Dr. Christine Jones was interviewed in the March, 2015 issue of
This article does a great job of explaining how carbon
sequestration, the secretion of sugars into the soil by plant
roots, is the absolute best method of creating wonderful, nutrient
SOS: Save our Soils
Dr. Christine Jones Explains the Life-Giving Link Between
Carbon and Healthy Topsoil
To the pressing worldwide challenge of restoring
soil carbon and rebuilding topsoil, the Australian soil
ecologist Dr. Christine Jones offers an accessible,
revolutionary perspective for improving landscape health and
For several decades Jones has helped innovative farmers and
ranchers implement regenerative agricultural systems that
provide remarkable benefits for biodiversity, carbon
sequestration, nutrient cycling, water management and
The following article is reprinted from the March, 2015
edition, volume 45, #3 of AcresUSA
Dr. Christine Jones, Interviewed
by Tracy Frisch
ACRES U.S.A. You’ve
written that the most meaningful indicator for the health of
the land and the long-term wealth of a nation is whether soil
is being formed or lost. Yet there’s a widespread belief,
actually dogma, that the formation of soil is an exceedingly
slow process. Even some organic researchers accept that idea.
You describe the formation of topsoil as being breathtakingly
DR. CHRISTINE JONES.
People have confused the weathering of rock, which is a very,
very slow process, with the building of topsoil, which is
altogether different. Most of the ingredients for new topsoil
come from the atmosphere — carbon, hydrogen, oxygen and
ACRES U.S.A. Why
have many soil scientists denied the phenomenon of rapid
Because they do their research in places where it’s not
happening, where the carbon is running down and the soils are
deteriorating. We need to measure carbon on farms where
soil-building is occurring and see what the farmers and
ranchers are doing to make that happen.
ACRES U.S.A. The
process of fixing carbon in the soil seems to be the crux of
your work. You describe a cycle with carbon in three phases:
as a gas, a liquid and a solid.
The issue we’re facing is that too much of the carbon that was
once in a solid phase in the soil has become a gas. That could
be dangerous for the human species. Climate change is just one
aspect. Food security, the nutrient density of food and the
water-holding capacity of the soil are also very potent
reasons for keeping carbon in a solid phase in the soil.
ACRES U.S.A. Your
term “liquid carbon” is such a brilliant phrase.
It has really helped me conceptualize the carbon cycle. What
do you mean by it?
carbon is basically dissolved sugar.
Sugars are formed in plant chloroplasts during photosynthesis.
Some of the sugars are used for growth and some are exuded
into soil by plant roots to support the microbes involved in
ACRES U.S.A. I remember bringing up the
idea of leaky roots in a conversation with you and you
At first people thought “leaky” roots were defective. Exuding
carbon into the soil seemed such a silly thing for plants to
do! Then it became recognized that some of the exudates were
phenolic compounds with allelopathic effects, important in
plant defense. Of course we now know that plant roots exude a
vast array of chemical substances, all based on carbon, to
signal to microbes and to other plants. But perhaps the most
significant finding, at least from a human perspective, is
flow of liquid carbon to soil is the primary pathway by which
new topsoil is formed.
ACRES U.S.A. All
of which revolves around the concept of a plant-microbial
In order for carbon to “flow” to soil, there has to be a
partnership between plant roots and the soil microbes that
will receive that carbon. Somewhere between 85 to 90 percent
of the nutrients plants require for healthy growth are
acquired via carbon exchange, that is, where plant root
exudates provide energy to microbes in order to obtain
minerals and trace elements otherwise unavailable. We
inadvertently blow the microbial bridge in conventional
farming with high rates of synthetic fertilizers or with
fungicides or other biocides.
ACRES U.S.A. Are
you observing an increased awareness of the significance of
There is a lot more energy generated through biological
processes than through the burning of fossil fuels. Most
life-forms obtain their energy either directly or indirectly
from the sun, via the process of photosynthesis. Plants are
what we call autotrophs. That is, they feed themselves by
combining light energy with CO2 to produce biochemical energy.
As heterotrophs, we obtain energy by eating plants or eating
animals that ate plants. In effect, we’re running on light
energy too. Even microbes in a compost heap are obtaining
energy by breaking down organic materials originating from the
process of photosynthesis.
ACRES U.S.A. You
distinguish between organic matter formed by the decomposition
of manure, crop residues or other carbonaceous materials — and
humus — which is generated via a building-up process. I think
a lot of times that is misunderstood.
