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What Is Soil?

Soil is the loose top layer of Earth's surface. Plants depend on soil. It holds them up. It provides them with food and water.

Soil is made of . These very small pieces mostly come from rocks broken down by weathering. Other soil particles come from rotting remains of plants and animals. The part of soil that comes from living things is called .

Soil Life

Many small organisms live in soil. They include worms, bacteria, and fungi. are like plants, but they aren't green. And they have no leaves, flowers, or roots. The organisms feed on dead plants and animals. They cause them to , or break down. The decayed plant and animal matter is called . Humus makes the soil dark. It provides nutrients plants need to grow.

Soil Layers

Soil develops in layers. The top layer consists mostly of humus. It is called .

The next layer down is called . Subsoil contains more rock particles than topsoil and less humus. It is not as good for growing plants.

The layer below the subsoil has many pieces of rocks. The pieces get bigger when they are deeper in the ground. Most plants cannot grow in this rocky layer.

The soil layers all rest on solid rock. It is called . The pieces of rock in soil come from bedrock.

Types of Soil

There are many types of soil. Soils can be many colors. They can also have different textures. is the is the size of the particles that make up soil.

Clay is a type of soil with very small particles. The particles are packed together tightly. Clay can hold a lot of water, which makes it heavy and sticky.

Sand has much larger particles than clay. It feels rough. There's a lot of air space between the particles, so water drains through this soil easily.

contains a mix of sand and clay. Loam is the best soil for growing plants. It lets just the right amount of water pass through for plant roots to take in.

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