The Dirt On Growing Green: Soil Texture & Composition

The dirt on green

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!

Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>