It’s a really important distinction, but it’s often
overlooked. In order to obtain the energy that is contained in
cellulose, lignin, starches, oils, waxes or other compounds
formed by plants, microbes have to break this material down —
the same as we do when we digest starches or proteins or
anything else of plant or animal origin. We breathe out more
CO2 than we breathe in, because as we utilize the energy we
obtain from the assimilation of food, our cells release CO2.
The decomposers in the soil are doing exactly the same thing —
breaking down organic materials and releasing CO2. These
processes are catabolic. Conversely, the formation of humus is
an anabolic process, that is, a building-up process. Rather
than sugar being the end point, sugar is the start point. Soil
microbes use sugars to create complex, stable forms of carbon,
ACRES U.S.A. How
would you define humus?
Humus is an organo-mineral complex comprising around 60
percent carbon, between 6 and 8 percent nitrogen, plus
phosphorus and sulfur. Humic molecules are linked to iron and
aluminum and many other soil minerals, forming an intrinsic
part of the soil matrix. Humus cannot be “extracted” from soil
any more than wood can be “extracted” from a tree.
ACRES U.S.A. You
frequently mention mycorrhizal fungi in your work. What makes
them so special?
Much of the initial research into mycorrhizal fungi was
related to the uptake of phosphorus. Phosphorus is a highly
reactive element. As soon as there’s any free phosphorus
floating around in the soil, including whatever we may add as
fertilizer, it becomes fixed. In other words, it forms a
chemical bond with another element like iron or aluminum or
calcium, making it unavailable to plants. But certain bacteria
produce an enzyme called phosphatase that can break that bond
and release the phosphorus.
Once released, the phosphorus still has to be transported back
to the plant, which is where mycorrhizal fungi come in. As our
analytical techniques have become more sophisticated, we’ve
realized that mycorrhizal fungi also transport a wide variety
of other nutrients, including nitrogen, sulfur, potassium,
calcium, magnesium, iron and essential trace elements such as
zinc, boron, manganese and copper. In dry times they supply
Mycorrhizal fungi can extend quite a distance from plant
roots. They form networks between plants and colonies of soil
bacteria. Plants can communicate with each other via messages
sent through these networks. Mycorrhizal fungi are both the
highway and the Internet of the soil.
ACRES U.S.A. How
can something so important be overlooked?
Much of the agricultural research undertaken in pots in glass
houses is fundamentally flawed. Soil is homogenized to remove
background noise, that is, to make the soil in all the pots
similar at the outset. The blending process breaks up the
hyphae of mycorrhizal fungi. In some trials the soil is also
sterilized to eliminate any microbial activity that could
interfere with the treatment being assessed. And often the
soil has been stored for a long time prior to the experiments,
which means most of the soil organisms have died. In such an
environment, plants are likely to respond to applied
fertilizer, as they have no other means to obtain nutrients.
Similarly with field trials, if the soil has been cultivated
or bare fallowed, mycorrhizal fungi will not be there in
sufficient quantities for effective carbon flow and nutrient
acquisition. In healthy, biologically active soils, we do not
see a response to synthetic nitrogen or phosphorus
fertilizers. If anything, the use of these is
ACRES U.S.A. I’ve
learned from you that plants colonized by mycorrhizal fungi
can grow much more robustly even though they’re giving away as
much as half of the sugars that they make in photosynthesis
through their roots.
ACRES U.S.A. So
we have this system characterized by abundance and generosity,
and that’s really different from the way we are used to
thinking about growing crops.
The point that’s often missed is that a
mycorrhizal plant photosynthesizes much faster than
a non-mycorrhizal plant of the same species growing right next
to it. The plant is able to give half its energy away and
still grow stronger because of the symbiotic relationship with
the fungus. It doesn’t cost the plant anything to
photosynthesize faster. It’s just using sunlight more
efficiently. Remember, plants are autotrophic.
ACRES U.S.A. And
sunlight is free.
CO2 is free too. If
a plant photosynthesizes faster it’s going to have higher
sugar content and a higher Brix level. Once Brix gets over 12,
the plant is largely resistant to insects and pathogens.
High-Brix plants have formed relationships with soil microbes
able to supply trace elements and other nutrients that the
plant needs for self-defense, for its immune system. When
plants are able to produce high levels of plant-protection
compounds, the insects go elsewhere.
ACRES U.S.A. We
tend to think that minerals in the soil are scarce because
most of them are not in a form available to plants.
A soil test will only tell you what is available to plants by
passive uptake. The other 97 percent of minerals — made
available by microbes — will not show up on a standard test. By
looking after the microbes in the soil we can increase the
availability of a huge variety of minerals and trace elements
— most of which are not even in fertilizers.
