Thank you Silvia for this wonderful summary of the “Secrets of Healthy Soil” Workshop! the original posting of this blog can be found here. Scroll to the bottom for pictures!
“If a healthy soil is full of death, it is also full of life: worms, fungi, microorganisms of all kinds … Given only the health of the soil, nothing that dies is dead for very long.” ~ Wendell Berry, The Unsettling of America, 1977
Well, I had ~ 20-25 people at the “Secrets of Healthy Soil” workshop last Wednesday and I feel happy and inspired to run more of these workshops…
It was great to have entire families and “children” from 3-70+ (really!) and really fun involving them on the experiments and tests about soil texture, soil structure, water infiltration and water/nutrient holding capacity of soil…I can surely say that everybody got their hands dirty!
These are a summary of the topics we covered and some links and resources for those who were there and for those who couldn’t attend but were there in spirit. Please note that each one of these topics may require a full course in itself, sometimes involving an entire scientific “leg”…my intention here is sharing the basic concepts which remain the same for all:
What is Soil?
Soil can be defined in many ways and may mean different things for a child, a farmer, a gardener or somebody living in an apartment.
But beyond us humans, soil is a living system: it is being constantly created by the combined action of climate, topography, parent material (mainly rocks), animals, plants, insects, fungi and all types of microorganisms as well as time…it may take up to 1,000 years to create 1 cm of topsoil!
The current status of soil
We have lost between 30-40% of our topsoil only in the last 100 years. While soil is constantly created, it takes thousands of years to “be” again so it is considered a non-renewable resource.
Our soil is only a thin layer on the top of the dry areas of the Earth, not all areas are covered by soil and not all soils are “arable”. Soil has been degraded and eroded by mismanagement and abuse and polluted with waste of all kinds.
With the expectation that humans will need to increase around 60% their food production by 2050, there is no much room to go…
What is “healthy” soil?
A healthy soil is a soil that can maintain biodiversity and life. This is not achievable by artificial inputs such as fertilizers and addition of minerals. Health is an ongoing process that Nature does very well, if we only support her in doing so.
Topsoil , urban soil and potting soil
Topsoil is what’s described here and in my workshop: it is created by natural factors through thousands of years. It cannot be artificially “created” but its structure and (as a result) its water and nutrients holding capacity, its porosity (which impact water and air circulation and root accessibility) as well as its compact-ability can all be improved by the steps described at the end of this post.
Urban soils are a mixture: most urban soils are no longer topsoil as they have been removed, mixed and replaced, sometimes with strange materials. For that reason they may have different “behaviours” and re usually contaminated.
Potting “soil” is not soil at all: it would be better call this a “growing media”. Even when organic, potting “soil” is manufactured to create the optimal growing media for plants. For this reason, do not expect to get the same results as in real soil: there is no life or interactions in potting soil as what you can find in real soil…but they are the best to utilize in containers, as regular soil will die and compact very fast if put in a container!
Soil texture and why it matters
Soil texture is the percentage-ratio of sand, silt and clay you have in your soil. This is usually a result of the interaction between parent material of the area where you live and the many other factors or “soil partners”. It usually cannot be changed, but the structure (which is in part a result of this mix) can be improved when you support living systems by adding organic matter and increasing soil life.
The type of soil (clay, silt or sand or a combination of those with diverse degree of each component, see triangle below) will impact things such as compactability and water/nutrient holding capacity:
- Clay = extreme compactability = poorair content
- Silt= moderate compactability = moderate air content
- Sand= poor compactabiity = excellent air content.
Water holding capacity…
- Clay = excellent(but with moderate plant availability)
- Silt = excellent(and excellent plant availability)
- Sand = poor
CEC (Cation Exchange Capacity: this is the ability to attract nutrients in the form of minerals)
- Sandand silt (Quarz= no electrical charge / nutrient neutral)
- Clay (Silicon and aluminum, some iron= positively charge / attracts and keeps nutrients)
You can test your soil texture using the Jar method (sedimentation) or the ribbon method (making a ball, a worm and a ribbon with your hands)
Soil structure and why it matters
Soil structure is how the soil particles are attached to each other: it influences how water and air will circulate because the soil aggregates may have smaller or bigger pores (holes) and the “matter” will be organized in different shapes too.
Soil structure can be seen under the microscope but for expert gardeners, farmers and horticulturist may be “seen” and “felt” right by looking at the way soil forms aggregates and how it behaves.
