Soil biology is a key component of healthy cannabis cultivation. It is critical to understand how it works and how to optimize it.
Cannabis growers can benefit from understanding how their soil bacteria and fungi influence their plants. Whether in a controlled environment or outdoor production, cultivators can make their soils more conducive to biological life.
1. Soil Aggregation
Soil aggregates are tiny particles that bind together and form complex pore spaces that control the movement of air, water, nutrients, and microorganisms in soil. They are a key component of the complex symbiotic relationship between plant roots and soil biota.
The stability of soil aggregates is a critical aspect of soil function and fertility. Unstable aggregates disintegrate during rainstorms, promoting erosion.
Aggregate stability is also an indicator of the microbial activity and nutrient cycling in soils. When the proportion of stable aggregates increases, soil quality generally improves.
Various physical and biological factors influence soil aggregate formation, including particle size distributions, microbial decomposition of organic matter, soil chemistry, and weathering processes. Specifically, clay soils form aggregates quickly because their small particles have electrically charged surfaces.
Nonclay soils are slower to form aggregates. They need the addition of charged organic matter to glue particles together.
Soil texture also affects soil aggregate stability. Silt loam soils have smaller particles with no electrical charge and are more prone to disintegration by wind or water erosion.
A variety of dry soil amendments, such as perlite and vermiculite, can be added to cannabis cultivation growing media to increase aggregate stability. These dry additives are a popular choice for hydroponic growers, because they improve drainage and aeration in the growing medium.
Stable aggregates are important for infiltration and root growth, resistance to water and wind erosion, and the ability of cannabis plants to resist disease. They also help maintain the nutrient balance in the soil, a critical factor for healthy cannabis crops.
2. Soil Fungi
Understanding the role of soil biology in cannabis cultivation is a key factor in sustaining yields and preventing crop disease. In particular, fungi play a critical role in this process.
Fungi are microscopic, plant-like organisms that can be single celled or grow in long threadlike structures or hyphae that make a mass called mycelium (figure 1). Some fungi have symbiotic relationships with living plants. These beneficial fungi are often called mycorrhizal fungi.
These fungi live in the soil and in plant roots. They form a symbiotic relationship that helps the plant absorb nutrients and water from the fungi. The fungi coat their hyphae with a compound called glomalin which serves as a protective coating that prevents nutrient and water loss while also serving as a soil glue.
Soil fungi are a key component in soil nutrient cycling because they break down organic matter to release useful nutrients for plants. These nutrients include C, N and P.
A succession of fungi species will colonise dead organic material in the soil, based on their ability to break down different components of organic matter. The most important fungi will break down lignocellulosic materials like cellulose and lignin.
The ability of these fungi to decompose tougher sources of organic matter means that soils can have higher levels of nutrient availability. This is particularly helpful for soils that have been impacted by agricultural practices such as fertilizer, insecticide or herbicide use.
Fungi are a major contributor to the diversity of soil microorganisms and their abundance can vary from place to place. This diversity helps improve the function of the soil ecosystem and can be a strong indicator of environmental conditions.
3. Soil Microorganisms
A key factor in the soil’s health is its microbiome, which consists of many types of bacteria and fungi that live in the soil on or within plant roots. These organisms are a crucial component in the biogeochemical cycles that transform the carbon-to-nitrogen ratio (C:N) of organic residues into humus and nutrients.
The amount, type, and availability of SOM in the soil determines the microbial population, which evolves rapidly. Some of the initial decomposers (bacteria) eat easily digested sugars and proteins; others consume more resistant SOM. They then release nitrogen to the soil, which becomes available to other microbes or absorbed by plants.
Soil microorganisms are also involved in other soil functions, such as element circulation and mineralization of organic matter. They play a role in nutrient release to plants, including the release of essential amino acids and nucleic acid bases. They are also important for rhizosphere microorganisms, which help increase plant health and protect them from pathogens.
In addition, the microbiome is influenced by climate, as microbial populations are sensitive to even small changes in temperature and humidity. Cannabis plants that are cultivated indoors are especially vulnerable to these factors, as air circulation is necessary for healthy growth and the ability to withstand fluctuating temperatures.
The microbial activity in the soil is a determining factor in the production of a high-quality cannabis crop. This includes enzyme activity, which is an indication of soil metabolism and the potential for the formation of humus, molecular nitrogen fixation, nitrification and denitrification, and phosphorus forms transformations or detoxification. Enzymes are also involved in nutrient release to plants, including amino acids and nucleic acid bases.
4. Plant Roots
The roots are the primary point of contact between a plant and soil, absorbing nutrients from the growing substrate and delivering them to the rest of the plant. They are the most important organ in the plant’s nutrient and water uptake network and can greatly affect the quality of your cannabis product.
Roots also have a great influence on the microbial life in the zone of soil immediately adjacent to them. This area is called the rhizosphere and can be as much as two to ten times larger than the surrounding soil.
In addition to promoting microbial life, plant roots help to improve drainage and nutrient supply for the growing plant. This is because the rhizosphere acts as a sponge, soaking up excess water and nutrients from the soil below them.
Likewise, some soil bacteria form symbiotic relationships with plants to increase their availability of nutrients. For example, rhizobium bacteria infect root hairs of legume plants and fix atmospheric nitrogen into plant-available forms. This nitrogen is then released once the plants die, allowing future crops to take advantage of the excess.
Another way that plant roots positively impact microbial life is through their interaction with beneficial fungi. These fungi, such as Trichoderma and endomycorrhiza, can form symbiotic relationships with the capillary roots of a plant, forming a nutrient uptake network that is easier for the plant to access than without them.
These fungi are especially beneficial for growers who use organic fertilizers, since they make the nutrients easier for the roots to absorb. In addition, they can help the roots combat fungal problems such as pythium and fusarium. This, in turn, helps the roots develop strong, healthy growth and vigor that allows for more vigorous flowering.
5. Plant Nutrients
Plant nutrients, such as nitrogen, phosphorus, potassium and other minerals, are essential for healthy growth. These are transported through the roots to the conducting tissues, xylem and phloem, where they can be used by plants. The structure of the root also determines how quickly these nutrients are absorbed.
The soil contains a variety of organisms, including bacteria, fungi and protozoa. These microorganisms play a vital role in nutrient cycling and decomposition, as well as helping to suppress plant pathogens.
These bacteria are also able to fix atmospheric nitrogen into an organic form that can be used by plants. Nitrogen is important for the growth of many plants, and a lack of this nutrient can cause some varieties to fail.
Similarly, potassium is important for the growth of some species, and a shortage of this mineral can cause some to fail. Potassium is also known to have antifungal properties, preventing certain kinds of fungi from growing in the soil.
Finally, the earthworm is an important nutrient-transfer agent in the soil. These microscopic creatures break down and release organic matter into the soil, which helps to aerate it and improve its water-holding capacity.
In addition, they also excrete wastes that contain nutrients, such as nitrogen, phosphorus and potassium. These wastes are a source of natural fertilizer that can help cannabis plants thrive.
The environmental impacts of cannabis cultivation can vary by production system. Indoor and mixed-light systems have a lower impact on ecosystems than outdoor farms, but they still may require more external inputs such as energy and fertilizer. Likewise, large-scale cultivation facilities have a higher negative impact on landscapes than smaller farms. However, this may be mitigated by implementing sustainable cultivation practices and by developing better siting, management and air pollution controls.