ACRES U.S.A. We
always hear the story about fields that were continuously
cropped or hayed for 30 years where the soil is so exhausted
that we have to add a lot of nutrients or we can’t grow a
The problem is that we interrupt carbon flow with the way we
farm. Cultivating the soil and using chemical fertilizer and
pesticides break up the mycorrhizal networks. If plants can
obtain nitrogen or phosphorus easily, they will stop pumping
carbon into the soil to support their microbial partners.
It’s taken a while for people to realize that plant root
exudates are not only important for nutrient exchange, but
also essential for the maintenance of topsoil. If carbon is
not flowing to soil via the liquid carbon pathway, soil
is needed for soil structure and water holding capacity as
well as for feeding the microbes involved in nutrient
When soil loses carbon, it becomes hard and compacted. The
differences in infiltration and moisture retention between
high and low carbon soils are dramatic. Planetary stocks of
fresh water are declining alarmingly. More efficient water use
is going to be absolutely critical to the survival of our
Making better use of water requires improved soil structure —
which in turn requires actively aggregating soils. If
aggregates are breaking down faster than they’re forming, the
water-holding capacity of soil can only deteriorate.
ACRES U.S.A. How
can we tell if a soil has good aggregation?
Dig a hole and take a handful of soil. Squeeze it gently and
release. If the soil is well aggregated, it will look like a
handful of peas. If the soil remains in hard chunks that don’t
break easily into small lumps, then it isn’t well aggregated.
ACRES U.S.A. What
processes are going on inside
of a soil aggregate?
The aggregate is the fundamental unit of soil function. A
great deal of biological activity takes place within
aggregates. For the most part, this is fueled by liquid
carbon. Most aggregates are connected to plant roots, often to
very fine feeder roots, or to mycorrhizal networks unable to
be detected with the naked eye.
Liquid carbon streams
into the aggregates via
these roots or fungal linkages, enabling the production of
glues and gums that hold the soil particles together. If you
gently lift a plant from healthy soil, you’ll find aggregates
adhering to the roots. The moisture content is higher inside a
soil aggregate than on the outside, and the partial pressure
of oxygen is lower on the inside than on the outside. These
nitrogen-fixing bacteria to function.
When aggregates aren’t forming — because
of cultivating the soil or using chemicals or having bare soil
for six months or more with no green plants —
crops are not able to obtain sufficient nitrogen. The tendency
is then to add fertilizer nitrogen, exacerbating the
situation. The application of large quantities of inorganic
nitrogen interrupts carbon flow to soil, further reducing
ACRES U.S.A. It
sounds like a vicious cycle.
Yes, the more N applied, the more soil structure deteriorates
and ironically, the less N is available to plants. You’ll
rarely see a nitrogen deficient plant in a healthy natural
When I was driving home yesterday I noticed yellow, nitrogen
deficient pastures on many of the dairy farms I passed. But in
the area between the fence and the road, where no fertilizer
had been used, the grasses were a lovely dark green.
ACRES U.S.A. We
are familiar with Rhizobium bacteria and their relationship
with legumes. What should we know about free-living nitrogen
From an agricultural perspective the most important of the
freeliving nitrogen-fixing bacteria are associative
diazotrophs — so-called because the atmospheric nitrogen that
they fix occurs as di-nitrogen (N2) and associative because,
like mycorrhizal fungi, they require the presence of a living
plant for their carbon. These bacteria live in close proximity
to plant roots or are linked to plant roots via the
ACRES U.S.A. Isn’t
our knowledge of these organisms pretty recent?
The reason we know so little about associative diazotrophs is
that most cannot be cultured in the lab. This applies to most
species of mycorrhizal fungi as well. As bio-molecular methods
for detecting microbes in the soil become more sophisticated,
we’re realizing there is a lot more life — and a lot more
species — than we thought. It has become obvious that there
are thousands of different types of bacteria and archaea that
can fix nitrogen.
The Haber-Bosch process, by which we manufacture nitrogen
fertilizer, is a catalytic reaction requiring enormous amounts
of energy. Yet microscopic bacteria in the rhizosphere or
within plant-associated aggregates can fix nitrogen simply
using light energy from the sun, transformed to biochemical
energy during photosynthesis and channeled to soil by plant
ACRES U.S.A. I’m
a little confused because I understood that there is a
difference between mineral nitrogen and organic nitrogen.
That’s correct. Nitrogen fixing bacteria produce ammonia, a
form of inorganic nitrogen, inside soil aggregates and
rhizosheaths. Rhizosheaths are protective cylinders that form
around plant roots. They’re basically a bunch of soil
particles held together by plant root exudates. You can easily
strip them off with your fingers.
