Why Living Soil?

Organic cannabis hits different.

When properly grown and cured, the complexity of flavor and effect is hard to beat.

This aesthetic difference can be attributed to the diversity of nutrients and probiotics available in living soils.

Nutrient diversity fuels the biosynthesis of complex compounds like terpenes and flavonoids that contribute to cannabis quality.

Growing organic cannabis is not rocket science, but there is some science involved.

The basics of growing in living soils is the same if you are growing five plants or five acres.

If you invest a bit of time to better understand what is happening in the root zone, your quality and yields will improve.

Growing in organic soil is also a cost-effective way to cultivate distinctive cannabis at commercial scale in a market flooded with mediocre weed.

Consumers might not appreciate the complexities of cultivation systems, but they vote with their dollars, and organic herb is in high demand.

Root Exudates

During photosynthesis, plants absorb carbon dioxide, and make carbohydrates.

Up to 40% of this energy is shared with soil microbes as root exudates. These carbon rich exudates are composed of simple sugars, and organic and amino acids.

Most microorganisms don’t have access to atmospheric carbon and provide plants with nutrients and other benefits in exchange for this valuable energy source.

Plants can influence soil PH and share exudates selectively with the microbial communities that provide for their needs.

Learn more about Root Exudates in this peer reviewed paper.

Roots, soil, and microbes create a densely populated habitat known as the rhizosphere.

Soil Food Web

The soil food web is composed of interconnected kingdoms of life that cooperate, compete, and consume each other.

• Bacteria- These single celled organisms are abundant in healthy soils, and populations can double every 15 minutes.

• Fungi- Fungi form hyphal networks which enable nutrient transport within the soil and communication between plants.

• Nematodes- Nematodes are microscopic worms, many of which feed on plant roots.

• Protozoa- Protozoa are microbes that swim through soil water, feeding on bacteria.

• Worms- earthworms consume decaying materials and inoculate them with beneficial gut bacteria.

• Insects- Many insects spend part of their lifecycle in the soil. Some of these are detritivores, and consume decaying materials, others are herbivores and can emerge from the soil to feed on your plants.

Soil chemistry can also contribute to pest suppression. Nutrients like Silicon and Chitosan strengthen cell walls and aid chemical defense.

Cannabis Nutrients

Cannabis is a heavy feeder and is often cultivated in controlled environments.

The economics of these growing conditions favor high planting densities, and short crop cycles.

In addition to the initial nutrient charge provided by living soil, supplemental feedings during crop development can improve plant performance, and enables use of lower soil volumes.

Slow-release organic nutrients can be supplied by compost and dry amendments.

Liquid or soluble nutrients can also be fed during periods of rapid crop growth.

Liquid Nutrients

Fish hydrosolate fertilizers are great sources for amino acids and beneficial bacteria. Plants make amino acids from Nitrogen, but they can also uptake them directly from the soil and save the energy.

Soluble organic nutrients are usually micronized to increase surface area and can be suspended in a liquid solution.

Organic fertilizers should never be fed through irrigation systems or biofilm will accumulate and ruin your day.

Soil Amendments

Dry inputs are usually incorporated into soil mixes or applied early in the crop cycle to provide sustained fertility.

Protein meals are organic amendments with a high nutrient density.  These products have been dried and milled to increase their bioavailability and storage life.

Mineral inputs are mined from natural deposits. Some of these inputs require a long time to mineralize and are better incorporated into organic mixes prior to planting.

Dry amendments can be blended to make slow-release fertilizers with specific nutrient ratios based on crop needs.

Mineralization of dry inputs requires water availability.

Fertilizer spikes can be applied by opening the soil profile with a knife and inserting dry blends for contact with soil water.

Nutrient amendments can also be top dressed on the soil surface. Mulch application and surface irrigation provide water for mineralization.

Compost should be pleasant smelling. Foul smells indicate that bad actors are off gassing nutrients into the environment rather than keeping them in the soil.

Organic Chemistry

Chemical elements are the basic building blocks of all matter. (Remember the periodic table?) Some of these elements are nutrients required by plants and other organisms for energy and growth.

Cations are elements which maintain a positive charge due to their ratio of protons to electrons. Many plant nutrients are available as cations including Calcium (Ca++) Potassium (K+), and Nitrogen (NH4+).

