3.1 SOIL SOIL FEATURES Soil, which is vital to life on Earth and is the basic factor of every farming activity, develops slowly over time. ONLINE RESOURCES Shale gas Soil composition 1 The basic components of soil are minerals, organic matter, water and air. Typical soil consists of: a solid part: 45% mineral and 5% organic matter; a liquid and a gas part: 20- 30% water and 20-30% air. These percentages are only generalisations because soil is very complex and dynamic. While soil minerals and organic matter hold and nutrients, soil water is what readily provides nutrients for plant Soil air, too, plays an integral role since many of the microorganisms that live in the soil need air to carry out the biological processes that additional nutrients into the soil. As a matter of fact, there is an incredible diversity of organisms that and complete their life cycle below ground level. This community of living micro-organisms and organisms is called the and is made up of one-celled bacteria, algae, fungi, protozoa, nematodes, micro-arthropods, earthworms, insects, small vertebrates, and plants. at best store uptake. release live out soil food web DO Do you think soil composition is basically the same in any location? 1 The role of soils There are five general roles that soils play. Soils: serve as a means for growth of all kinds of plants; modify the atmosphere by emitting and absorbing gases (carbon dioxide, methane, water vapour) and dust; provide habitat for animals that live in the soil (such as and mice) and for organisms such as bacteria and fungi; moles absorb, hold, release and purify most of the water in terrestrial systems; recycled nutrients, including carbon, so that living things can use them over and over again. process Stable, healthy and productive soils are essential for producing most of our food, and for maintaining environmental functions, managing water quality, sustaining our primary industries and supporting rural and urban communities. 1 MORE SDG 15 Life on Land: Protect, restore and promote sustainable use of terrestrial ecosystems, sustainably manage forests, combat desertification, and halt and reverse land degradation and halt biodiversity loss. 1