There are many reasons for creating your own soil mix for your cannabis plants, rather than using soil brought from the store. These include environmental concerns, cost, practicalities and horticultural preferences based on experience.
One of the easiest ways to reduce the environmental impact of cannabis growing is to mix your own organic soil. As well as being kind to the planet, mixing your own cannabis soil should ensure that your plants have all the nutrients they need for their life cycle right from the start, with minimum need for extra input later. Creating your own soil mix also enables you to experiment and gain confidence in managing the nutrients your plants will need. There is a real gift in getting your hands as dirty as possible – you will learn a lot. Although it requires more time and physical labour than going to the store, the rewards are many.
Good quality soil is rich in macro and micronutrients which means that you won’t need to use as many additional nutrient inputs or chemical fertilisers. This also means you shouldn’t need to flush your plants prior to harvest. Cannabis grown without chemical nutrients provides a tastier natural flavour which many people prefer. It also avoids the environmentally damaging impact of chemical run off associated with certain feeds and fertilisers.
If you are collecting soil locally its far cheaper than bought soil. In fact most of it can be free if you are resourceful. It’s just a case of looking around to find out what is available as close to home as possible.
Many premixed soils contain ingredients that are either directly harmful to the environment or whose extraction is energy intensive and/or damaging to the environment. For example, the harvesting of peat moss requires the draining of peatlands – fragile and valuable ecosystems that are home to wildlife and a diversity of plant life. They are also significant carbon sinks, which when drained result in the release of large quantities of CO2 back into the atmosphere. In addition, many companies that sell premixed soils and soil nutrients are also involved in environmentally damaging industries such as the sale of GMOs and harmful pesticides and herbicides. Finally, premixed soil comes in plastic sacks and is often transported large distances around the world before it arrives at your door.
Making your own soil mix
As you will know, if you have read my previous blog posts, I like to grow organic cannabis. It makes me feel better about what I am putting in my body and the impact I am having on the environment around me. Living in Jamaica with plenty of space to grow cannabis outdoors, I have been able to do this and experiment with different methods. So, I am going to share my tips for creating a local, organic and sustainable soil mix.
Besides water and sunshine, cannabis needs 3 main macronutrients: Nitrogen (N), Phosphorous (P) and Potassium (K). Micronutrients also play a role in keeping plants healthy and productive. These include calcium, iron, sulphur, zinc, boron, manganese and copper which occur naturally in things like molasses, kelp, bat guano and worm castings. In order to absorb these nutrients, the cannabis plant needs healthy and robust roots. The health of the root system can be supported by adequately aerated soil with good drainage and sufficient nutrients.
Step 1 – Choose your base soil
Try and collect top soil from 3 or 4 different local sites to ensure a good variation of soil types and hopefully a wider range of micronutrients. A good sign of a healthy living soil is the presence of earthworms. Making your own compost can help create more worms and you can also build a wormery to make your own worm castings. Avoid clay and dense soil as it is very important to get air to the roots. Scrape off the top inch of dirt and bag it up. Spread it out on a large tarp or concrete area and turn it all over to mix well, or put it in a mixer.
Step 2 – Aerate you soil
Collect some river or granite sand and crushed rock. Whatever local material you can find near you for free. Add to the soil alongside coconut coir to help improve aeration, maintain moisture and provide nutrients to the soil. I use coconut coir dust that I can collect from the coconut factories nearby.
Step 3 – Enrich the soil
Collect and add the following to your soil:
- Animal manure – I use chicken and cow manure because its readily available
- Compost – ideally you will have created your own garden compost
- Wood ash (provides potassium and phosphorus but can affect pH of soil so monitor carefully)
- Bat guano (I only use this as a top dressing as the plants switch to flower)
- Molasses is a great input for improving the health of your soil as this provides food for the healthy microbes in the soil. The greater amount of microbial activity in the soil, the healthier your plants will be. Molasses can be added to water and sprayed on plant leaves or poured onto the soil. I use it at 1 tablespoon per gallon.
Ratios should be approximately 50% top soil, 30% coconut coir and 20% manure, compost and ash. Layer everything and turn it over well to ensure it is thoroughly mixed. Please be aware that this soil is very rich in nutrients and is therefore not suitable for germination and seedlings.