Rethinking
Organics
Soil Health and Climate Change as the
New Compost Industry Drivers
The Soil is Alive!

“The soil is the great
connector of our lives, the
source and destination of
all.” - Wendell Berry, The
Unsettling of America, 1977
Source of Images:
Soil and Water Conservation Society.
SWCS. 2000. Soil Biology Primer. Rev.
ed. Ankeny, IA: Soil and Water
Conservation Society
What is “soil health”?

One handful of garden
soil: more living
organisms than there are
people on the planet
Soils
=
 This web of soil
Living
organisms – predators
and prey – are
Ecosystems
responsible for about 90%
of the soil functions that
make above-ground life
possible
Soil Ecosystems – The Basics
“Who eats
whom”, and
why it
matters…
Source: Soil and Water Conservation Society
Bacteria

Microscopic: fraction of a
micron diameter; a few
microns in length
(micron = one millionth
of a meter)

Many millions in a
teaspoon of soil

3 main functional
groups: decomposers,
mutualists, pathogens

A productive soil has the
bacterial biomass
equivalent to 2 cows per
acre
Source: Soil and Water Conservation Society
Fungi
3 types of soil fungi:
Decomposers (saprophytic fungi)
Mutualists (mycorrhizal fungi)
Plant parasites (pathogenic fungi)
Source: Soil and Water Conservation Society
-Grow as long threads, known as “hyphae”, which
are just a few microns in width
-Mycelia are groups of hyphae massed together
(these are often visible)
- Important decomposers, breaking down tough
materials, such as lignin
Protozoa
-Also single celled,
but more organized
cell structure
-Several times larger
than bacteria
-Consume bacteria,
each other, some
fungi
Source: Soil and Water Conservation Society
-Example: amoebae
Nematodes

Microscopic unsegmented worms

Many different kinds of nematodes

Beneficial ones include those that
eat bacteria and fungi, as well as
the larger predatory nematodes
that eat the smaller species

Root feeders are the ones that
cause plant damage;

The latter can be controlled by the
predatory nematodes if conditions
for the predators are good
Source for both images: Soil and Water
Conservation Society
The Soil Food Web is a Community

Like our own communities, it
organizes itself to optimize
conditions for its members

To do this, it uses the energy
that comes from the aboveground ecosystem

For example, the community
organizes a soil structure
similar to our community
infrastructure
Soil Food Web is a Community - 2

Other services that this
community creates include
(but are not limited to):
 resource
extraction and
recycling;
 food
production and
harvesting;
 Transportation
services;
 Communications;
 Health
and welfare.
Soil Health and Climate: The
Original Carbon Trading Scheme
Two basic systems:
Up to 44% of
photosynthate exuded into
rhyzosphere
1.
Plant root exudates
2.
Mycorrhizal fungi
Two-way delivery system – nutrients
traded for C compounds
Source: Soil and Water Conservation Society
11
Microbes: Soil Structural
Soil organisms within a soil
Engineers
aggregate

Bacteria, earthworms
secrete organic glues,
bind particles of clay,
silt, sand into tiny
aggregates

Fungal hyphae
(filaments) bind these
into larger soil
aggregates

Well-aggregated soils are
ideal environment for
both microbes and plant
roots
Source: Soil and Water
Conservation Society
12
From a societal perspective, healthy soils
are key to:

Climate change
 GHG
emissions
 Adaptation/resilience

Pesticide use (& effects)

Soil erosion and sedimentation

Water quality (e.g., Lake Erie)

Biodiversity (incl. pollinators)

Not just an issue for
agriculture!
13
Role of Compost in Soil Health


Compost provides SFW
with:

Food (energy)

Habitat

Diversity (organisms)
These provisions increase
the size and diversity of
the SFW
Source: Soil and Water Conservation Society
Role of Compost in Soil Health - 2

New scientific support for the idea that we can use compost to improve
F:B balance of SFW

Dr. David Johnson, University of New Mexico, good results from increasing
F:B ratio in compost
Johnson – Indoor Trial Results

