We all know soil is important. Even though we often take it for granted we know that good soil in your garden is crucial to planting success. By deconstructing the basic elements that make ‘good’ soil we might better understand the importance of sustaining this vital resource for both your garden and the wider environment.
Let’s start from the beginning; soil has four basic components:
1: Rock particles. Over many thousands of years, soil particles are formed from rock fragments eroded from a variety of means, including glaciation, river formation and weathering, and deposited on the surface. These range from the finest soils, clays, to the largest, sand. The soil particles contain valuable minerals which are dissolved and are contained in the second component, water.
2: Water. Without water soil is dry and inert. Water held in the soil might best be called ‘soil water’. It’s like a soup that holds dissolved minerals that are essential to plant development. Through the action of drainage, the soil water moves through the soil. In Nature this encourages roots to ‘follow’ and assist in growing and anchoring plants in the soil. This movement is driven by gravity and the rate of movement is governed, in part, by the relative amount of the third component, air.
3: Air. Air in soil (’soil air’ or ‘soil gases’) contains a mixture of gases chiefly comprising nitrogen, carbon dioxide and oxygen. Interestingly, about half the mass of soil is made up from a combination of soil air and soil water. Crucial chemical and biological actions take place within the cavities in the soil so a well-aerated soil is essential in your garden. The final component is arguably the most important although it makes up the smallest proportion of soil. This component is organic matter.
4: Organic material and organic matter. Organic material or matter comprises animal and plant remains in varying degrees of decomposition. Organic material also includes the microbes, insects and animals that live in soil. In Nature organic material is deposited on land over time. As it decomposes essential nutrients are released into soil which serves to sustain soil fertility and condition. Organic material that has completely decomposed is known as humus. This is a stable component in the soil that can justly be referred to as organic matter. Crucially, as organic material (in all its forms) deposits its waste or decomposes vital elements to plant development including nitrogen, phosphorus and potassium are released into the soil. A fertile soil contains only about 5% organic material but is by far the most important component in sustaining soil condition and fertility.
The physical, chemical and biological integrity of your soil is directly linked to the quantity and quality of the organic material that is added on to and into your soil.
Quick facts and tips:
-Fertilizer is useful in the short term (a matter of weeks) but is a poor substitute for good soil.
-Organically rich soil is a natural means of storing carbon in the soil. You can help the environment by using organic material to act as a carbon sink. Don’t forget to tell your neighbours!
-Adding organic matter to your soil allows your plants to thrive. By so doing they absorb more carbon dioxide through photosynthesis and emit more of the life-enhancing gas, oxygen, through cellular respiration (through the underside of leaves).
-Avoid leaving your soil exposed to weathering and run-off. Mulching with organic material helps lock-in essential minerals and nutrients.
-Avoid excessive cultivation of your soil. This damages soil structure, releases otherwise locked-in greenhouse gases like carbon dioxide and methane. Cultivating too vigorously can also damage plant roots and disrupt complex and beneficial microbial activity.