Thoughts on Soil Fertility

What makes soil fertile? How can my soil provide what a plant needs? Andwhat can I do to make sure this happens this year? These questions fill our house in spring, as winter’s farming ideas start to take shape.

There’s a tendency these days to take the quick and easy route.  If
there’s a question or a problem, we want an answer or solution.  We want
it now, we want it here, we want it cheap, and it helps if we can pick up
some soda and dog food while we’re at it.  The “conventional” way of going
about soil fertility (which isn’t really conventional, given it’s only
decades old) is to send a soil sample to the University, get a read-out of
nutrient deficiencies, and accept a recommendation for how many pounds of
10-10-10 to apply.  It’s here, it’s now, and it’s cheap.

Many people understand the problems of this kind of thinking when it comes to farming.  While lab tests may show
certain nutrients are needed, and synthetic fertilizers may make a plant
green, we sense there is much more to soil than a read-out of nutrients,
and that there is no synthetic substitute for a healthy, living soil.

But there are a thousand ways to go from there.  Hit the books, and you’ll
find hundreds of takes on soil fertility.  Talk to farmers, and you’ll
hear a different perspective from each one you ask.  Surf the internet and
find more information than your eyes should handle.

A few broad concepts they all seem to agree on: organic matter, cover
crops, manure and composts are good.  Plants need certain nutrients, and
soils need to be balanced.  Biodiversity is key, and reduced, careful
tillage is essential.  But what do these broad concepts mean for me, when
it comes time to start making decisions about what to do in 2010?

This isn’t a sob story, but ultimately, when making decisions on the farm,
we are terribly alone.  Sure, there are broad concepts, but no one has
faced the decisions I am making, about this farm, right now.  The
following is a discussion of some of the ideas and experiences that form
the basis for my soil fertility decisions, for what it’s worth...

This year I “upgraded” from the University soil tests and coughed up the
$25 for a “better” soil test that contained things like organic matter
content, estimated Nitrogen release, cation exchange capacity, and percent
base saturation for Potassium, Magnesium, Calcium, and Sodium.  If that
sounds a little involved to you, that’s because it is.  Trying to figure
out the science of your soil given the tests available isn’t the easiest
homework assignment there is.  I’ve heard tales of farmers who could chew
on a tiny bit of soil and tell you what needed to happen based on taste
and feel.  If you know of one, tell them to call me, by all means.

As I tried to interpret these test results, a few things stuck out.  There
were deficiencies in a few nutrients (Boron, Zinc, Copper, and Magnesium),
and the “percent base saturation” of Potassium, Magnesium, Calcium and
Sodium were less than ideal.  A few weeks earlier I had heard a popular
Biodynamic farmer, Jeff Poppen, aka “The Barefoot Farmer” (and author of
the book by the same name), mention that you want a certain relationship
between levels of Potassium, Magnesium, Calcium, and Sodium.  And a book
by Gary Zimmer, “The Biological Farmer”, validated this idea.  (Both books
I highly recommend.)   By this point I accepted that my soils are
deficient in some nutrients and that the high “base saturation” of Calcium
and Potassium may contribute to a Magnesium deficiency.



What do you do when a soil is deficient or imbalanced?  The Biological
Farmer’s perspective suggests supplying any limiting nutrients, in part,
with rock applications based on soil tests.  Greenview Farms Coop in Ohio
helped me develop a custom mix based on my soil tests.  For three acres
it contains:  500 lb of a mix of several kinds of rocks (sulphate of
potash, magnesium sulphate, boron, zinc, and copper), to supply limiting
nutrients, humates (plant deposits that are almost coal) for humic acid
to improve soil structure and feed microbes, molasses to feed microbes,
kelp (seaweed) for minerals and nutrients, and beneficial bacteria and
fungi.  All in all, about a $150/acre treatment, for those of you keeping
track.