Within these biologically active environments the ammonia is
rapidly converted into an amino acid or incorporated into a
organic forms of nitrogen cannot be leached or volatilized.
Amino acids can be transferred into plant roots by mycorrhizal
fungi and joined together by the plant to form a complete
On the other hand, inorganic
nitrogen applied as fertilizer often ends up in plants as
nitrate or nitrite, which can result in incomplete or “funny”
This becomes a problem in cattle if it turns up as high levels
of blood urea nitrogen (BUN) or milk urea nitrogen (MUN).
Nitrates cause a range of metabolic disorders including
infertility, mastitis, laminitis and liver dysfunction. There
is also a strong link between nitrate and cancer. In some
places in the United States it is not safe to drink the water
due to excessive nitrate levels. Milk can also have nitrate
levels above the safe drinking standard, but people happily
consume it, not realizing it’s unhealthy.
ACRES U.S.A. These
are great points. How dependent is the world on the
application of synthetic nitrogen?
Farmers around the world collectively spend about $100 billion
per year on nitrogen fertilizer. I’m greatly inspired by the
multi-species over crop revolution in the United States.
Leading-edge farmers like Gabe Brown, Dave Brandt and Gail
Fuller are showing it’s possible to maintain or even improve
crop yields while winding back on fertilizer. These farmers
are light years ahead of the science.
They’re building soil, improving the infiltration of water,
increasing water holding capacity and getting fantastic
yields. They have fewer insects and less disease. The carbon
and water cycles are fairly humming on their farms.
ACRES U.S.A. I
want to get your recipe for transforming terra-cotta tile into
chocolate cake — that is, turning hard, compacted soil into
loose, fragrant soil teeming with life.
There isn’t a “recipe” as such for maintaining soil aggregates
(the starting point for chocolate cake). It’s really just a
set of guiding principles. Soil becomes like a terra-cotta
tile when aggregates break down. Hard, compacted soil sheds
water. The amount of effective rainfall is dramatically
reduced. It’s also much harder for plant roots to grow in
poorly aggregated soil.
The first rule for
turning this around is to keep
the soil covered,
preferably with living plants, all year round. In
environments where the soil freezes, it’s still important to
maintain soil cover with mulch or a frost-killed cover crop or
better still, a frost-hardy cover that will begin to grow
again as soon as spring arrives.
Microbes will go into a dormant phase over winter and
re-activate at the same time as the plants. In regions with a
hot, dry summer, evaporation is enemy number one. Bare soil
will be significantly hotter and lose more moisture than
covered soil. Aggregates will break down unless the soil is
alive. Aggregation is absolutely vital for moisture
infiltration and retention.
ACRES U.S.A. OK,
so that’s one.
diversity in both cover crops and cash crops.
Aim for a good mix of broadleaf plants and grass-type plants
and include as many different functional groups as possible.
Diversity above ground will correlate with diversity below
or minimize the use of synthetic fertilizers, fungicides,
insecticides and herbicides.
It’s a no-brainer that something designed to kill things is
going to do just that. There are countless living things in
soil that we don’t even have names for, let alone an
understanding of their role in soil health. It’s nonsense to
say biocides don’t damage soil! In Australia many farmers
plant seeds treated with fungicide “just in case.” They’re
actually preventing the plant from forming the beneficial
associations that it needs in order to protect itself.
After a few weeks of crop growth, they will then apply a
“preventative” fungicide, which also finds its way to the
soil, inhibiting the soil fungi that are essential to crop
nutrition and soil building. The irony is that plants are then
unable to obtain the trace elements they need to fight fungal
diseases. We see many examples of crops grown biologically
that are rust-free, side-by-side with rust infected plants in
neighboring fields where fungicides are being used.
There is an analogous situation with human health. Not that
long ago the cancer rate was around one in 100. Now we’re
pretty close to one in two people being diagnosed with cancer.
At the current rate of increase, it won’t be long before
nearly every person will contract cancer during their
lifetimes. Cancer is also the number one killer in dogs. Isn’t
that telling us something about toxins in the food chain?
We’re not only killing everything in the soil, we’re also
killing ourselves — and our companion animals. Is that what we
want for our future?
ACRES U.S.A. Are
you a cancer survivor?
Yes, I am, which is basically why I do what I do. But I don’t
say a lot about that because if you start your talk with
“we’re all going to die from cancer unless we change,” people
tune out. It’s too threatening. Most of us have lost loved
ones through cancer.
