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.

The Patch update

It's been a little over six months since Susan and I started work on the Patch - our Landshare garden at Jill's and Mike's place. Here's a pictorial update on how things are going.

June 2011

December 2011

All in all, we're pretty pleased with the transformation from former horse paddock to productive vegie garden. The main problem was that I was away in Europe for the critical period mid-September to end October. Won't do that again.

Potato bed

Potato bed

The potato bed has produced a good crop of Pontiacs and the Dutch Creams are still going strong. This bed hasn't been watered since September and yet it's full of lovely, moist, worm-filled humus made from seagrass, mushroom compost, pea straw and home-made compost.
A second batch of Pontiacs has just been planted out and covered with compost made on site. The pea straw bales are breaking down quite fast (with the help of some hungry mice) - by the end of the summer I think some will just be shapeless mounds of straw.

Grain bed (not!)

Amaranth

The next bed was intended as a grain and pulse bed: amaranth, chia, quinoa, chickpea and linseed were sown in November. This was an experiment as I thought conditions might already be too warm, at least for the quinoa and chia. Looks like I was right: only the amaranth came up in worthwhile numbers, with a few chickpeas. An additional problem was watering: with only one or two visits a week and only hand watering, it was impossible to keep the seed bed moist. Lesson learned: any sowing of fine seed needs to coincide with decent rain. We got a nice crop of self-sown mallow, though!
I'm trying again with sunflowers, having enriched the soil with our home-made compost. Unenriched parts of the bed will be used for buckwheat and another green manure crop.

Watermelon and solanum bed

Eggplants, capsicums and watermelons

I divided this bed in half for ease of access - all watering at the Patch is by hand with a watering can. After a green manure crop, this bed was further enriched by the addition of 1.5 m3 of mushroom compost: I'm aiming for a rich, moisture-retentive soil. I think I walked 20 km with that wheelbarrow, as it's a couple of hundred metres from the driveway to the Patch.
Two rows of eggplants will hopefully provide shade for watermelon foliage and roots in hot weather.
I've never grown watermelons before but thought I would give them a try in this sunny position. I'm fairly sure we won't be short of eggplants come autumn - 16 plants may have been slight overkill. Not sure what else I'm going to put in here, possibly some autumn brassicas or leeks.

Three Sisters bed

Three Sisters: maize, beans, pumpkin

The Three Sisters system of symbiotic cultivation comes from South America: maize, climbing beans and cucurbits (in this case, Anna Schwartz pumpkin) are grown together. The beans enrich the soil with nitrogen and bind together the maize stalks, preventing wind damage; the large cucurbit leaves shade the soil, helping to keep it moist for the maize; the maize provides a frame for the beans to climb up. I've been sowing the maize in 1-metre blocks every 2-3 weeks and 4-5 beans a metre on the south side of the blocks.

Then there's a row of capsicums which were left over seedlings from our other garden. I guess they'll have to be the fourth sister.

Lucerne and wildflower strip

Lucerne and wildflower strip - decorative and useful

This 20 x 1 metre strip of lucerne interspersed with Queen Anne's Lace and California poppies has turned out really well. So much so that I've decided to make it 2 metres wide in the autumn. The flowers attract beneficial insects and the lucerne will provide mulch for the vegie beds. Looks great, too.
This bed hasn't been watered since early September.

Comfrey strip

Comfrey (Bocking 14)

20 comfrey plants were planted in a 20-metre strip back in July. All are doing well. I try to give them some supplementary water in hot weather, but they largely fend for themselves. I chose the non-weedy Bocking 14 variety from Diggers Club.

People have been puzzled why I'm producing semi-industrial quantities of comfrey. It mines the subsoil for minerals, then makes these available as its leaves break down. It's great as a compost activator, as a soil-enriching mulch and as comfrey tea (now brewing) - a nutritious but extremely smelly liquid fertiliser. The flowers will be good for bees (when we get some, but that's another story), and I see ladybirds and assassin bugs hanging out around them too.

Compost bays

Next batch of green stuff ready for composting

The four-bay compost system (such opulence! such luxury!) was built from old timber from Jill's and Mike's woodshed. It's working really well, but had to be lined with heavy-duty weedmat and old carpet, as the thuggish kikuyu grass from the neighbouring school oval was determined to get in on the act.