Now I don’t know about you, but I’m constantly striving to reduce inputs
and costs, and I’m well aware of the dangers of relying on industrial
systems that use a lot of energy.  I wrestle with this idea that my farm
“needs” to import rocks from Utah, or that it relies on mining and
pulverizing that uses massive amounts of energy.  Isn’t there an on-farm
or local alternative?  Maybe in time these answers will come.  For now,
this is just “where we’re at”: farms that aren’t yet ideal, plenty of good
questions, and lots of work to figure them out.

To complicate things, I have questions surrounding application techniques.
When is it best to apply rocks, humates, and microbes?  Before a rain or
in the sun?  Just before you till or onto a growing cover crop?  Waning or
waxing moon?!?  Members of the Greenview coop suggested, “As soon as
possible right onto the cover crop.  The cover crop will take up the
minerals and if tilled in as a green manure, it will be cycled back into
the soil.”  Makes sense.   But when I started spreading, something didn’t
seem right.  Leaving the microbes and rocks baking in the direct sun
seemed wrong.   Fearing a waste of money, I decided to try another method.
Philip Lyvers (of Lyvers Farm, a 2,600 acre hog operation in Kentucky
integrating Biodynamic practices into a conventional system) suggested
that any fertility inputs be “buffered” with compost.  My interpretation
is this: the ideal farm uses on-farm compost from animals and materials on
the farm.  This stimulates a build-up of microbes in composts that is well
adapted to your soils.  By putting mineralizing materials into the
compost, you “introduce” the composts to the rocks and increase the rate
and potential for the rocks to act on your soils.  Considering Philip’s
farm hasn’t gone the way of almost every other hog producer in Kentucky
(he’s still farming), I figure there’s a good chance his advice is solid.
So I will be adding about 1/3 of the rock mix to composts and adding that
mixture just before spring tillage.

Speaking of compost and microbes, plants need more than just a balanced
soil; they need a live soil high in microbial life and organic matter.
Sounds simple enough.  But again, how do I make decisions that will
support soil life and organic matter?

For instance, we hear that green manuring is a good idea.  By
incorporating cover crops into the soil, we can increase soil organic
matter and feed soil microbes.  And yet we also know that tillage is
destructive.  With each tilling of the soil, microbial populations
drastically drop and some even vanish from our topsoil.  A friend asks:
“If tillage is bad, then why till in a cover crop?  Why not just cut it
and allow it to mulch on top of the soil?”  Good questions.  No-till
proponents say to leave the roots undisturbed; if you can kill the cover
crop with mowing or crimping and leave the root zone undisturbed, those
roots die and leave all their exudates and microbial allies in the soil
for your next crop to utilize.  Tilling would only wreak havoc on these
fragile, important organisms.  Other people may point us toward studies
that show that incorporation of cover crops increases organic matter and
microbial diversity more than no-till strategies.  Ultimately the decision
to till or not to till depends on many factors, and each of us must weigh
those factors independently.

Similar questions arise with animal manures.  It is well-known that animal
manures are a good thing for soils.  (Although I’ve read that some vegans
have taken up gardening/farming and are working on systems that use no
animal manures or confined animals of any kind.)  In my mind, the “ideal”
farm puts animals and crops together, and fertility needs of the crops are
met with the manures of the animals (including people).  But let’s look
again at “where we’re at”.  Many folks just raise animals, and many just
raise plants.  And human-based compost (“night soil”) has been blacklisted
for the moment. Of those of us who raise crops and livestock, few, if any,
are providing all their own fertility and feed needs.  Luckily, it’s easy
to find folks who have a barn they are happy to have cleaned, and I can
truck in load after load of horse, sheep, rabbit, cow, chicken...all sorts
of great poo.  I’ve trucked enough loads of manure that upon arrival, one
farmer exclaimed “it’s the Great Poo Guru!” (that’s a compliment to me).
Indeed, picking up poo is one of my favourite neighbourly activities.  But
it takes a lot of time and energy.  I truck by cows dropping manure right
there on the fields of other farms, and I marvel at the simple efficiency
of grazing livestock.  At a certain point, trucking manure no longer makes
sense.  Gas is expensive, pitchforks are small, and an unknown poo can
have any number of residual toxins.