Positively charged cations bond with negatively charged soil at cation exchange sites.

Phosphorous (PO43-), Sulfur (SO42-) and Nitrogen (NO3-) are available as anions. Anions tend to be mobile, and easily leached from soils as their negative charge prevents storage on cation exchange sites.

Soil PH

Soil pH is a measure of the potential of Hydrogen in the soil water.

This determines the acidity or alkalinity of the soil and availability of nutrients.

Cations like Calcium are basic, and will raise the soil PH, while Anions are acid forming and will lower soil PH.

Slightly acidic soils in the PH range of 6-6.5 are ideal for cannabis cultivation.

When growing with synthetic fertilizers it is important to adjust the PH of inputs. This is unnecessary when growing in living soils.

Liming agents containing Calcium ions are integrated into organic soil mixes to form bicarbonates which stabilize PH at a range of 6-6.5.

This buffer allows the plant to steer the soil PH as required for nutrient availability.

Organic N-P-K

Nitrogen is abundant as an atmospheric gas and is converted to plant available nitrates through decomposition of organic matter.

Nitrogen is required for the formation of amino acids, which are critical components of cells.

Phosphorous is a mineral element that is made plant available by phosphate solubilizing microbes.

Phosphorous benefits root development and fruit set. It serves as a storehouse of cellular energy and is a structural component of DNA.

Potassium enters the soil through application of minerals like Langbeinite, and from breakdown of organic materials.

Potassium has important functions in plant metabolism and stress adaptations.

Essential Nutrients

In addition to N-P-K, there are several other soil nutrients that are required in abundance.

• Calcium ions are critical for flower set and PH regulation.

• Magnesium is the central atom in the chlorophyll molecule.

• Silicon is a primary ingredient in cell walls and aids in plant defense.

• Sulfur is a building block for terpenes and other volatile compounds.

Micronutrients

Plants require trace amounts of many elements for optimal growth.

Mined products like greensand, basalt, and glacial rock dust contain a diversity of trace elements but can be slow to mineralize.

Some plants hyper accumulate trace elements from the environment.

Alfalfa and Kelp meals can provide a diversity of accumulated micronutrients when used as soil inputs.

Cannabis is also a hyper accumulator. This can be problematic as some trace elements are heavy metals that can cause compliance and health concerns in cannabis crops.

Silicon availability can limit uptake of heavy metals in many plants. This excellent academic overview is worth a read.

Irrigation water with high levels of dissolved oxygen (DO) fuels aerobic microbial activity.

Water should be kept between 60 and 70 degrees and commercial growers will benefit from super-oxygenating their irrigation water with nanobubble generation.

Container design, mulch application, and irrigation practices promote soil fertility and protect feeder roots which proliferate in interface conditions.

Soil Porosity

Water infiltration and air exchange are enabled by pores of various sizes within the soil matrix.

Soil porosity is the percentage of soil volume that is made up of these pores. Air filled porosity is the percentage of air that remains in the soil when it is saturated.

Pore characteristics are largely determined by the size and organization of aggregates and fibers in the soil.

Pore size regulates access of soil organisms to one another and to their resources.

Bacteria find refuge in micropores as protozoa and nematodes transit between linked macropores grazing on their brethren.

Soil Structure

Naturally occurring mineral soils are primarily composed of sand, silt, and clay.

These are aggregates of different sizes that determine the physical soil features.

Clay particles are very fine with minimal pore space for water or air percolation. These negatively charged colloids will clump together to form aggregates when positively charged calcium cations are present.

Potting soils are based on fibrous grow media. Peat Moss requires access to free calcium to neutralize its natural acidity, and Coco coir will uptake Magnesium and exchange it for Potassium.

Microbial activity in the soil results in mucilage, or biofilm secretion. This slime contains plant available nutrients, and glues soil particles together to form larger aggregates, improving the soil tilth.

Soil Organic Matter

Fertile living soils contain lots of Humic and Fulvic acids.

These organic acids are nutrient chelators that combine with trace elements to make them easily absorbed by plants.

Once the trace element has been absorbed, humic acids are returned to the soil solution to chelate other minerals.