Lovely compost - once was weeds, cardboard and chook poo

We've just produced and used our first batch of lovely crumbly compost using the cold-composting method. Now the blanket weed I dug up in July is being hot-composted. Despite dire mutterings from locals about the stuff being indestructible, this is going a treat. If it once lived, you can compost it.

That's about it for now. I'm hoping a Permaculture Design Certificate in February will give me some more inspiration. Also we're doing a bee-keeping course in April as we think our Patch is a bit of a bee-desert, being surrounded mostly by acres of well-mown grass. If we want pollination, we'll have to provide the pollinators and plenty of bee tucker.

Happy New Year and happy gardening in 2012!

Soil

For the past couple of years I've been paying more attention to the soil in my garden – 'soil' is a short word, but what is it exactly?

Soil is an amalgam of tiny particles of rock with humus (decayed vegetable matter), fungi and bacteria. This provides a substrate for plants to anchor themselves in and a sponge to capture water, making it available to the plants' roots.

Soil contains a wide variety of nutrients which are essential to healthy plant growth, including the big three – potassium, nitrogen and phosphorus. Then there are the secondary nutrients calcium, magnesium and sulphur. Thirdly, there's a range of micronutrients: boron, copper, iron, zinc, chloride, molybdenum and manganese. 'Micro' because they are only present (and needed) in tiny quantities. They're also called 'trace elements'.

So far, so complicated. But we're not done yet. Not only do plants need all these nutrients in varying quantities, it appears that they also need the help of a type of fungus to enable them to digest their food. This symbiotic relationship is called mycorrhizal (fungus and root).

So there's a lot more to 'soil' than just some brown crumbly stuff. But how can I apply this knowledge practically in the garden?

Well, I monitor soil pH (acidity/alkalinity), because I know that it affects a plant's ability to take up nutrients. A pH test kit is quite cheap and easy to use. An excessively acidic (under 5.5) or alkaline (over 7.5) soil can be corrected by the addition of lime or sulphur respectively. I check the soil pH about once a year.

Other than measuring pH, soil care is fairly unscientific in my garden. I adopt a variety of approaches, hoping that they will all help.

• I try to get as much organic matter into the soil as possible, through the use of green manure (a crop which is grown, slashed down and dug in to feed the soil) and home-made and bought-in compost.
• I boost micronutrients through the addition of rock dust.
• Now that my worm farm is flourishing I can also add worm castings and worm 'wee' to the soil, hopefully boosting its population of beneficial bacteria.
• The organic mulches I apply, such as lucerne and pea straw, protect soil microbes and plant roots from overheating and desiccation, and add some carbon and nitrogen as they break down.
• I try to avoid deep digging, which brings sterile subsoil to the surface.
• I'm experimenting with the use of comfrey and lucerne - deep-rooted perennials - to recover lost nutrients from the subsoil.
• I don't sieve soil unless absolutely necessary, because it disrupts the soil structure and can produce a hydrophobic surface.
• I'm very careful about what I put in and on my garden soil. No detergents, no poisons like glyphosate (Roundup or Zero), which may harm beneficial bacteria.

As well as these basic measures, I've recently started to experiment with two new products which have come on the market: biochar and Bactivate, a bacterial fertiliser.

Biochar is the 'black earth' that is supposed to have given the naturally poor Amazonian soils great fertility, supporting intensive agriculture in pre-Columbian times. Basically it's charcoal, in a form which binds water and nutrients, making them available to plants and improving soil structure. Bactivate is also carbon based: it's pellets of coal dust coated with beneficial soil bacteria.

By the use of all these methods, I'm hoping to transform the rather poor, sandy and hydrophobic soil I inherited for my vegie patch into a rich, fertile growing medium. Comparison with other parts of the garden suggests that I've already made quite a bit of progress.

What I'd really like is the rich, dark soil of my mum's and stepdad's garden in western France. Come spring, the vegies in the Limousin leap out of the ground at an astonishing rate. However, it's taken probably 3,000 years of organic cultivation to make that soil, so I may have a way to go yet!