ACRES U.S.A. You
say it’s not just the toxins in our food that are the problem,
but the use of biocides — chemicals that kill living organisms
— which reduce the nutrient content of food. And you attribute
that nutrient reduction to the inhibition of the
Spot on. If the plant-microbe bridge has been blown, it’s not
possible for us to obtain the trace elements our bodies need
in order to prevent cancer —
and a range of other metabolic disorders. Cancer is not a
transmissible disease. It’s simply the inability of our bodies
to prevent abnormal cells from replicating. To date, the
response to the cancer crisis has revolved around constructing
more oncology units, employing more oncologists and
undertaking more research. The big breakthrough in cancer
prevention will be in changing the way we produce our food.
ACRES U.S.A. We
have plenty of evidence from meta-studies that the nutrient
content of produce grown organically tends to be higher than
produce grown chemically. We also have documentation of steep
declines in nutrient content in a number of foods over the
Yes, we’re getting a double whammy. We’re ingesting chemical
residues, but not the trace elements and phytonutrients we
need for an effective immune response. Plants need trace
elements, like copper and zinc, to make these phytonutrients.
But the trace elements will not be available in the absence of
an intact microbial bridge.
ACRES U.S.A. You’ve
talked about the pressure on farmers to have tidy farms and
uniformity in their fields. It seems like one of the problems
you’re identifying is a faulty understanding of what it means
to farm well and to be a good farmer. What are some of the
qualities that farmers think they should have that get in the
way of building healthy soil?
I must admit that in the early ’90s, when I first started
going onto farms that were using holistic planned grazing, I
was a bit shocked to see the number of weeds popping up. These
weeds would have been sprayed under the former management
regime, but the ranchers were saying, “Don’t worry. We
have to pass through this weedy stage.
If we spray weeds, we create bare ground and the weed seed
that’s there means the weeds simply come back.”
There’s a saying, “the more you spray weeds, the more weeds
there will be to spray.” It’s oh so true! Continually
reverting to bare ground creates more problems than it solves.
Those ranchers knew some weeds had deep roots that bring up
nutrients. Leaving them there meant better
quality plants would eventually be able to grow in the
improved soil and replace the weeds.
That is exactly what happened. Over the last 60 years we’ve
tried — and failed — to control weeds with chemicals.
One of the exciting things about the multi-species cover crop
revolution that’s underway in the United States is that the
greater the variety of plant types you use, the more niches
you fill and the less opportunities there are for weeds.
Cover-crop enthusiasts are experimenting with 60 or 70
different species in their mixes. I see the trend to
polyculture as the most significant breakthrough in the
history of modern agriculture. Even so, the first time you see
a multi-species cover or a cash crop grown with companion
plants, you might think, “Wow, that looks untidy” because
we’re not used to it. It takes a little while to realize that
having all those different plants together is really
Somehow we have to change the image of what a healthy field
looks like so that when people see bare ground or a
monoculture, they recognize it’s lacking — and that this is
not a good thing.
ACRES U.S.A. What
sort of response are the cover crop pioneers receiving?
They’re seeing fantastic results. The trouble is they are not
getting the accolades they deserve. This is slowly beginning
to change. NRCS, in particular, are being exceptionally
supportive of these leading edge farmers. Cover cropping is
now generating a huge amount of interest.
Recently I visited Brendon Rockey, a young potato farmer in
the San Luis Valley of Colorado. Brendon has increased
irrigation efficiency 20 percent through the use of cover
crops. There is increasing worldwide recognition of the fact
that multi-species cover crops improve soil-water
ACRES U.S.A. Right,
another aspect of that abundance.
If there is a bare fallow between crops — or bare ground
between horticultural plantings such as grapes — soil
aggregates break down.
As a result, water cannot infiltrate as quickly. It remains
closer to the surface and evaporates more readily. Lack of
aggregation also renders the soil more prone to wind and water
We have this fear that if we grow companion plants or a cover
crop, they’re going to use up all the water and nutrients. We
have to realize that by supporting soil microbes, a diversity
of plants actually improves nutrient acquisition and water
ACRES U.S.A. In the
transition period from a chemically intensive system where you
don’t have a functioning plant-microbial bridge,
what are some kinds of practices that farmers can use?
Sometimes when farmers realize the importance of soil biology
stop using fertilizers and chemicals.
This is not necessarily a good thing. It takes time for soil
microbial populations to re-establish. If the soil is
dysfunctional, chances are the wheels will fall off when
fertilizers are pulled. If there is a failure, farmers will
revert back to what they know ... chemical agriculture.
You have to wind back slowly and accept that it’s going to
take time to transition. The key to getting started is to
experiment on small areas. It’s a matter of dipping a toe in
the water. Include some clovers or peas with your wheat, or
vetch with your corn — just on one part of the field.
