6th Grade - Soil

Permeable

Characteristic of a material that is full of tiny, connected air spaces that water can seep through. Sandy top soil is permeable because water drains quickly through the spaces between the sand particles.

Soil

The loose, weathered material on Earth's surface in which plants can grow.

Bedrock

The solid layer of rock beneath the soil. Soil formation begins with the weathering of bedrock.

Humus

Dark-colored organic material in soil formed as plants and animals decay (break down). When earthworms add their wastes to the soil, then die and decay in the soil, they are contributing to the formation of humus.

Fertility

A measure of how well soil supports plant growth. Soil that is rich in humus has high fertility.

Loam

Rich, fertile soil that is made up of about equal parts clay, sand, and silt. The best type of soil in which to grow plants.

Soil horizon

The layer of soil that differs in color and texture from the layers above or below it. There are three soil horizons A, B, and C.

Topsoil

Mixture of humus, clay, and other minerals that forms the crumbly, topmost layer of soil. The A soil horizon is made of topsoil.

Subsoil

The layer of soil beneath the topsoil that contains mostly clay and other materials, but little organic matter. The B soil horizon is made of subsoil.

Litter

The loose layer of dead plant leaves and stems on the surface of the soil.

Decomposers

Soil organisms that break down the remains of organisms and digests them. Crucial (very important) to soil formation. What bacteria and fungi in soil are called.

A horizon

the layer where you find the most decomposers

C horizon

where you find partly weathered rock

Living organisms

These mix the soil and make humus.

B horizon

The B horizon is also called subsoil. A soil horizon composed primarily of mineral material with very little organic matter

Porous

Full of tiny holes, that aren't necessarily connected.

Weathering

The breaking down of rocks and other materials on the Earth's surface.