Soil Mixture of organic matter and broken down rocks. Often containing sand, clay, and water. Acts as an ecosystem for thousands of organisms.

SOIL: Horizons Figure 3-23 2

Soil has different layers called “Horizons” • A horizon: Also known as top soil. → Decomposed organic matter. → Highest level of nutrients. → Thousands of bacteria live here. → Shallow plant roots and fungi. B horizon: aka…subsoil. → mix of organic matter+eroded rocks. Less nutrients / life compared to the top soil.

Soil has different layers called “Horizons” • C horizon: a.k.a parent material. → High amount of rocks + minerals. Not that much organic matter. Bedrock → Large Rock slabs that haven't eroded yet. The bottom origin of the soil. Tree roots usually stop above this point.

Formation of Soil 1: Weathering/erosion break up rock -released nutrients that algea, lichen, and bryophytes such as moss need to grow. WEATHERING / EROSION Break down Move

Formation of Soil 2: Decomposers create a layer of top soil (horizon A) → Organic matter from the top mixes with parent material from the bottom. → B horizon grows over time.

Nutrient-rich Top Soil The layer of decomposing organic matter in the top soil is called “Humus.” More humus = more nutrients.

Soil Separates Most soils have a combination of soil particles sizes Sand Silt Clay

12-14 Nutrients plants need to survive Primary Nutrients 12-14 Nutrients plants need to survive Plants need certain nutrients in very large quantities in order to grow + reproduce. The primary nutrients are NITROGEN (N), PHOSPHORUS (P), and POTASSIUM (K).

Primary Nutrients Nitrogen -Rapid growth -Increased seed & fruit production   Phosphorus -Encourages blooming & root growth Potassium -Fruit quality -Reduction of diseases.

Soil pH is a factor Soil pH is one of the most important soil properties that affects the availability of nutrients.  Nutrients tend to be less available in soils with very low or very high pH.

Depleting Soil Nutrients Agriculture (uses up nutrients) Removing Trees (Increases Erosion) Pollution (Human activity / waste adds toxic chemicals to soil)