As F:B ratios increased:
C
fixation increased until F:B
hit 1.6, then leveled off
fixed C goes mostly
(97%) to soil at low F:B, then is
diverted to shots and fruit
(yield!) as F:B increases
Energy!
 Newly
 Existing
C respired at high rates
at low F:B (44%), decreased to
lower rates (11%) at high F:B
Yield!
SOM!
Johnson – Outdoor Trial
Results

Methods: no-till, multi-species cover crops, total,
constant ground cover, plus:


Inoculation with fungal-dominant compost
Results after 19 months:

Soil C went from 0.87% to 7.6%

F:B ratio from 0.8 to 4.3

Above ground biomass production increased from 1980 to
8450 g/m2/yr

Despite large increase in soil C, respiration rates only
doubled

Annual average capture & storage of C of 10.27 tonnes/yr
Some Cautions

Single study, needs to be replicated in other places
(how about Ontario?)

Only sampled soil C to a foot in depth – what is
happening further down?

These rates of increase will likely taper off as soil
reaches a new equilibrium (but at what level?)

Need more research into optimal F:B ratios –
Elaine Ingham suggests optimum different for
different crops – has not been documented in
rigorous scientific studies.

This study suggests that compost is most important
as an inoculant – more work required to determine
the potential of compost in this regard.
Soil and Climate Regulation:
How do soils sequester carbon?

Used to be thought that soil carbon
came solely from organic residues

Therefore, to sequester carbon in soils
-- leave residues, add manure,
compost

Now understood that most of the C
sequestered comes through plant roots
(original C trading system)
Source: Soil and Water Conservation Society
19
Reference
Notes
Sequestration
(tCO2e/ha/yr)
IPCC
Basic rate based on literature
1.1
Italy
50-year comparison
3.0 - 3.5
Rodale
Composted manure
4.8 – 8.4
Marin C Project
Each year for several years after one
application of food-waste compost to
rangeland
3.7
Compost and Soil
Carbon
Sequestration
Compost and Soil Carbon
Sequestration - 2
 Dr. Whendee Silver, UC Berkeley – Marin Carbon Project
 4000 cu yds of food-waste compost on 100 acres of rangeland
 50 per cent increase in forage production
 Increase of one tonne of C (3.7 t CO2e) per ha for three years
after single application
 American Carbon Registry –
 Developed offset protocol for application of compost to
rangelands
NOTE: Soil C not primarily from compost – it comes from
the SFW!
The Confusing Inconsistencies

Compost can suppress
disease; but sometimes, it
does not

Compost boosts yields a
lot, or maybe just a little

Compost can sequester a
lot of carbon, or a little?

Why are the results not
more consistent?
Confronting the Inconsistencies; Embracing
the Opportunities

Benefits of compost not direct,
but a result of an enhanced SFW

if other practices are
destructive, compost benefits
will be muted or lost

The value of compost must be
assessed in a soil-health context
Embracing the Opportunities - 2
We need to make the case for
compost application to soil as an
important soil health BMP

BMPs such as cover crops work
by protecting and feeding the
SFW

Compost also feeds the SFW,
plus:

provides immediate habitat

increases diversity quickly,
via the introduction of new
types of beneficial organisms
 Compost also offers a quick
way to increase soil fungal
populations
 Compost is also a potential tool
for immediate remediation of
farm soil (e.g., after a
fungicide application)
Opportunities
1.
We need to shift thinking from waste management mindset to a soilhealth mindset
2.
In doing so, they need to keep these ideas in mind:

Soil-health BMPS and compost could be a match made in heaven,
but first the case needs to be made for compost’s unique
contribution

Compost Quality Alliance is a good vehicle for moving forward,
because not every compost is suited to every application

The potential of soil-carbon sequestration via compost application to
soils is worth exploring further….

As is the potential of carbon offsets
Compost Council of Canada in
2017 -
Launching a new Soil Health Initiative

Components:
A
Soil Health Primer
 Template
for a one-day workshop on
soil ecology and soil health
A
web page with information update,
interactive quizzes, blogs, etc.
Final Thoughts
 Soil
health a vitally important new
paradigm (that extends beyond
agriculture and into the realm of
general sustainability)
 Soil health is a significant tool in our
climate-change arsenal
 We still have much to learn about the
soil food web and how we could
optimize its value to those of us above
ground
 Compost has a key role to play in the
soil health movement
Thank you!