Ecological Pest Control I: Soil Biodiversity

Where We Have Been:

In Organic Pest Control III: Acts of Gardening Violence, Petty and Profound, I suggested a conceptual framework for organic pest control based on the notion that labor intensive interventions are ecologically harmful.  This  framework is intended to help organic ecosystem-ers decide when, whether and how to deploy ecological, mechanical, and chemical pest interventions in a selective rather than reactive manner, based upon the peculiar ecologies in which they are working, and based upon their gardening goals and personal resources.

We will explore each intervention — ecological, mechanical, and chemical — in more detail as we progress over the next several installments.  I want to begin with ecological intervention, the very chassis of organic pest control.

The Ecological Tool Kit vs. “Cultural Controls”

I couldn’t agree more with the old-timey adage that an ounce of ecological pest prevention is worth a pound of mechanical or chemical cure.  However, the ecological approach is substantially different from the “cultural controls” approach to pest prevention commonly found in  most gardening books.  The “cultural controls” approach generally teaches us to:

Cultural Spoof

Memes about “effortless” organic gardening give me hives. Organic gardening is hard work.  It’s  time somebody told  the sho’ nuff truth, so I went  ahead and spilled the beans.

  • test our soil (in different ways) and to “correct” its deficiencies using amendments;
  • work in plenty of well-rotted organic matter;
  • choose the appropriate plant for the appropriate location;
  • space plants properly to ensure good air circulation;
  • select disease resistant cultivars and seeds;
  •  water deeply, and early in the day whenever possible;
  • keep the garden and our tools hygienic;

…and the like.

The “cultural control” approach has always made me … uneasy… though it took me several years to figure out why.  It assumes that the gardener is the main (the sole?) actor in the garden with power over pest and disease proliferation, an idea that is categorically and demonstrably untrue.

Ecological pest interventions are different from cultural controls because they de-emphasize the small number of cultural adjustments that the human being can bring to bear on the garden.  They insist that the ecosystem is an agent of its own well-being.  The gardener is ONLY ONE organism acting within a greater system, and in the long-run we are the least powerful.  For that reason, it is in our best interest to enable the other ten thousand garden actors – named and unnamed – to do work that we, ourselves,  manage  with the finesse of a bull in a china shop.

A functioning ecosystem with maximum biodiversity is the least labor intensive, least agriculturally violent pest control system in the organic gardener’s tool kit.  The question is how to  “invite” the ten thousand named and unnamed gardeners into our backyards?  It’s a Field of Dreams sort of thing: if we (re)establish and support the garden’s infrastructure, then pest and  disease prevention will come.  Soil biodiversity and hedgerow biodiversity are the garden’s critical infrastructure.

I will take up the subject of hedgerow biodiversity and pest prevention in later posts.  For now, let us consider how we might (re)conceive and encourage biodiversity where we need it most but remember it least:  in the bacterial and fungal communities right beneath our feet.


Building Soil Biodiversity

Plow agriculture is arguably the earliest catastrophically violent mechanical farming intervention practiced by human beings.  Contemporary plowing, roto-tilling and double-digging techniques are descendents of this ancient agricultural practice invented  in the 6th millennium BCE.  Think about it: “good cultural practice” dogma regarding soil preparation is a relic from historical times, places, ecologies, technologies and crop varieties that may be – but more likely are in no way – related to those facing the 21st century gardener.

Brace yourself now, because here it comes, straight from the hip.  If you are really serious about soil health (and face it, what organic gardener isn’t?) … if your mantra is ‘improve the soil,’ ‘feed the soil,’ ‘conserve the soil,’ & etc.,  then the one thing you must teach yourself is not to dig in it.  Straight up, folks: leave. your soil. alone.

Do Not Disturb

Plowing, tilling, and double-digging are usually explained as necessary techniques to break up, aerate and improve the tilth of heavy or compacted soils; they are supposed to suppress weed competition, turn under and break down crop residue, and disrupt the life-cycle of over-wintering pests.  What they really do is:

1)   impair a local soil’s ability to sequester water in a normal way, causing it to desiccate;

2)   impair a local soil’s ability to drain in a normal way causing rapid run-off, and therefore soil erosion;

3)   enable rain to run-off rapidly, carrying phosphate and soluble nitrogen into the waterways, thereby depleting the soil of needed plant fertilizer and polluting our waterways;

4)   disrupt the microscopic microbial and fungal communities living in soil that feed, water, fertilize and inoculate plants against diseases.

Click here for an excellent film series on the consequences of inappropriately deployed plow agriculture in the American case.

Click here for an excellent account with film footage of the consequences of inappropriately deployed plow agriculture in the Soviet case.

Soil is a complex and very delicate matrix where inorganic and organic molecules meet, interact, and nurture life.  Miles and miles of microscopic fungi forge mycorrhizal connections between the inanimate world of stone and the animate world of plants and animals.

Why is this important?

It turns out that some plants are pretty inefficient at absorbing water directly through their roots.  Many other plants are downright poor at absorbing inorganic molecules like  nitrogen and phosphorous from the soil.  Nitrogen fosters new cell growth in plants, and phosphorous is responsible for root growth and reproduction.  When these are in short supply plants weaken and become extremely susceptible to pest pressure.

Do Not Disturb

Lucky for plants, mycorrhizal fungi are brilliant at absorbing water, and share it with the plants with which they live symbiotically.   They are also brilliant at sequestering, and sharing, inorganic compounds like phosphorous and nitrogen.  Some mycorrhizal fungi even destroy competing fungal spores that cause plant disease.

