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Posts Tagged ‘topsoil’

Each garden has its own personality, distinct oddities that make it unlike any other patch of ground in the world. My current garden amuses itself by sending me a mystery vine every summer. It’s always in a different spot, it’s always something from the squash family, and it’s never the same species.

One year enormous yellow flowers turned into hard green balls which slowly resolved into pumpkins. Another year, the vine climbed around a wire bin in the shady northeast corner of my garden and by season’s end dripped with tiny jewel-like decorative gourds.

Two summers ago, as I awaited the huge sexy flowers typical of squashes and gourds, I was startled by spikes of white flowers poking out along my vine: it was a wild cucumber.

Last year, however, I could find nothing. June came and went. Maybe I missed some offering to the garden gnomes. But then, in mid-July I saw it beginning to creep along between the house and the garage. Just before the leaves dissolved into black mush this fall, I harvested two perfect acorn squash. Last night I baked them for dinner with apples and a touch of butter and brown sugar.

I had not left space for this squash (it grew into a path and we stepped over it all summer), I had not purchased the seed, I had not planted the vine, nor had I watered or weeded. The squash, all on its own, planted itself, harvested its own sunlight and extracted its share of limited rainfall. It was free in every sense of the word: no labor, no money, no planning, no time.

But, least you think that the “no free lunch” adage applies only to lunch, I have to tell you it applies to dinner too. It turns out there was a cost to my squash. It goes by the eye-glazing name of soil depletion. The squash took from the soil the nutrients it needed to grow–nutrients that will be gone from this patch of land for years to come unless someone returns them, perhaps via a handful of compost or some chicken droppings.

In the words of Lester Brown, founder of the Earth Policy Institute, “The thin layer of topsoil that covers the planet’s land surface is the foundation of civilization.” Looking back on world history is more often than not a study of soil productivity. Where soils were deep and life-giving, people flourished, when soils were over-tapped and over-grazed, civilizations fell.

Indeed, when we consider what is necessary to support life on earth, productive soil is right up there near the top of the list, close to sunshine and water.

Healthy soil is a world unto itself: a mix of minerals, organic matter, insects, bacteria, fungi, and animals, that provides both the critical nutrients plants require as well access to water and air.

Soil formation begins with a pocket of minerals such as sand, glacial grit, or lava, worn fine enough for a rugged pioneer plant to sneak in a few roots. When the plant dies it returns some of the nutrients it used as well as adding organic matter. As the soil becomes richer, more plant species are able to survive.

Insects and animals appear, contributing their droppings and eventually their bodies to the gradually deepening soils. Its a beautiful natural process, but unfortunately rather slow: a single inch of topsoil is approximately five hundred years in the making.

The planet is now losing topsoil 10-20 times faster than it is being replenished. Much of this erosion is due to farming and grazing practices that leave bare soils exposed to wind and rain.

As topsoils are washed into our waterways and blown into dust storms, so are vast quantities of carbon released. Scientists estimate that there is three times more carbon locked in soil than there is currently in the atmosphere. This carbon is released as soils are disturbed, and may contribute up to 30% to global warming.

If there were vast swaths of untapped agricultural land just waiting in the wings, none of this might be a problem. But farmland is in scarce supply in many places. A few years ago South Korea tried to purchase a 99 year lease to half of Madagascar’s arable land. South Korea and Madagascar are 6,500 miles apart.

Virtually all human food calories come from the land. Global food production has kept pace with population growth largely because of reliance on chemical fertilizers. However, overuse of fertilizer, along with many other modern farming practices eventually destroy soil structure and the soil ecosystems that maintain it. The result is that food production per acre of land is declining.

Although most people pay no attention to it, good dirt is a resource sorely in need of protection. Practices that protect soil fertility, soil structure, and retain soil carbon include low or no-till methods, leaving some of the crop behind after harvest to hold soil in place, and planting cover crops, windbreaks, and vegetative buffers along waterways.

On my quarter acre square of the planet, I try to minimize the amount of organic matter that leaves our property. We compost our food scraps, pile up our oak leaves, and allow our grass clippings to disappear back into the lawn.

The area where my acorn squash grew used to be a compacted beat up piece of grass. A few years ago I put down a thick layer of partially decomposed oak leaves to kill the grass, and topped it with pine needles swept up from Brunswick streets. The result was a lovely rusty golden path between the structures, edged with a few ferns, and other plants–and no need for mowing. It was here that my squash chose to grow, perhaps a thank you for giving something back to the soils.

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