Soil Taxonomy
This is the highest level of classification in U.S. Soil Taxonomy, dividing soils into twelve groups.
What is the Soil Order.
This concept describes the energy status of water in soil, determining when it moves, when plants can extract it, and why field capacity and the wilting point differ.
What is soil water potential?
Plants take up nitrogen primarily in these two ionic forms.
What are nitrate (NO3−) and ammonium (NH4+)?
The relative percentages of sand, silt, and clay determine this fundamental soil property.
What is soil tecture?
These tiny round worms occupy many trophic levels in soils and can be herbivores, predators, or decomposers. They are extremely numerous and can be a real pest for potato growers.
What are nematodes.
These soils form in very dry climates and commonly contain calcic or gypsic horizons.
What are Aridisols?
The water content at which plants can no longer extract water because soil water potential is approximately −1.5 MPa.
What is the permanent wilting point?
Negative charges on clay and SOM attract and hold positively charged nutrient ions such as Ca2+ and K+.
What is CEC?
This simple ratio of mass of soil solids to the total volume expresses how compacted a soil is.
What is bulk density?
This zone around roots has higher microbial activity because of organic compounds (e.g., sugars) released by the plant. It was one of the hotspots for life in soils.
What is the rhizosphere.
What soil order does the following belong to? Coarse-silty, mixed, superactive, frigid Vitrandic Fragixeralfs
What is an Alfisol?
Water flow in soils driven by gradients in total soil-water potential follows this law.
What is Darcy's Law?
A biochemical process in which microbial decomposition makes nutrients available for root uptake.
What is mineralization?
Clay soils resist shear because the particles are attracted by electrostatic forces. This attraction between charged surfaces is called what?
What is cohesion?
These fungi colonize roots and improve uptake of phosphorus and micronutrients.
What are mycorrhizal fungi?
This diagnostic surface horizon is very dark, ≥25 cm thick, with high organic carbon, high base saturation, and granular structure.
What is a mollic epipedon?
The ease with which water moves through soil depends on this property, which decreases dramatically as soil dries due to loss of water-filled pathways.
What is hydraulic conductivity?
This soil condition occurs when salts accumulate in the root zone, reducing plant water uptake and causing nutrient imbalances.
What is salinity?
Dry sands rely mostly on this force between particles to resist sliding. When it is lost, the soil collapses or flows.
Most carbon and energy entering soil food webs originate from this source tied to photosynthesis.
What are primary producers?
Soil Taxonomy recognizes that pedons of the same order can look very different. This framework, abbreviated CLORPT, explains those differences by attributing soil characteristics to five key formation factors: climate, organisms, relief, parent material, and this final factor.
What is time?
This curve explains why soils with a finer pore-size distribution retain more water but transmit it less effectively than coarse soils.
What is the water-retention characteristic?
This process occurs when one ion replaces another of similar size in a clay mineral structure, creating permanent negative charge that increases a soil’s ability to hold nutrient cations.
What is isomorphic substitution?
This gas produced during root and microbial respiration must move out of the soil, or roots can "suffocate."
What is CO2?
Healthy soils contain a wide variety of organisms at many trophic levels. This measure refers to the number of different species present.
What is biodiversity?