Soil biodiversity and why it matters
Soil contains 1/3 of all the biodiversity living in planet Earth: a spoon of soil can have hundreds, sometimes thousands of different species and millions of individuals…soil biodiversity is not only made of microorganisms: it also includes fungi, insects, worms and all kind of animals who live (even if temporarily) under the soil and on the top of it: it also includes plants of all types and their dead matter which is decomposed by all the other creatures.
The more diverse life in the soil is, the more health your soil has: because biodiversity is nature’s way to ensure that “important functions are covered by multiple elements”. As I call it, it is nature “backup” or “Plan B”.
Soil pH and why it matters
pH is the acidity or alkalinity of a substance. The scale runs from 0 to 14 and different substances in the world have different pH. A pH of 7 is neutral (such as water).
Soils may range from very acidic (4) to very alkaline (10). Parent material, rainfall and climate may affect soil pH. Most plants love a pH of around 6.5 with a range from 5.5 to 7.5 being OK.
Why is important? Because nutrients become available or unavailable to plants depending on the pH.
Getting the soil pH is easy: there are pH pens and also pH strips and other cheap tests kits being sold at nurseries. You can also anticipate the soil pH by looking at the types of plants (and weeds!) that thrive in your soil and the status of their leaves and general growth.
In order to change your soil pH you also need to know your soil texture, because more material may be needed to change the pH of clay (because of the positively charged clay particles)
You can then use limestone to raise pH level or sulfur to lower it.
Testing your soil
In general, you need to test your soil for texture, structure, pH and to see whether it has heavy metals or other pollutants:
- When you move to a new house/land
- When you start a new garden (more if you plan to grow food!)
- Every 2-3 years or when you change the type of crops you grow there
- When you suspect your soil is contaminated or polluted
Steps to increase, restore or maintain soil health
- The best you can do is try not to disturb the soil: it may sound crazy, but soil “repairs” itself if you are not always digging, tilling and adding stuff…and if you allow life to live there!
- Add organic matter: organic matter increases life diversity and improves structure, which in turn improves water-and-nutrient-holding capacity, permeability, etc.
- Keep the soil covered all the time: by mulching, rotation/succession/companion planting or with cover crops that you’ll turn into “green manure” and tea brews…
- Avoid compaction: build paths so you only compact certain areas of your garden when you garden or harvest, but allow soil in general to breathe and be free of “feet”. Select a different area for children and pet’s play and rotate farm animals.
- Water wisely: harvest rainwater, create channels, swales and ponds or bury terracotta containers so you don’t have to artificially irrigate and the water don’t flood or runoff when it rains: water can easily erode nutrients and change the structure f good soil
- Protect your soil and the life in it: increase biodiversity, don’t kill life: pesticides kill much more than the “pest” they are intended to kill, fertilizers have unexpected side effects and poor waste management contaminates the soil
FAO FAQ about soil and other resources: http://www.fao.org/soils-2015/faq/en/
Urban Garden, managing risks of contaminated soil: http://ehp.niehs.nih.gov/121-a326/
A guide to collecting soil samples: http://extension.oregonstate.edu/sorec/sites/default/files/ec628_a_guide_to_collecting_soil_samples_for_farms_and_gardens.pdf
OMRI Canada: organic product list: http://www.omri.org/omri-canada
USDA “Unlock the Soil” videos and info: http://www.nrcs.usda.gov/wps/portal/nrcs/main/national/soils/health/
What weeds are telling you about your soil: http://www.gardensall.com/your-weeds-are-telling-you-something-learn-to-interpret-them-here/
Look to the weeds: http://homestead.org/DianaBarker/LooktotheWeed/SoilIndicators.htm
Ray the soil guy videos (excellent!!!): https://vimeo.com/channels/raythesoilguy
~~~Special Thanks to:
Village Surrey Transition group and its core members for their support in promoting, finding a location and being there for me!
Friends of the Grove for promoting and having your amazing people so present and engaged!
City of Surrey for listing the workshop under the Environmental Extravaganza and providing the room at Newton Rec Centre
My wonderful Food for Thought Community Garden fellow gardeners for being there and supporting me
The amazing people of Surrey and specially, Newton! for showing up with your children and allowing me to share some of this with you…
The two little elfs who helped me carrying water, colouring the samples and doing all the experiments
Pictures: all pictures were taken by David Dalley from Village Surrey Transition Initiative…thanks Dave! and thank you to Henry for the projector and Rick for his support, you are all incredible people to have around!