This reduces the risk. When farmers see that they’ve gained
rather than lost yield — and that the crop looks healthier —
they will be inspired to try a larger area and a greater
variety of companion plants next time. Another option is to
plant a multi-species cover crop on part of the land that
would normally be devoted to a cash crop.
You’re exceptionally lucky in the United States in that a lot
of farmers are experimenting with cover crops now. Once the
diversity ramps up, the ladybirds and lacewings and predatory
wasps appear and the need for insecticides falls away. And
after heavy rain, it’s obvious that water has infiltrated
better in the parts of the field where the cover crops were.
Gradually the changes become an integral part of farming — an
exciting part, in fact. Experimentation and adaptation become
the norm, rather than conformity. Confidence builds, as ways
to restore healthy topsoil become firsthand knowledge.
ACRES U.S.A. What
It’s important to cut back on chemical fertilizers slowly. If
you’ve been using loads of synthetic nitrogen, then
free-living nitrogen-fixing bacteria won’t be abundant in your
soil. An easy way to transition is to reduce the amount of
nitrogen applied by around 20 percent the first year, another
30 percent the next and then another 30 percent the year
At the same time as reducing fertilizer inputs it’s absolutely
vital to support soil biology with the presence of a wide
diversity of plants for as much of the year as possible.
Another way to gradually reduce fertilizer inputs is to use
foliar fertilizers rather than drilling fertilizer under the
seed. Foliar-applied trace minerals can also help during
transition. These can be tank-mixed with biology-friendly
products such as vermi-liquid, compost extract, fish
hydrolysate, milk or seaweed extract.
Whichever path you choose to support soil biology, the overall
aim is for soil function to improve every year. The overuse of
synthetic fertilizers will have the opposite effect.
ACRES U.S.A. You
mentioned the longest-running field experiment in North
America that found that high nitrogen depletes soil carbon?
The Morrow Plots are the oldest continuously cropped
experimental fields in the United States. A team of University
of Illinois researchers investigated how the fertilization
regimes that were commenced in these plots in 1955 affected
crop yields and soil carbon and organic nitrogen levels.
They discovered that the fields
that had received the highest applications of nitrogen fertilizer
had ended up with less soil carbon — and ironically less
nitrogen — than the other fields.
The researchers concluded that adding nitrogen fertilizer
stimulated the kind of bacteria that break down the carbon in
the soil. The reason there is less nitrogen in the soil even
though more has been applied is that carbon and nitrogen are
linked together in organic matter. If carbon is decomposing,
then the soil will also be losing nitrogen. They decompose
ACRES U.S.A. That’s
fascinating. Tell me about David Johnson and what he is
finding in his research at New Mexico State University.
Dr. David Johnson is based in Las Cruces, south of
Albuquerque. He has discovered that the ratio of fungi to
bacteria in the soil is a more important factor for plant
production than the amount of available nitrogen or
Sadly, in most of our agricultural soils, we have far more
bacteria than fungi. The good news is that farmers use
multi-species cover crops, companion crops, pasture cropping
and other polycultures — and the ranchers who manage their
perennial grasses with high density short duration grazing
accompanied by appropriate rest periods — are
moving their soils toward fungal dominance.
When you scoop up the soil, it has that lovely composty,
mushroomy sort of smell that indicates good fungal levels.
Oftentimes agricultural soils have no smell or a smell that is
a bit sour. Fungi are important for soil carbon sequestration
as well as nutrient acquisition. The formation of humus, a
complex polymer, requires several catalysts, including fungal
ACRES U.S.A. That
is a really interesting insight. I would like to get some
perspective on soil degradation. You’ve written about how lush
and green Australia’s landscape was at the time of European
settlement in the early 1800s, land that’s now desertified.
How do your readers react?
They have a particularly hard time believing that the southern
and southwestern parts of Australia supported green plants
during our hot, dry summers. It’s fortunate that some of the
first European settlers kept journals. George Augustus
Robinson, who was the Chief Protector of Aborigines, kept a
daily journal for several years.
Robinson was a keen observer. He made sketches of the
landscape as well as describing it. In summertime when it was
over 100 degrees and without rain for months on end, Robinson
noted green grass and carpets of wildflowers everywhere he
looked. Sadly, we don’t know what many of these plants were
because we no longer have wildflowers in some of the colors he
ACRES U.S.A. Could
you reconstruct what happened to destroy all this lush,
European colonists brought boatloads of sheep which rapidly
multiplied. In England you could have sheep in continual
contact with the grass and it didn’t matter greatly because it
nearly always rained. Australian weather tends to oscillate
between drought and flooding rain and the English weren’t used
to that. By the late 1800s there were many millions of sheep
in Australia, grazing the grasslands down to bare earth in the
When it rained, the unprotected soil washed away. The river
systems and wetlands filled with sediment. We’re now farming
on subsoil. We’ve lost around 2 to 3 feet of topsoil across
the whole country. The original soil was so well aggregated
that aboriginal people could dig in it with their bare hands.
