- A horizon
- consists of a mixture of organic material with inorganic products of weathering
- B horizon
- soil layer that is an accumulation of mostly fine material that has moved downward
- bedrock
- solid rock that lies beneath the soil
- C horizon
- layer of soil that contains the parent material, and the organic and inorganic material that is broken down to form soil; also known as the soil base
- clay
- soil particles that are less than 0.002 mm in diameter
- epiphyte
- plant that grows on other plants but is not dependent upon other plants for nutrition
- horizon
- soil layer with distinct physical and chemical properties, which differs from other layers depending on how and when it was formed
- humus
- organic material of soil; made up of microorganisms, dead animals, and plants in varying stages of decay
- inorganic compound
- chemical compound that does not contain carbon; it is not part of or produced by a living organism
- insectivorous plant
- plant that has specialized leaves to attract and digest insects
- loam
- soil that has no dominant particle size
- macronutrient
- nutrient that is required in large amounts for plant growth; carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur
- micronutrient
- nutrient required in small amounts; also called trace element
- mineral soil
- type of soil that is formed from the weathering of rocks and inorganic material; composed primarily of sand, silt, and clay
- nitrogenase
- enzyme that is responsible for the reduction of atmospheric nitrogen to ammonia
- nodules
- specialized structures that contain Rhizobia bacteria where nitrogen fixation takes place
- O horizon
- layer of soil with humus at the surface and decomposed vegetation at the base
- organic compound
- chemical compound that contains carbon
- organic soil
- type of soil that is formed from sedimentation; composed primarily of organic material
- parasitic plant
- plant that is dependent on its host for survival
- parent material
- organic and inorganic material in which soils form
- rhizobia
- soil bacteria that symbiotically interact with legume roots to form nodules and fix nitrogen
- rhizosphere
- area of soil affected by root secretions and microorganisms
- sand
- soil particles between 0.1–2 mm in diameter
- saprophyte
- plant that does not have chlorophyll and gets its food from dead matter
- silt
- soil particles between 0.002 and 0.1 mm in diameter
- soil
- outer loose layer that covers the surface of Earth
- soil profile
- vertical section of a soil
- symbiont
- plant in a symbiotic relationship with bacteria or fungi