Soil, the living skin of the land

When you come in from playing outside, there may be soil on your hands and shoes. Soil is all around us, and it is very important. Soil holds water and air for plant roots, gives plants nutrients and keeps them standing upright. Almost all the food we eat depends on soil, either directly, like wheat and tomatoes, or because the animals we eat feed on plants that grew in soil. Soil is also a home to many living things, such as worms, insects, fungi and bacteria. Soils are not all the same. Some are pale and gritty, some are dark and crumbly and some are sticky when wet. In the Nile valley the soil is dark and fertile, which is why farms have grown there for thousands of years. If a soil slowly turned into a very different kind, the plants and animals that depend on it might not survive.