Another organic option for adding animal manures are “granular” products:
composted and pelletized manure, bones, and blood from slaughterhouses,
and grease from dumpsters, among other things.  They are fairly cheap,
easy to handle, and potent. Of course, we are supposed to overlook the
inter-dependency we then have with large, industrial slaughterhouses and
food chains, as well as any toxins that can pass through their processing.
Some suggest we are doing a service by using wastes; others suggest that
the horrors of industrial meat production can only exist if organic
farmers keep buying those wastes.  Whatever floats your boat.  I say it’s
alright to use such products to build a farm, and while we should strive
for an ideal that moves beyond it, we should support evolving farmers
wherever they are.

When thinking about manures, I always return to that ideal farm, where
crop needs are met by animals and animal needs are met by crops. As I
haul loads of manure, I am well aware of the path that must be taken;
with each passing season it becomes clearer to me that I need to raise
more than chickens!  If there’s one thing I know, it’s that sometimes
you have to stop looking for what you want and just create it.

A mixture of manures, composts, and cover crops can increase soil
biodiversity and fertility.  What seems less utilized is a biodiversity of
plants (with the exception of cover cropping and pasturing) in order to
build healthy soils.  For instance, some say certain plants can root deep
into sub-soil, pull up nutrients, and distribute them into topsoil.  But
how many of us celebrate dandelions and docks, or encourage nettles and
comfrey?  Perhaps the answer to our reliance on industrial rock mining and
slaughterhouses lies, in part, in building relationships to these dynamic,
“bio-accumulating” plants.

A living soil needs sources (manures and plant residue), and it also needs
protection from toxins and tillage.   I feel little need to discuss the
dangers of using toxins when it comes to soils, but I do want to talk
about tillage.  In our vegetables, we are establishing semi-permanent
pathways of clovers and grasses that are mown instead of cultivated, and
can remain undisturbed for several seasons.  Even as we till the beds
where we plant, we are allowing these strips to (hopefully) become places
of respite for beneficial fungi and bacteria, which can then repopulate
the beds following tillage.  After several seasons the beds and pathways
can simply be switched.  This semi-permanent pathway system creates a
multi-year cover crop before a bed is integrated into a production
rotation.  I think it is a system for people with limited land (or rent
money) to have more cover crop and less tillage.  Additionally, to push us
to develop new ideas, roughly 1/10 of our production areas are hand-tool
based, no-till farming, where we are experimenting with vegetable and
grain production without the use of machines.  I call this kind of farming
“worm-till” farming to differentiate it from large-scale,
herbicide-intensive no-till systems.  “Earthworms make the best tillers,”
Susana Lien once told me.  And after seeing her farm (Salamander Springs,
near Berea) flourish on mountainous clay, I have to integrate that idea
with some sincerity.

Farming is simple and complex.  Simple in that farmers need only observe
and mimic nature as much as possible: be diverse, balance animals and
plants, cycle things endlessly, need few/no inputs, and always cover the
soil.  And yet farming is so complex!  No two farms are alike. Each farmer
has a different set of resources, every family a different level of needs,
and each farm a different relationship to a society that is changing with
lightning speed.  Farmers are jugglers, integrating broad biological
concepts and definitive economic and environmental realities with the
humilities of one plot of land.  I am convinced that there are no easy
answers in farming, only really good questions.  It is ultimately up to us
to move forward and incorporate the good questions.

Ultimately it is time that will bring us to a sustained, thriving farm
community.  Time farming.  Time living with a real dependence on our soil,
for income and sustenance. Time walking our fields in meditation and
observation; fertilizing with the proverbial “farmer’s footsteps”.  Time
adapting to the future. In time, we will do our best to pass on our
experiences, our questions, and our farms to a generation that can do the
same, and all along the way, things will continue to get right.