The first Europeans to arrive in Australia talked about two
feet of black “vegetable mold” that covered the soil surface.
Today our soils are mostly light-colored. The use of color to
describe soils only came into being after the carbon-rich
topsoil had blown or washed away. It’s not an uncommon story.
Just about every so-called civilized, developed country in the
world has lost topsoil by one means or another. In the States
you had your Dust Bowl, created by tillage. Restoring the
health of agricultural soils will require more than learning
how to minimize soil losses. We
need to learn how to build new topsoil, and we need to learn
how to do it quickly.
ACRES U.S.A. I
read that in Australia, using the so-called best management
practices of stubble retention and minimal tillage, wheat
production results in the loss of 7 kilograms of soil for
every kilogram of wheat harvested. Is it still that bad?
Yes, probably worse. I have documented evidence of 20 tons of
soil per hectare per year being lost through wind erosion. The
average wheat yield in Australia is very low, around 1 ton per
hectare. We lose massive amounts of soil to achieve it. The
current situation is not sustainable.
ACRES U.S.A. How
much of Australia’s farmland would have to increase soil
carbon to offset your country’s carbon emissions?
It would require only half a percent increase in soil carbon
on 2 percent of our agricultural land to sequester all
Australia’s CO2 emissions. Our emissions are low in relation
to our land area because we have a relatively small
ACRES U.S.A. Do
you have any idea worldwide how much farmland would have to be
managed differently to increase soil carbon sufficiently to
reverse global climate change or offset greenhouse gases?
Agriculture is the major land use across the globe. According
to the FAO there are around 1.5 billion hectares of cropland
and another 3.5 billion hectares of grazing land. Currently
much of that land is losing carbon.
No doubt there will be — and indeed there already have been —
endless arguments about how much carbon can be sequestered in
soil. In my view it’s not a matter of how much but how many.
The focus needs to be on transforming every farm that’s
currently a net carbon source into a net carbon sink.
all farmland sequestered more carbon than it was losing,
atmospheric CO2 levels would fall at the same time as farm
productivity and watershed function improved. This would solve
the vast majority of our food production, environmental and
human health problems.
I’m disappointed to see that articles are still being
published in internationally recognized peer-reviewed soil
science journals — as recently as 2014 — downplaying the
potential for carbon sequestration in agricultural soils.
Predictably, these articles fail to mention plant roots,
liquid carbon or mycorrhizal fungi.
Many scientists have confused themselves — and the general
public — by assuming soil carbon sequestration occurs as a
result of the decomposition of organic matter such as crop
In so doing, they have overlooked the major pathway for the
restoration of topsoil. Activating the liquid carbon pathway
requires that photosynthetic capacity be optimized.
There are many and varied ways to achieve this. I have
enormous respect for the farmers and ranchers who have done
what the experts say can’t be done. If we have a future, it
will be largely due to the courage and determination of these
ACRES U.S.A. You
initiated the Australian Soil Carbon Accreditation Scheme
(ASCAS). I’m quite impressed that one person started something
I launched ASCAS in 2007 out of frustration that the federal
government wasn’t doing anything to reward innovation in land
management. I wanted to demonstrate that leading edge farmers
could build carbon in their soils and be financially rewarded
for doing so. But my attempts were blocked at every level,
including being subjected to public ridicule.
I suspect much of the resistance stemmed from the fact that
Australia was importing over $40 billion worth of farm
chemicals and policy-makers saw that as a big business. They
realized that in order to build soil carbon, farmers would
need to reduce chemical use. There were other issues too.
Australia ratified the Kyoto Protocol nine months after the
launch of ASCAS. Under Kyoto Protocols, the issuance of carbon
credits requires adherence to the 100 year rule, which
basically means that any payment for soil carbon must be
registered on the land title and the money refunded if for any
reason the carbon levels fall over the ensuing 100 years.
Then there’s the additionality rule, which states farmers
cannot be paid for changes in land management that they would
have made anyway, or that result in higher profits.
ACRES U.S.A. You
said this story has a good ending.
Despite the roadblocks, I felt it was important that soil
restoration pioneers be recognized. Late last year we decided
to discard the original ASCAS model and start afresh. On March
19, 2015, almost eight years to the day after we launched the
ASCAS in 2007, our patron Rhonda Willson will present 11 Soil
Restoration Leadership Awards at a farming forum in Dongara,
Western Australia. It’s a fitting conclusion that these awards
be presented in the International Year of Soils.
