Published in Flex420, 2022

The interactions of organic matter and microbial life creates our soil biology. This biology is influenced by the ways in which we manage soil. When working with our soil, we are always seeking an equilibrium and balance within the microbial life and pH, so that our plants can thrive. Creating a synergy between the soil biology and the biology of the plant itself is the ultimate goal - this way the farmer can take a step back and let the system work for itself. For example, altering the pH of soil favors certain organisms - intending to support fungal decomposers rather than bacteria. Likewise, adding an easily decomposed carbon source will stimulate microbial growth. This growth will immobilize nutrients, which will be released once the carbon source is exhausted. Building and feeding the biology of the soil allows for the soil and plant to create a system that ultimately results in healthier and happier crops.

The microbial life within soil is dormant at any given moment. This means that it has potential and will react to various influences. Because of this potential, we are able to manipulate the biology through input and an understanding of the plants natural biological systems. 

Soil microbes improve the nutrition of plants, helping to regulate and digest the nutrients needed for the plant. This can also enhance plant resistance to pests and diseases. These beneficial soil microorganisms may affect harmful members of the soil community more directly through competition, parasitism, or other mechanisms. Living soil benefits both the plant and the farmer and creates a loop between the plant and microbes.

Combating pests and pathogens using soil biology

Various benign soil bacteria and non-pathogenic fungi can also “prime” the production of plants’ own natural defensive chemistry. This will allow a more rapid and vigorous response to attacks by pathogenic bacteria, fungi and/or viruses. Depending on the species involved, this ‘induced systemic resistance’ (ISR) may induce plant defense against soil pathogens and some foliar pathogens and insects. 

The plant influences the environment around its roots. Anywhere from 10-40% of the carbon that is fixed by a plant through photosynthesis will be released as both organic and inorganic forms. The chemical, biological and physical processes in the rhizosphere will be the most influenced by the organic forms. Encouraging both the plant’s natural defense biology, and a diverse microbial population will help to fight pests from all angles. For example Trichoderma species produce a wide range of antibiotic substances and are capable of both out-competing certain soil pathogens and parasitizing others.

How to build your own beneficial biology within your soil 

If you want to add a lot of nutrients and you have the time, build your own living soil. This means adding a diverse array of organic nutrient sources. Inoculating with a good, quality compost and some beneficial mycelium. Try not to overthink it, because once the nutrients have biologically transformed, the plant won’t know what the source of the nutrient was and will tie up its favored subgroups. Mix the nutrients with energy sources, wood chips, corn or sorghum residues, or a coco coir. Then add in some biochar (look for a product derived from wood with more than 90%C), this mix will heat up - let it do so. Once it is cool, blend with your chosen substrates to create your final mix with room air space and water retention.

The final step is to tune the pH. This can be measured using a slurry test, with the final pH adjusted to 6-6.5. Add dolomitic lime if you need to raise pH. Allow the pH to equilibrate for about 4 or 5 days and then re-measure. If you need to lower pH, use raw peat. This has a pH of around 4. The pH can be measured immediately after addition. Check EC in a stirred slurry, an EC around 4 is alright, but try not to go higher than 7. If EC is too high, simply dilute the blend, don’t try and wash it out. A balanced pH helps the plant’s biology and the microbial population to thrive.

Even with the most advanced microbial techniques it is challenging to characterize these microorganisms - let alone understand what they are contributing to the function of soil at any moment. There is so much diversity existing within the soil and it has massive potential, the key is harnessing this potential. When making soil, there is no real way to pinpoint which microbe is the one that counts the most. This means that the goal should always be to bring in as diverse a population as possible. The more diverse our soil biology, the more resilient our plants will be and the higher quality our cannabis will be.