The Weather Detective by Peter Wohlleben

Author:Peter Wohlleben
Language: eng
Format: epub
Publisher: Penguin Publishing Group
Published: 2018-06-05T04:00:00+00:00

8

ASSESSING YOUR SOIL QUALITY

WHEN it comes to natural processes, only half of what’s happening takes place above ground. Recent research has shown that bacteria and other primitive species reside up to 6 miles below the surface. Two ten-thousandths of a gallon of groundwater can contain some hundred thousand minuscule life forms, and it is possible that the total mass of the subterranean creatures exceeds that of all the animals and plants of the earth’s surface.

Beneath the surface of your garden is a gigantic habitat, rich in species, which has yet to be properly explored. In fact, you consume some of it every day, in your tea or coffee. Countless minuscule organisms end up in your beverage along with the groundwater, even after being treated before it reaches your tap. But since they are not harmful to us, and are often even beneficial, their presence is nothing to worry about.

For your garden and your plants, it is only the topsoil, the uppermost layer, that is important. The quality of this soil layer—whether it is rich or poor in nutrients, and whether it retains water well or is arid—essentially depends on the bedrock. After all, it is only the underlying rock that is present locally that crumbles into soil through the process of weathering.

Weathering occurs over extremely long periods. In prehistoric times, the landscape would have consisted initially of bare rock. Severe fluctuations in the temperature left cracks in the rock, which water could penetrate. Winter frosts made the water freeze, thereby expanding and shattering large lumps of rock into small fragments. Chemical and biological processes formed acids that broke down the rock further until it was decomposed to the finest substrate. Physical forces, such as stormy winds kicking up sand in the air, worked on the rock like sandpaper, reducing boulders and stones to dust. The result is a layer of soil of varying depths, depending on the altitude. It also includes a good amount of humus, which we will discuss shortly.

So, the weathering of rocks results in small particles, and the size and composition of these are crucial for the fertility of the soil. We tend to categorize soil types into sand, with large grains, silt, which is finer, and clay, which is finer yet. With pure sandy soils, where you can feel the grains of sand, the layers of soil are loose and water drains through easily. Silty soils are considerably more compact, but still permeable to water. Clay soils, on the other hand, consist of very fine particles. These soil types retain moisture and hold very little air. A combination of all three types is called loam. This ideal soil mix retains water and nutrients, it is well-aerated, and, as long as there is sufficient humus, it makes for fertile growing conditions. But even with loam, there are differences in quality, depending on the rock type that forms the basis of the soil.

This process of soil formation continues to the present day, but it is happening much more slowly than in the prehistoric era.

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