What are we going to learn…  Soil-Why is it important? Why is it important?  What is soil?  Sand, Silt and Clay  What’s a soil profile?  Horizons?  Not all soil is brown  Running out of dirt!

So what is Soil? Soil is a mixture of rock and mineral particles and organic matter. Soil covers the earth in a thin layer and it is very important in plant growth. Watch the video from my blog after this slide

Why should I care about soil? Soil is the #1 support for plants Soil anchors the plants roots so that they don’t fall over Soil is a superstore of nutrients For a plant to grow it needs 16 elements! (13 come from the soil!) Moisture for the plants is stored in the soil Animals depend indirectly on soil since they eat plants and other animals that eat plants.

Soil Formation The weathering of rocks on the Earth’s surface results in the formation of soil. Soil is formed when rocks are continuously broken down by weathering. As rocks weather, they break into smaller pieces. These pieces are broken down into even smaller pieces to form soil.

4 Basic Processes in the Formation of Soil ADDITIONS LOSSES TRANSLOCATIONS TRANSFORMATIONS (MOVEMENT WITHIN THE SOIL) (ONE COMPONENT CHANGES TO ANOTHER)

ADDITIONS Rain adds WATER. Dust adds MINERALS. Animal waste add ORGANIC MATTER and NUTRIENTS. Humans add FERTILIZER.

LOSSES WATER evaporates into the air. Soil particles WASH AWAY in storms. ORGANIC MATTER may compose into carbon dioxide. NUTRIENTS and MINERALS leach into groundwater or are taken up by plants.

TRANSLOCATIONS MOVEMENT WITHIN THE SOIL GRAVITY pull WATER down from top to bottom. EVAPORATING WATER draws minerals up from bottom to top ORGANISMS carry materials in every direction.

TRANSFORMATIONS Dead leaves decompose into HUMUS. Hard rock WEATHERS into soft clay Oxygen REACTS with iron, “oxidizing” the soil into a reddish color. (ONE COMPONENT CHANGES TO ANOTHER)

The older a soil gets, the more different it looks from its parent material. Soil is always changing – minerals, water, air, organic matter and organisms – always change. Looks Change With Age

There are five components of soil: 1. Rock 2. Sand 3. Silt 4. Clay 5. Humus

Rock Rock is solid and made of minerals

Sand Sand is tiny grains of worn down rock. It doesn’t hold water or have many nutrients.

Silt Silt is very small, broken pieces of rock. It is larger than clay, but smaller than sand. It is powdery when dry. Sand Silt Clay (smaller particles)(larger particles)

CLAY Clay holds water well. It is sticky and can be shaped when it is wet. But, it is very hard when dry. Clay has many nutrients. Clay is used for adobe or brick houses.

Humus Humus is made of leaves, twigs, small animals, or other decayed substances. Humus adds many nutrients to the soil. Humus is in the topsoil.

United States Department of Agriculture Soils are very different, depending on how they form

Different Compositions of Soil The composition of soil varies from place to place. The type of rock broken down by weathering determines the kinds of minerals in the soil. The type of weathering also affects the composition of soil. Mechanical weathering produces soil with a composition similar to the rock being weathered. Chemical weathering produces soil with a different composition.

Pore Spaces Air and water fill the spaces between soil particles. These are called pore spaces. Plants and animals use the water and air in these spaces, as well as the minerals dissolved in water. Pore spaces provide needed oxygen for healthy plant root growth.

Soil Texture The type of weathering also affects soil texture. Texture refers to the size of the individual soil particles. Soil particles vary from very small to large. Both mechanical and chemical weathering first breaks rocks into gravel (2-64mm) and then in sand (less than 2mm) and finally into silt.

Soil Horizons As soil forms, it develops separate soil layers called horizons. Each soil horizon is different. A cross section of the soil horizons is called soil profile. A soil profile shows the different layers of soil. Soil that has developed three layers is called mature soil. It takes thousands of years and the proper conditions for soil to develop three layers.

What is a Soil Profile? A Soil Profile is a vertical cross-section of layers of soil found in a given area. Below are two examples of soil profiles.

What is a Soil Horizon? Soil horizons are the layers in a soil profile used to classify soil types. Horizons based on color, texture, roots, structure, rock fragments, and any unique characteristic worth noting. Master Soil Horizons are depicted by a capital letter in the order (from top down): O, A, E, B, C, and R