Soil Formation 6 E 2 3 Soil is

Soil Formation 6. E. 2. 3 Soil is a mixture of rocks, minerals, decayed material, water, and air. Soil is one of Earth’s most valuable natural resources. Everything that lives on the land, including humans depends on soil.

humus: - Material that forms when plants and animals decay. - dark, organic - makes space for air and water - contains minerals needed by plants - Decomposers help make humus. Earthworms and burrowing animals such as moles mix humus and air into soil. loam: - rich fertile soil made of clay, sand, and silt.

bedrock (parent rock): - solid layer of rock under soil. Wherever bedrock is exposed, soil is always being formed. Why? Soil forms as rock is broken down by weathering. Horizon: - layer of soil that is a different color or texture.

Soil forms in layers called horizons. O horizon: organic layer where plants grow. A horizon: topsoil: humus and tiny rock pieces B horizon: subsoil: middle soil layer, mostly clay C horizon: bedrock (parent rock): partly weathered rocks

fertility: - measure of how well soil supports plant growth - measured from high ------ low - Soil loses its fertility when topsoil is washed away (erosion). - When soil is bare, water and wind carry soil away, plant roots hold soil together and STOP erosion.

Dust Bowl - during 1950’s on Great Plains of U. S. - Farmers in Oklahoma plowed up grass to plant crops. - Dry weather killed the crops which turned the bare soil to dust. - Wind blew the dust creating the Dust Bowl.

Less than ⅛ of Earth’s soil is good for farming. Soil can lose fertility if farmers continuously grow just one kind of plant in the same field year after year. crop rotation- rotating crops to a different field each year to keep soil fertile. contour plowing- plowing in curves on a slope to prevent soil loss. contour plowing

Soil Conservation: - using soil in ways to save it, stop erosion and keep it fertile