In return, plants provide microscopic fungi with the complex carbohydrates (sugars)  produced in their leaves during photosynthesis.  Get this: more than half of the vascular plants on earth evolved as mycorrhizal symbiotic feeders.  Furthermore, nearly 80% of human food crops are mycorrhyzae symbiotes.  The plow, the roto-tiller, the shovel disturb the very feeding system nature put in place to insure plants are thoroughly fertilized, and watered.

Soils with perfect tilth, porosity and fertility are laid down and built by biological processes taking place in the soil over time.  They can’t be laboriously tilled into existence.  Disturbing the soil interrupts the natural relationships and processes that take place between plant roots, subterranean insects, worms, microbes and fungi.  If we want soil communities to improve our soil, we must do what we can to stop disrupting their work.

“Is Sho’ Nuff telling us not to plow, roto-till, double-dig, or weed our gardens?”

Ummm…  Not entirely… but mostly yes.


“You can’t grow vegetables around here,” sez my neighbor. “It’s pure clay.” Gee, those look like potatoes. Gee, that soil is black gold. And no, I didn’t roto-till it.

Why the equivocation?

My purpose is not simply to discredit ecologically violent soil preparation techniques (you will certainly encounter strict “no till gardeners” but I do not count myself among them).  It is my opinion that plowing, roto-tilling and double-digging have a limited place in the organic gardener’s bag of mechanical tricks.  They are, however, ecologically violent practices deployed far too often for the sake of  illusory ‘efficiency’ at best, and as a reflexive cultural habit at worst.    My aim is to enable gardeners to question the appropriateness of these techniques for their particular ecosystems and in specific instances.

I am no one’s ecosystem guru except my own.   My backyard  is a typical ¼ acre slice of mid-western suburban development lot: chemically fed sod overlaying a bulldozer compacted, slippery, gray clay base.  The only obvious life in this soil when I first began cultivating it 12 years ago, were slugs the size of Cuban cigars, and 2 or 3 Japanese Beetle grubs per square foot of lawn.  I did not encounter a single earthworm here for upwards of 18 months.

“You can’t grow vegetables around here,” warned my next-door neighbor.  “It’s pure clay.”

Clearly, this ecosystem had suffered profound disruptions before I came to live here.  I suppose that if I had owned a big enough roto-tiller when I first started cultivating the property…  if I had had the means to rent and transport a big enough roto-tiller, if the gate in the fence had been big enough to accommodate a large roto-tiller… if I had the physical strength to wield such a tool myself…if, if, if… then surely I would have established this garden’s first beds by mechanically breaking open the soil.  Surely that bit of  mechanical intervention would have been no worse than the disease(s) already afflicting the property.

I garden without roto-tilling, without double-digging, and with very little time spent weeding (my garden has lots of weeds).   Instead, I choose, on a case by case basis, soil management techniques that do not rupture the skin of the earth: sometimes I:  smother, mulch, burn, top-dress, compost and mound-build.  Rarely, I pull a weed up by its roots.  More commonly, I cut a weed down to its roots.  I let leaves rot where they fall.

Do Not DisturbHow can we alter our garden practice in ways that will enable the uninterrupted unfolding of normal biological and hydrological processes beneath our feet?  We can dig less and observe our soil more.  We can think hard and honestly about our real needs.  We can factor the ecological violence of  soil-management into our organic pest-prevention calculus.  We can beware of applying “default,” “routine,” or “customary” gardening practices to every situation   We can choose from a broad range of gentler soil preparation techniques that will preserve soil structure and foster the soil biodiversity needed to maximize plant and garden health.

Next on Ecological Pest Control:

  • learn why weeds + weed tolerance = soil biodiversity!
  • expand your minimally violent soil management repertoire!

Stay Tuned for Upcoming Installments on:

  • hedgerow biodiversity
  • the mechanical pest control tool kit
  • the chemical pest control tool kit

8 thoughts on “Ecological Pest Control I: Soil Biodiversity

  1. Wow! OK, I have, in fact, heard about no-till and due to my inability to operate heavy equipment (other than a broadfork), I haven’t done much in the way of organized soil disturbing in the existing beds. That said, you have really laid out the reasoning to support my eco-healthy, back-friendly system and I thank you for that. 😉 PS, if poultry “aerate” the ground, does that count?

    • Sho'Nuff says:

      Bird activity in the garden is exactly the amount of cultivation needed for healthy soil. They’re eating your pests and weed seeds… while adding generously to the fertility of the soil. I’ll be adding a bit on keeping poultry when I cover hedgerow biodiversity. I have arthritis in my back. When I say we have to make choices that take into consideration our “resources” I mean our physical limitations, our time limitations, and the reality of our financial lives in addition to the ecosystems we are working with. Kudos to you!

      • We are very much on the same page, methinks. I want to post something soon about the progress of my tomatoes & give you a little shout-out. They are out-of-control happy…thx for the tips!!!

      • Sho'Nuff says:

        I’m so glad to hear that your tomatoes are doing well. Be sure to take pics so we can all see!

  2. someday4 says:

    This is just BRILLIANT!

  3. Lrong says:

    Am lucky that I can pick the pests by hand to feed my two chickens… they get some protein and my plants get some relief from the attacks…

    • Sho'Nuff says:

      I keep four chickens for this purpose too. They eat Japanese beetles up just like they are popcorn! When I talk about hedgerow biodiversity in my next post, I will suggest that people who are able to do so keep chickens. They are great for the garden. It is important to note that when I talk about “pests” I include fungal, bacterial, and viral diseases that are very hard to cure. Bugs aren’t really the worst problems that gardeners have to deal with. I’m glad to hear that gardening in Japan is so easy and pleasant. I am growing Japanese pumpkin this year. They are doing VERY well. I’m looking forward to eating nice pumpkin and making pumpkin filled mochi in the fall. Thank you so much for following my blog. Your cheery comments always make me smile.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s