Soil is the upper layer of the Earth's surface. It is made from organic material, minerals and small living forms. Soil is significant in two main ways in sustainable development - as the basis of agriculture, the living substrate on which crops are grown, and as a building and insulating material. It is also significant as a source of healthy homegrown gardens, safety of living environments (non-erosion, embankments, etc.) and as one of the important nature-based services underpinning urban and other human built environments.
Soil in agriculture
Soil consists of eroded rock particles (notably sand, silt and clay), organic matter (humus). and a wide range of organisms, including earthworms, bacteria and fungi. The soil category on Appropedia focuses on this aspect.
Complexity of soil
The soil, be it of the desert, forest or the swamp, is a mixture of the result of the weathering of rocks, the mineral substrate, and an almost infinite complex of microorganisms in a bewildering series of interacting ecosystems. The soil microbiota may be considered as the basic flora and fauna of this planet since every living thing on Earth's land depends directly or indirectly on the health of Earth's soil microbiota. The sea has a similar situation.
Our understanding of soil has grown enormously in recent years. The common view of soil was as a source of physical support and chemical substances (natural and artificial) which act as nutrients. Science now understand it to be much more than this - that soil ecology, with soil microorganisms which break down the rocky components of soil, release nutrients in the process, as well as interacting directly with the plant's roots.
Soil structure
Topsoil: This is the top layer of soil that can be seen and that extends to around 15 to 20cm beneath the surface.
Subsoil: This refers to the layers of soil found beneath the 15 to 20cm of topsoil. Depending on the soil type, it is often compacted and less fertile than the topsoil, and less likely to contain organic matter of use to the gardener/food crop grower.
Care of soils
The most valuable resource of a rural person or community is the land, in effect its soils. These may be under mechanical cultivation, untilled permaculture, in pasture or in native forest but if the agriculturist does not properly protect and improve his soils, his intention of forever producing food or other products based on these soils, is a lost battle to start with. Throughout his history, man has destroyed far more soil than remains for his use. This futile act flies in the face of the fact that, it is not all that difficult to defend and improve the soils in use, plus the fact that such improved soils grow crops producing healthier, more nourishing and flavorful foods.
One first produces a healthy soil then you ask of the soil what you want as to planted crops. If you realize that farming or gardening is basically the cultivation of a healthy soil, your chances of success have increased tremendously. The term ‘healthy soil' is literal for the soil is a complex living ecosystem. If the soil is given strong chemical fertilizers, at first crops will grow wonderfully, but then as certain organisms in the soil are discouraged and others are over stimulated, the soil will become completely unbalanced resulting in weakening crops. If even more fertilizer is added in an attempt to remedy this problem, the soil's health will be even further damaged until the soil can become useless.
Soil in construction
Soil is used in natural building (see earthen construction) methods as a building material, as insulation and as thermal mass.
For pages related to soil in construction, see Category:Earthen construction.
See also
- Soil structure
- Soil remineralization
- Healthy soil, healthy plants
- Composting
- Biochar
- Fertilizers
- Manure
- Humanure
- Effective microorganisms
- Growing in permaculture
- Living with the Soil (CTA - GTZ, 28 p.)
- Soil-Friendly Planting
- Soil fertility and management (Peace Corps, 1981, 283 p.)
- Original:Soil Preparation Equipment (GTZ, 1991, 18 p.)
- Soil pH
- History of Soil Science
