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Part 2: The answer lies in the soil
Part 2: The answer lies in the soil
9 February 2015,
by Kate Harries
The more we learn about the natural world, the more we find out about its elegant solutions to problems we labour clumsily to address. Thus it is that unimaginable zillions of organisms in the soil decompose organic matter, sequester carbon and nitrogen, promote porosity and aggregation, prevent erosion, purify water and create fertility.
In Part 1, I wrote about these creatures that make up our “micro-herds” of hidden helpers. In our ignorance, we gardeners and growers disrupt their processes, exhausting both ourselves and the soil. How do we do this?
Machinery, as well as human or animal foot traffic, leads to compaction. Soils are most vulnerable when they are wet. Compaction destroys the soil’s delicate structure, decreases its ability to absorb moisture, pollutes waterways by increasing runoff, starves micro-organism populations and increases greenhouse gas emissions. For gardeners, the lesson is, work from the side of your beds, stay on the paths.
. The soil’s flora and fauna are organized into very specialized and inter-connected communities, the majority living within a couple of inches of the surface, but a large proportion to be found in the “rhizosphere,” the area around the plants’ roots, which exude proteins, sugars and carbohydrates to attract microbes and fungi that will help the plants absorb nutrients. The micro-communities in the soil aren’t layered so much as “nested,” with multiple interconnections up and down and sideways, between decomposer and recycler, predator and prey. When we dig or till, we wrench the specialists away from their appointed tasks into environments where they can no longer serve or even survive – and it takes precious time and energy for these communities to rebuild.
Synthetic fertilizers and pesticides destroy the natural balances in the soil.Here’s how Toby Hemenway describes chemical fertilization in his book
Gaia’s Garden, A Guide to Home-Scale Permaculture:
“The soil life roars into a feeding frenzy, spurred by the more than ample nitrogen, phosphorus, and potassium in typical NPK fertilizers. Since organisms need about 20 parts carbon for every one of nitrogen, it isn’t long before any available carbon is pulled from the soil’s organic matter and tied up in living bodies. These organisms exhale carbon dioxide, so a proportion of carbon is lost with each generation. First the easily digestible organic matter is eaten, then, more slowly, the humus. Eventually, nearly all the soil’s carbon is gone, and the soil life, starved of this essential food, begin to die… With important links missing, the soil life falls far out of balance. Natural predators begin to die off, so some of their prey organisms, no longer kept in check in this torn food web, surge in numbers and become pests. Sadly, many of the creatures that remain after this mineral overdose are those that have learned to survive on the one remaining source of carbon: your plants. Burning carbon out of the soil with chemical fertilizers can actually select for disease organisms. All manner of chomping, sucking, mildewing, blackening, spotting horrors descend on the vegetation.” Next step? Sprays and the gardener locked into a chemical treadmill. “It’s a losing battle,” Hemenway notes, “reflected in the fact that we use 20 times the pesticides we did 50 years ago, yet crop losses to insects and disease have actually increased.”
Let us avert our eyes from this dismal prospect and consider humus. (No, not hummus, that’s the chickpea dip.) Humus, pronounced hyoumus, is a relatively stable form of carbon produced when organic matter breaks down. It’s critical to soil health and can persist for hundreds of years if protected by aggregates of soil particles. But if the soil is broken up by you-know-who, the humus will decompose, release CO2 to the atmosphere and be exhausted in a decade or so.
Your mission as a gardener and steward of your outdoor space is to make and preserve humus.
Step 1 is mulch. Mulching is also Step 2 and 3. In fact, mulch is everything. Don’t plant anything without it! It preserves moisture and moderates temperature, and as it breaks down, it feeds the organisms and thus your plants. It discourages weeds, and is a slow form of composting, favoured by permaculturalists, who actually frown on “hot” composting methods.
An explanation: The traditional compost heap is put together quickly with layers of different material (grass clippings, kitchen waste, manure, sawdust, straw) to achieve the ideal 30:1 carbon-to-nitrogen ratio. The micro-organisms multiply, give off heat, break down the organics, and if the heap’s outer layers are turned in when the heat starts to subside, the process reactivates to ensure full decomposition. In summer, a well-tended pile can be turned into compost in less than a month
Here’s Hemenway again, on why he doesn’t think compost piles are the best way to raise micro-herds. “Whenever I turn or move my compost pile, I know I’m murdering millions of these wonderful helpers, smashing their homes, bludgeoning them and their children with my spading fork, desiccating all those who end up on the outer layer of the pile.” Aieeee!
So Hemenway prefers to minimize disruption to the ecological succession that takes place in the soil. He like cool composting piles, and he likes sheet mulching even better – a layer of newspaper or cardboard topped with organic material like straw, leaves, ground bark, woodchips, up to a foot deep. Composting can take place within the mulch – put the garden waste to decompose right where it’s needed on top of or under the mulch, the kitchen waste too if you don’t have animals that will dig it out. A confession: I will continue to maintain compost bins (with a twinge of guilt for my murdering ways) because I have dogs that might dig up my kitchen scraps and because I need to make large amounts for potting mixes.
< A foot of mulch is intense, but everyone should be able to build their mulch layer to three inches or so, and their soil will benefit.
A thought: Many of our native bee species (that we need for pollination) are ground-nesters and require bare soil. And butterflies like mud puddles, and barn swallows and other birds use mud for nest-building. So don’t go all out. Think diversity of habitat. Keep some patches free of mulch and vegetation – in the sun, for the bees, and in the damp, for mudlovers.
A word about living compost. The commercial stuff has been sterilized to kill off disease and weed seeds. That kills the micro-organisms too. Compost from a bag is at best inert dirt, at worst may contain residues of pesticide or heavy metals. It does have its uses, but if you want to use compost to add life to your soil, make your own, or obtain some made locally, so its biology is suitable for your area.
I have been working in recent years on giving up a habit that’s hard to shake: Digging. I used to believe that the summit of achievement in preparing a vegetable patch was triple digging – which involved digging three layers down, moving each layer over one square at a time and mixing in compost and other amendments along the way. Backbreaking work. I didn’t do it often, but felt maybe I should. Now we know that we can let the micro-herds do it all for us.
Next - Part 3: The latest fads, the best buys for soil nurture
In the first version of this column, I stated that compost purchased in bulk from Simcoe County’s waste transfer stations is processed in Hamilton. A reader emailed me that I had it wrong:
The Simcoe County transfer station here in Alliston is used solely for leaf litter, brush/twigs, straw bales, and misc. outdoor garden waste. There is no objectionable odor associated with this operation and the finished product “compost” is sold locally each spring. The leaf litter compost is likely missing much of the desirable “
microbes and fungi” associated with natural leaf mold decomposition. Commercial operations turn the large piles, introducing nitrogen / oxygen which in turn creates heat. Other than the small bits of road side plastic and metal, it still makes for a good soil conditioner. Most people don’t give much thought to the soil. You’re doing your part educating those willing to listen. Even I need to be reminded once in a while. Thanks for sharing.
Thank you, dear reader, for putting me straight! I checked with the County of Simcoe and they confirmed that yard waste is collected from across the county, composted to a high heat at the closed New Tec transfer station so as to kill off weed seeds and pathogens, and distributed back for us to purchase in the spring - which makes it live and local. I’m happy to hear this, because I do use it. KH
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