting flowers but will help you reduce waste, it’s a win-win situation for everyone.

1. What is composting?

Composting consists of a process that turns food scraps into nutrient-rich soil, this happens because the microorganisms break down the scraps and make the nutrients available for plants to absorb.

The process of composting relies on bacteria, moisture, and oxygen, by having these elements together, and the proper organic matter you provide the perfect environment for the bacteria to break down the organic material which creates heat.


Composting: what is composting?

Composting allows you to make a nutrient-rich soil with left-over food scraps.

The heat emitted helps microorganisms1 “activate” and stat decomposing the organic matter, while oxygen and moisture accelerate decomposition.

This way of reusing food waste isn’t exclusive to cannabis, it has been used for years and years by cultivators who want to reduce waste while also benefiting, either by saving money or developing a richer soil.


2. Why compost?

Composting is a cheap and easy way of making soil, when done properly you will end up with a living ecosystem that contains all the macro and micronutrients (and even more) than what you will get when buying organic nutrients at a grow shop.

Making compost not only improves the texture of soil but also acts as a slow-release nutrient source which, unlike synthetic nutrients, won’t burn your plants, by doing this you’re not only feeding your plants with top-quality nutrients but are also helping reduce the waste that goes into landfills.

3. Benefits of composting 

Good for the environment

Because you are using a natural alternative to synthetic nutrients you’re helping reduce chemicals in the soil and even though it may not seem like a lot, you’re making a difference.


Composting: benefits

Composting has benefits not only for the grower but also for the environment.

Composting helps soil hold carbon dioxide, this decreases gas emissions, revitalizes exhausted soils, and reduces erosion.

Recycles waste

Composting can reduce up to 30% the amount of waste you produce. This makes a huge difference because when your kitchen scraps go to a landfill they don’t have the appropriate conditions to decompose and end up producing methane, which is toxic to us.

Adds beneficial microorganisms to your soil

Microorganisms help aerate the soil, they break down the nutrients to make them more available and can prevent plant disease.

4. The basics

You don’t really need a lot to start from scratch, the basic materials are a composting bin and the scraps you need to start the process, although something you will need and cannot buy it is patience and taking good care of the microorganisms.

Composting bin

To start composting you really don’t need a lot, first, you need to know where you want to do it. Composting can be done indoors in a plastic bin, wooden box, or in a cube made out of bricks, or outdoors on top of a plastic sheet or directly on the soil. 


Composting: compost bin

You can compost anywhere as long as you have the basic structure.

The place where you’re be going to compost can easily be done by yourself and doesn’t need to be fancy at all, as long as you build a bin-like structure that can be covered to keep the moisture in you’ll be fine.

Organic matter

Compost consists of decomposing organic matter1 to make the nutrients available in the soil so the organic matter is vital for your it to work, you can choose which fruits and vegetables among other things you compost but in general there are two types of organic matter: Green matter and brown matter.


Composting: sources of NPK

It's essential your composting contains a balance between carbon and nitrogen to make sure your plants grow properly.

A balanced ratio between both of them is essential for the microorganisms to thrive, there isn’t a specific type of fruit that’s better. If you’re growing cannabis you have to provide Nitrogen, Phosphorus, and Potassium-rich scraps which are the macronutrients and can be found on:


  • Nitrogen: Lettuce, spinach, arugula;
  • Phosphorus: Eggshells, manure;
  • Potassium: Banana, cucumbers, cabbage.

Remember that organic matter attracts flies and cockroaches which can lay their eggs in your compost bin, so to be safe have a lid, or a mosquito net on top to avoid this.

Taking care

Inside the bin, there are living microorganisms so you should make sure they’re indeed alive.

Every 1-2 weeks you have to make sure your compost is humid, remember that too much water may kill the microorganisms but make sure it’s properly humid and if not, water it lightly.


Composting: watering your compost

Make sure your compost is humid but not soaked, especially if you vermicompost.

Your compost bin doesn’t need too much sunlight, ensures they’re under the shade, and have proper drainage because decomposition produces liquid that can end up drowning the microorganisms.

If you want to accelerate the process even more, you can vermicompost, this process uses worms that will eat the food scraps and will produce humus (aka worm castings).


Out of everything, this is the hardest part. Composting takes time, it’s not going to be ready for use overnight, the decomposition process takes at least 1 month so be patient, the longer you allow the microorganisms to work, the more concentrated it will be so let them do their thing is essential.

4. What should I compost?

What you put in your compost depends on what you aim for and what you can find but have in mind that all compostable materials are either carbon (brown matter) or nitrogen-based (green matter) so you need to have a balance of around 50/50 for your composting to work.


Composting: what to compost

Carbon and nitrogen are super important to activate and continue decomposing the food scraps, leaves and everything else you are composting (Image By David Dewitt).

Green matter2 provides nitrogen and is a source of protein whereas brown matter is carbon-rich which helps the microorganisms decompose the scraps and also helps aerate the compost bin.

Here’s a general guideline of green and brown matter you can use in your compost bin:


Carbon (brown matter)CardboardCorn cobsDry leavesNewspaperSawdustHayWood chips
Nitrogen (green matter)Coffee groundsFruits and vegetablesGrassSeaweedFlowersWeedsManure

Sources of carbon and nitrogen.

These are just suggestions, you can use whatever you have available without a problem as long as you respect the 50/50 ratio. Have in mind that the microorganisms need carbon to obtain energy and need nitrogen to decompose and reproduce so you should always have brown matter in your compost bin.

What not to compost?

  • You should not compost meat, fish, or bones, there are other techniques (bokashi) that focus on decomposing these things but in this composting setup, it will attract bugs.
  • Avoid composting diseased plants, diseases like the tobacco mosaic virus can stay in the soil, infecting all the plants you’ll be using your compost with.
  • Never use cat or dog feces.
  • Citrics can be bad for the microorganisms so avoid composting lemon, tangerine, or oranges. 


Composting: what not to compost

There are other methods of composting (like Bokashi) if you wish to compost meat, fish, and bones.

5. How to use my compost?

Your compost can be mixed with soil but the amount will depend on how long you let it decompose, you can use it as soon as you hit the 30-day mark but letting it go for longer will result in a higher concentration of nutrients which will result in needing less compost per plant.


Composting: how to use compost

You can use compost by itself or make your own soil mix, depending on how strong it is.

You don’t have to worry about it burning your plants so the amount you mix with soil depends on how long your cannabis plants take from seed to harvest, as a guideline you can mix 50% compost with 50% soil and add more if you think it’s needed, remember that compost works as a slow-release fertilizer so you can safely add it throughout your plant’s growth if needed.

If you've left your compost for a long time and it's strong, you can mix 1 part compost with 4 parts soil, for example, if you're mixing 1k of soil it should be 800g of soil with 200g of compost.


6. In conclusion

Composting is a cheap and effective way to feed your plants, because you can make it however you want it you can tailor fit it to your needs and the best part is you can do it with cheap leftovers found in every household. If you know more about composting please leave us a comment below!


External References:

1. Compost and Compost Tea Microbiology: The “-Omics” Era - St. Martin, Chaney & Rouse-Miller, Judy & Thomas, Gem & Vilpigue, Piterson. (2020).

2. Composting parameters and compost quality: a literature review - Azim, K & Soudi, Brahim & Boukhari, S & Périssol, Claude & Roussos, S & Thami-Alami, Imane. (2020).

17 August 2020