Nutrient Uptake

Nutrient uptake is enabled by chemical, biological, and environmental conditions.

In favorable environmental conditions, microbes will consume mineral and organic inputs, and expel them in reduced form. Diverse communities create a chain of decomposition that results in the production of plant nutrients.

As nutrient compounds are mineralized, and enter the soil water, they become available for transport into the plant.

Root Structure

A roots growing tip is protected by a root cap which continually sheds and is replaced as the root penetrates abrasive soils.

The root cap secretes mucilage which lubricates the root path, aiding nutrient acquisition and soil structure.

As a root grows, radial roots will begin to develop along its length in response to hormone signaling from the root tip.

Container design has a big influence on root development.

Root pruning pots guide root tips to holes in the pot which stops their growth. This causes radial roots to rapidly develop, and initiate more radial roots, until the soil is colonized with a fibrous root mass.

Root hairs are extensions of epidermal cells that develop along each root to increase surface area for water and nutrient uptake.

Nutrient Mobility

Nutrients move into roots in a few different ways:

• Most nutrients move into plants passively, through mass flow, when soil water is absorbed for transpiration.

• Some nutrients can move from areas of higher concentration in soil solution to areas of lower concentration at the root surface through diffusion.

• Colloids containing nutrients can also be absorbed directly through root interception as the root pushes through the soil.

As nutrients move into roots from the soil solution, they are replenished by cations stored on soil exchange sites.

Phosphorous anions are not very mobile in soils, and plants rely on mycorrhizae to enable long distance transport of this element.

In natural ecosystems, fungal hyphae form a network that enables communication and resource sharing among plants and other organisms.

Most fertile living soils have indigenous mycorrhizal populations and inoculation with branded products is unnecessary.

Organic Cannabis

Organic cannabis cultivation can be as simple or as sophisticated as you want to make it.

If you are growing a few plants at home, start with a big pot of living soil, and you will probably end up with some decent weed.

Craft scale farmers will benefit from making their own organic soils, and growing connoisseur quality cannabis.

For commercial growers, large soil volumes provide a buffer which resists rapid change and helps to minimize errors.

Living soil is at the heart of sustainable farming systems.

Polyculture

There are good reasons to grow in living soil other than plant health and flower quality.

Indoor cannabis cultivation consumes far more energy per gram than any other crop on the planet.

Sustainable growers take a polyculture approach to cultivation where different plant species share resources and manage pests.

• Marigold is a great companion plant which suppresses nematodes and other root pests.

• Garlic is a good rotation crop and scavenges Sulfur for the cannabis plants that follow.

• Legumes fix Nitrogen in the soil when used as a cover crop during the off season.

There is a lot more to sustainable growing than polyculture and living soil.

• Organic waste is recycled into valuable nutrients with on-farm composting systems.

• Indigenous microbes like Lactic Acid Bacteria (LAB) are collected on site and cultured to increase soil fertility.

• No-till systems cycle nutrients into the soil while preserving fungal networks and earthworm tunnels.

This article is almost over, and I feel like I have barely scratched the surface.

(Sorry for the No-Till joke.)

Greenhouse growing

Cultivating organic cannabis in greenhouses with supplemental lighting enables year-round production of high-quality weed.

Recent research has demonstrated that some entomopathogenic (insect killing) fungi also form mycorrhizal associations with plant roots.

This means that after the fungi digest a pest, they share the food with your plant.

By the time you see a nutrient deficiency, it is too late to correct course, so cultivators rely on analytical tools to design and manage organic fertility.

Laboratory analysis of soil samples provides insight into the chemical profile of the soil.

The ratios between elements are more indicative of soil fertility than their actual values, which vary between labs.

Leaf tissue analysis provides insight into nutrients that have been absorbed by the plant.

Comparison of soil and tissue nutrients enables us to fine tune our fertility systems to keep up with aggressive growing environments.

Get the Book

I really appreciate you sticking with me to the end of this very long article.

In fact, I have decided to write a short book about organic cannabis cultivation. I am going to try to include everything you might want to know about making organic soil and growing amazing cannabis.

Since you are still reading, I assume that you are a soil geek like me and will probably like this book. If you want early access, fill out the form below, and I will let you know when I hit publish.

Happy Growing!