The Dirt On Growing Green: What’s This Organic Matter?

By Sunny Kaercher

Perhaps one of the most prolific, and misused, words of the past decade, organic, appears as if it is here to stay.  This article is not about organic cultivation methodologies — or even any certifying body that might confirm that regulate it —  but rather, organic matter in the soil (and/or “grow media”). Organic is the backbone of growing hearty plants naturally, and the key to understanding nutrient cycling.

If you aren’t cultivating via aeroponics or the variety of hydroponic mediums like rockwool, hydroton or lava rock, then you are growing in some form of organic material, and this article is relevant to your operation.

Organic matter is decomposed organic material. And what is an organic material? Essentially, anything carbon-based qualifies as an organic material. A few of our favorite sources for organic material are leaves, grasses, kitchen scraps (aside from animal products & oils), manure, woody materials and root balls. Though they are all carbon-based, each has a unique amount of Nitrogen within their composition. Measured as the C:N ratio (carbon to nitrogen), materials can casually be categorized as either “green waste” (nitrogen-rich) or “brown waste” (carbon-rich).  Anyone who composts probably knows that you want a specific balance of green to brown waste to build rich organic matter. The process of decomposition is beautiful and complex. A fleet of microbes, primarily bacteria and fungi, can take credit for the break down.

Soil microbes consume carbon for energy, and nitrogen for protein (building blocks). As they consume materials, they have the ability of converting it to plant-available nutrients – either in their waste or immobilized in their bodies. Organic matter is valuable as more than just a nutrient source. It has a high water-holding capacity, resists compaction, and encourages aggregation of particles. All of these characteristics benefit both microbes and plant roots.

Referring back to the first Dirt on Growing Green, a native soil comprises of approximately 5% organic matter. However, the soilless medias that are exceedingly popular in the cannabis industry (and traditional horticulture) have much more organic matter/material. Pumice, perlite, or any other rock-based component aside, they are entirely organic materials. Peat moss, coco coir, forest materials, compost, worm castings; they are all carbon-based. All of these materials should be stable (compost as a ‘humus’), meaning they have gone through the majority of the decomposition process. However, there is likely more to be done, and the break down will resume as roots grow and soil microbes thrive. In other words: as your plant grows, nutrients will continue to become plant-available (mineralization).

So what’s the magic recipe of organic matter for growing cannabis? Well, it entirely depends on your situation. But regardless of your situation, if you are growing in organic material, you will want to replenish organic matter often. Either with fresh grow media, or top dressing to integrate the benefits. Top dressing can range from applying humic acids, to mulching, to spreading mature compost. Effectively, you are feeding the microbes so that they can feed the plants. Old leaves turning in to new leaves. What better demonstration of the interconnectedness of this world?

The Dirt On Growing Green: Soil Texture & Composition

By Sunny Kaercher

Every grower has their own approach to cannabis. Varying techniques and products are plentiful, but one thing that remains constant is that healthy plants depend on healthy roots. This is the beginning of a series dedicated to creating and maintaining a vigorous root zone, also known as the rhizosphere. These articles will range from horticultural to scientific, with the goal of educating cannabis growers about natural cycles and what makes the perfect organic growing media.

My name is Sunny Kaercher and I work with Miller Soils. We offer all-natural, cannabis-specific container media catered to growers that want to minimize their inputs and see big, beautiful yields. We design our medias to mimic and support ecological balance, both within the container and out. Now, let’s dig in.

This being the opening piece in The Dirt on Growing Green, it seems appropriate to cover some of the basics of soil science.

One of the first things to understand is soil composition; what’s in your dirt?

45% of soil is composed of mineral particles, which originate from the parent material several horizons below the surface of the earth. These particles, sand, silt and clay, are measured and identified by their diameter. Together, their ratio determines soil texture, which greatly affects important soil properties. Sand, the biggest of the three (.05-2mm), is great for drainage, but has a very low holding capacity. Clay, on the other end of the spectrum (less than .002mm), has a high surface area for adsorption of water and nutrients. Though this retention is cornerstone to a thriving rhizosphere, too much clay leads to compaction, meaning inadequate drainage and roots that cannot breath. A balanced soil, called loam, will have all sizes of particles, and in turn embody all characteristics.

Another 5% of soil is composed of organic matter (including roots) and soil organisms. These I will tackle another day… but what about the remaining 50%?

The remaining half of soil is a delicate flux of air and water, existing in the pore spaces between the physical substrate and active biology. This pore space, though ‘empty,’ is incredibly important to the success of any plant. Unlike leaves, plant roots breath in oxygen (O2) and respire carbon dioxide (CO2). Soil microorganisms and fauna need porosity for this same reason. Soil must allow gas exchange with the greater atmosphere. Water also moves through these pore spaces, but it is infinitely more complicated. There are 3 types of soil water, gravitational, capillary and hygroscopic. The latter is adhered so tightly to particle surfaces, plant roots cannot absorb it. Gravitational water drains from the soil in a matter of days, whereas capillary will be available for longer. This is directly tied to pore size and porosity. It is critical to understand soil water behavior in your cannabis container, whatever it may be, because it affects everything else, from pH to watering/feeding schedule to root vigor.

Now that we’ve covered the foundation of life in soil, air and water, we can move on to the food web.

Stay tuned for next time!