The soil food web

I'm reading a fascinating little book at the moment called Teaming with Microbes: The Organic Gardener's Guide to the Soil Food Web, by Jeff Lowenfels and Wayne Lewis. It's all about the complex interrelationships between organisms in the soil and the plants in our gardens.

I learned for example that plants form partnerships with particular bacteria and fungi. The bacteria and fungi feed on carbohydrates manufactured by the plant (through photosynthesis) and exuded by its roots. In return, their excreta provide nitrogen and other nutrients to feed the plant, and they coat its roots in a protective film. Individual plants actually control which organisms they attract, according to their needs!

Then the keen gardener comes along with crude chemical fertilisers and knocks the whole system out of balance. No longer reliant on the microbes, plants grow fat on the readily available nitrates poured into the ground. The microbes consequently die out. From then on, the gardener has to keep feeding the plants artificially or they won't thrive – remember, the microbes are gone.

When the microbes leave, the larger soil organisms such as earthworms leave, to the great detriment of soil structure and soil health. As the soil structure degrades, more and more of the synthetic fertiliser goes straight through into the groundwater, where it becomes an environmental pollutant.

(As an aside: ever wondered why we have toxic algal blooms in our rivers every summer? Yeah, right, it's 'natural'.)

With unbalanced nutrition, the plant is more susceptible to pest and disease attack. What to do? Spray it with various '-icides' to rectify the problem. Trouble is, they make the soil an even less hospitable environment for its natural inhabitants.

In other words, a quick fix solution has put the gardener on a chemical tread mill. From now on, gardening will be more labour intensive and expensive. It will rely on inputs which can't be manufactured within the garden, but are products of the petrochemical industry.

To my mind, it's just one more example of how organic methods are not just more effective than chemical methods, but easier and cheaper.

Perma-thoughts, 2

Here's an example of how my Permaculture course has changed my perspective on elements of the Patch:

On the northern boundary we're establishing a windbreak against hot, drying winds. At the moment, this consists of 15 Flinders Ranges wattle saplings. All but one are doing well, and should start to be effective in the next 24-36 months. I was quite pleased with this idea when I first thought of it: 'Good idea to create a microclimate, Steve!' I thought.

Will eventually be a windbreak: 15 tiny wattle seedlings , Aug 2011

Now, applying some Permaculture principles, I can see ways to make it a whole lot better:

Principle: Build diverse, stable ecosystems.

OK, a 15 x 2 metre windbreak (eventual mature size) isn't exactly an ecosystem. But what if I planted sheokes on the leeward side of the wattles, and grew a small-leafed (because not rampant) hardenbergia up the sheokes when established, and dug a swale to catch water runoff, and sowed the bank of the swale with dichondra and native violets, and planted blueberries in the lee of the windbreak? And put logs in the swale to provide habitat for lizards and amphibians?

Would this be an ecosystem, or just a collection of plants and landscape features? Let's have a look:

The wattles and the sheokes together will make a more effective windbreak; both are nitrogen fixing. When they are cut back (mulch for the veg beds), some of their root mass will also die off, making nitrogen available to the soil. Hardenbergia is also nitrogen fixing, so we have three plant species improving the soil. Blueberries on the leeward fringe of the windbreak will benefit from the added nitrogen, and also the acidic environment provided by the mulch of sheoke needles.

All of these are flowering plants and will provide forage for bees and nectar-eating birds. In addition the swale should become an ephemeral wetland, attracting the numerous frogs from the surrounding area - we're lucky to have two established wetlands to the northeast and northwest of the site.

So this begins to look like a functioning ecosystem, with beneficial interactions between the various species. In time further species would be introduced (or colonise by themselves) and it would become more diverse.

Principle: Every element of a design should function in many ways.

This is also referred to as 'stacking' functions. How does our windbreak fit in with this?

As envisaged above, it now serves the following functions:

• reduces the impact of hot, drying winds
• provides mulch for veg beds
• provides forage for bees (pollinators, suppliers of honey)
• provides habitat for insectivorous birds, reptiles and amphibians (pest control)
• provides fruit
• improves soil nitrogen
• improves water infiltration
• removes the need for mowing (saves labour)

Now, not all aspects of the plan will turn out as envisaged. For example, it may be that blueberries just won't flourish where I want them, so I would have to use other berries. That would tie in with other Permaculture principles:

Apply self-regulation and accept feedback.
Use small and slow solutions. (Otherwise referred to as incremental design.)
Creatively use and respond to change.