ACRES U.S.A. What
changes did your Soil Restoration Leaders make in order to
improve soil function?
The agricultural region of Western Australia experiences an
extremely hot, dry summer. Winters are cool and moist,
although not as moist as many farmers would like. Innovative
ranchers have been planting summer active grasses at the end
of winter when there is sufficient moisture for germination,
despite ‘expert’ opinion that it’s too hot and dry in summer
for anything to grow. Perennial grasses have incredibly deep
root systems and form mycorrhizal associations that help them
The grasses soon create their own microclimate. It’s an
absolute delight to see these patches of green in an otherwise
parched landscape. It helps us understand how the countryside
encountered by the first European settlers was able to remain
green over the summer.
ACRES U.S.A. At
the People’s Climate March in New York City, a large
contingent of vegan activists carried signs blaming cattle as
a major cause of global warming. What are your thoughts on
targeting ruminants for greenhouse gas emissions?
There were more ruminants on the planet 200 years ago than
there are now, but we’ve gone from freeranging herds to
animals in confinement. That changes everything.
Firstly, we’re growing feed for these animals using
fossil-fuel intensive methods and secondly, confinement
feeding creates a disconnect between ruminants and
methanotrophs. Methanotrophic bacteria use methane as their
sole energy source. They live in a wide variety of habitats,
including surface soils. If a cow has her head down eating
grass, the methane she breathes out is rapidly metabolized by
There’s an analogous situation with termites. Termites produce
methane during enteric fermentation, as happens in the rumen
of a cow. But due to the presence of methanotrophic bacteria,
methane levels around a termite mound are actually lower than
in the general atmosphere.
nature, everything is in balance. After the disastrous
Deepwater Horizon oil spill in the Gulf of Mexico, the ocean
was bubbling with not only oil, but also methane. To the
astonishment of scientists monitoring the spill, populations
of methanotrophic bacteria exploded and consumed an estimated
220,000 metric tons of methane gas, bringing levels back to
ACRES U.S.A. When
we talk about the consequences of the increased extreme
weather associated with climate change, like devastating
floods and droughts, all too often we neglect to
consider how better land management can reduce their impacts.
With weather events becoming more extreme our farming systems
need to be more resilient. Again, this is where having carbon
sequestered in soil to maintain aggregate stability and
improve infiltration is vitally important.
If we look at flooding on the Mississippi,
for example, we see that the mean maximum and mean minimum
water levels from the early 1800s to the present show an
increasing perturbation since the dust bowl era of the 1930s.
That is, the highs are becoming higher — floods are more
severe — and the lows are getting lower — the river doesn’t
‘run’ as much as it used to.
This boom-bust situation is due to inappropriate land
management. If soil is in good condition, water infiltrates
rapidly and is held in the soil profile. Some of this water is
used for plant production and some will move downward through
the soil to replenish the transmissive aquifers that feed
springs and small streams, enabling year-round, moderated
baseflow to river systems.
If groundcover is poor and soil water-holding capacity is low,
rapid run-off not only leads to flooding in lower landscape
positions, but also takes a lot of topsoil with it. These days
it’s not just soil, but a heap of chemicals too — which end up
in the Gulf of Mexico.
ACRES U.S.A. Causing
the Dead Zone?
Yes. The consequences are enormous. And when the flood is
over, the river level drops because the transmissive aquifers
haven’t been recharged.
ACRES U.S.A. Is
adding compost to the soil sufficient to turn things around?
Compost is certainly a fantastic product, but compost alone is
not enough. It will eventually decompose, releasing CO2.
However, the application of compost to appropriately grazed
pastures or polyculture crops can increase plant growth and
photosynthetic rate, resulting in more liquid carbon flowing
Diverse microbial populations — particularly fungi — supported
by the compost, can aid in humification, improving soil
structure, water-holding capacity and nutrient availabilities.
On large agricultural holdings such as we have in many parts
of Australia, it is not economically viable to spread compost.
However, compost extract, which is simply the chemical
signature of compost, can prove highly beneficial.
The use of natural plant or seaweed extracts as bio-stimulants
is a relatively new but rapidly expanding area of R&D and
farmer-adoption worldwide. The advantage of bio stimulants is
that they function at very low rates of application —
milliliters per hectare — as opposed to a product such as
compost which needs to be applied in tons per hectare.
These products stimulate soil biota and enhance plant root
function. The proliferation of roots is quite obvious when you
dig in the soil. There can also be rapid improvements in soil structure.
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