At the Soil and Compost Workshop with Keoki Moore at Shared Harvest Community Garden we learned how the fertility of the soil throughout the history of Earth has been perpetuated by decomposing biological matter and how we can recreate that cycle to improve our gardens' soil fertility through composting.
"Gardening is about the soil", Keoki told us right off the bat, and "soil is about the microbes".
Without healthy soil we won't have healthy plants. And without healthy soil microbes we won't have healthy soil.
4 Components of Healthy Soil
- Air/pore space 25%
- Water 25%
- Organic Matter 5%
- Minerals 45%
Most of soil is actually just space! Whether its oxygen in spaces between the solid material or water, that space is essential to plants thriving. Which is why stepping on your soil, which compacts those pore spaces, is strongly discouraged.
Note: We use the word "organic" in many ways. To a chemist, "organic" means anything made of carbon (but anything made from carbon should not necessarily be put into our soil). "Organic" food is used to mean food that is grown using organic practices such as avoiding synthetic fertilizers and pesticides. For us in the garden, organic matter simply means matter that came from living organisms (ex. leaves, manure, coffee grounds). For clarity Keoki referred to is as "biological material."
2 Elements of Healthy Soil
Temperature is important because we won't be growing any veggies while the ground is still frozen and as temperature rises the rate of biological activity increases meaning our plants will grow faster (to a point).
pH means "potential of hydrogen" present. On the pH scale 0=acidic (higher percent of hydrogen) and 14=alkaline (higher percent of hydroxide). Hydrogen and hydroxide are atoms/ions that influence the availability of minerals in the soil. In other words, soil pH is important because even if the minerals that plants need to grow are in the soil they may be bound up in such a way that plants can't use them. pH also affects the level at which soil microbes can proliferate. The ideal pH for gardening depends on the plant but plants generally grow in the 5.5 to 8 range.
Note: When your soil is deficient in a certain mineral that is affecting your plants simply adding an amendment of that mineral may not solve the issue as the soil pH may keep that mineral bound up in the soil. When dealing with a deficiency, your first remedy should be to add good compost (which will introduce microbes that can help unlock those minerals). After that, amendments may help.
How to measure soil pH:
- Litmus paper test (cheap, quick, though not 100% accurate its enough to get an idea)
- RapiTest electronic tester (immediate results) Has anyone used one of these? How well did it work?
- Lab testing (Accurate and usually with some helpful advice though more expensive and takes time) At OKCG we got our soil tested through CSU Soil Testing Lab which gave us pH and mineral content along with amendment suggestions. You can pick up a soil test kit at CSU Extension at the fairgrounds in Durango.)
Another piece of healthy soil is tilth, or the "workability" of soil, which is made up of texture and structure.
Texture- Size of grains that make of the soil (clay being the smallest and sand being the largest)
Structure- Arrangement of the particles
How do we influence tilth?
Irrigation - We have a tendency to overwater our vegetable gardens (yes, even in SW Colorado) which coagulates the soil particles leading to less air space and root rot. Soil should be moist but not dripping. Remember to go down 4-6 inches to test moisture.
Cultivation - Any process that rearranges soil, from using your fingers to a hand trowel to a tiller. Beware of tillers which can actually ruin your soil structure.
Amendments - Adding compost and humus can build god soil tilth.
So how about those bacteria we keep mentioning...
Healthy soil is alive! It is alive with not just worms, but also anthropods and microbes. To learn more about them Keoki pointed us in the direction of Soil Scientist Dr. Elaine Ingham, who coined the term "soil food web" to describe the complex interactions formed in our soil.
The microbes that live in our soil perform a multitude of things to help our plants from taking Nitrogen from the air and making it into a usable form for plants to breaking down dead plant and animal material to release the nutrients to be used by the plants.
How do we take care of our soil microbes?
Taking care of our soil microbes is essential to plant health. One of the ways we can do that is to create an environment those microbes will thrive in. They are just like us! They need food, water, air, and protection!
We feed them with biological material. That's were the compost comes in.
Compost - Decayed biological material, the final product being humus.
Humus - (pronounced hue-mus...not hummus!) Organic matter that has broken down as much as possible, it is made up of complex molecules called humic acids. Though much about humus remains a mystery, in soil it helps retain water and nutrients.
How to make compost:
Taken from The Garden Project of SW Colorado School Resource Guidebook
Activity 2.6 Building your own compost bin
Another way to use compost is by making a compost tea.
Check out the full instructions from Keoki!
Shared Harvest Community Garden started in 2002 near Durango on the private farm of Bob Kauer and Jama Crawford with 30 households, perhaps the first community garden in La Plata County. The garden covers one cultivated acre plus outbuildings and today serves 80 households, who each work 2 hours a week in cooperative teams to raise organic vegetables and berry crops. Despite its 7,000 elevation and short frost free season, the garden is frequently cited by agricultural experts as one of the most productive gardens in the mountain southwest. In 2012 Shared Harvest began to operate year round after constructing a large solar-powered greenhouse.
Contact: Jama Crawford, firstname.lastname@example.org
Compost Team Captain at Shared Harvest
"Keoki has transformed the garden,
Thanks Keoki for a wonderful workshop! Time for us to get going on our own compost pile!
And thanks to Bob and Jama Crawford for letting us come visit the flourishing community garden!
School of Earth and Environment - University of Western Australia
CSU Extension- CMG Garden Notes: The Living Soil
Organic Gardening Magazine - What is soil pH? (article)