Let's Talk Dirt-y: Creating your own soil mixes

Last week, Golden Hills hosted a program at Iowa Western Community College about creating your own soil mixes.

Nick Bonham with Lucky Toad Restorative Gardens taught the class, which included a classroom portion followed by mixing the ingredients in the greenhouse.  

The following info is from Nick Bonham with Lucky Toad Restorative Gardens:

Soil is a composite of organic matter, clay, and rock particles, the nature of which varies between climactic and geographic regions. It is an incredibly dynamic environment (about which we know surprisingly little) and provides a home to plants, fungi, animals, and microbes. It is the driving engine for life on earth.

When cultivating plants in a greenhouse, we aren’t using “soil” per se, but rather a growing medium that simulates its necessary attributes while minimizing risk. Different plants have unique adaptations and therefore specific requirements of their growing medium. For example, cacti have evolved expansive, shallow root systems and require soil with rapid drainage. Such factors are crucial when determining the proper growing medium for your plants.

This class focused on a general purpose “nursery” mix, one that is especially conducive to starting seeds and raising plants though the early stages of life before installation.
 
Like animals, plants require a varied diet of macro- and micronutrients to truly thrive. Before we get into the composition of the mix, let’s review some basic soil chemistry:
 
-Nitrogen is a key component not only of protein synthesis, but chlorophyll production as well. It is fixed into the soil by microorganisms. All plants need it, but certain crops like corn are especially ravenous for this nutrient.
 
-Phosphorous helps with plant metabolism (nutrient acquisition/ transportation) and energy production. Deficiency usually appears as stunted, dark green foliage.
 
-Potassium is a key factor in moderating water, carbohydrates, and nutrient transportation and has been attributed to cold-hardiness. It also facilitates enzymatic processes.
 
These three comprise the NPK portion of fertilizers, and their respective ratios can be inferred as such. While these comprise the “macro” or primary nutritional requirements of plants, there are several others worth mentioning:
 
-Sulfur helps maintain cellular health and proper DNA synthesis. Over-watering particularly leaches sulfur. Affected plants will display new growth that is yellow/yellow-green.
 
-Calcium assists with cell division and maintenance of structure. Woody plants contain 10x the amount of calcium as non-woody plants. Deficiency results in stunted new growth, often with brown spots that begin at margins and spread to the interior.
 
-Magnesium is a component of chlorophyll and helps fortify the cell wall. Deficiency displayed in older leaves with dark green veins but yellow to pale green foliage. Magnesium sulfate (non-scented Epsom salt) is a wonderful occasional treat for plants, and an incredibly effective shock reducer while transplanting.
 
Now that we know what plants crave in soil, we can create a successful facsimile using ingredients from a garden supply store. The following recipe is one I have used for years to great effect, and the contents are as follows:

Structural Medium
-Coco coir (3.5 cubic feet, sifted)--- Preferable to Peat Moss, details in discussion
-Vermiculite, coarse grade A3 (equal by volume to coco coir)----Preferable to Perlite, details in discussion
-Worm Castings (30 lb, sifted)

Nutrient Profile
-Blood meal (  3 C )
-Bone Meal ( 3 C  )
-Kelp Meal ( 3 C  )
-Azomite (1.5 C )
-Mycorrhiza (2 Tbsp)
 
When combined, these ingredients create a mix that is not only properly nutrified but facilitates root growth and minimizes the risks of disease. By retaining water well but draining and drying at an advantageous rate, risks of fungus and root damage are minimized. The relative porosity of the mix facilitates oxygenation and rapid root movement. It is particularly well- suited to vegetables and many species of prairie plants, though I wouldn’t advise using it for hydroponics.

Nick discussed which types and brands of ingredients he used to provide which nutrients: 

Then demonstrated how to mix the ingredients together...

Once all the ingredients are mixed, you have a growing medium that will help germinating plants thrive! Lucky Toad Restorative Garden specializes in native plants, but this soil mix is also great for vegetables and other garden or farm crops. 

To find out about upcoming Golden Hills programs, visit goldenhillsrcd.org/events.