soil

What is Florida's official state soil, designated in 1989?

Myakka fine sand.

How many acres of Myakka fine sand exist in Florida, and is it found anywhere else in the U.S.?

More than 1.5 million acres; it does not occur anywhere else in the United States.

What is soil, broadly defined?

A complex, self-renewing, living system composed of inorganic minerals, organic humus, living organisms, moisture, and air.

What is the study of soils called?

Pedology (from Greek pedon = soil, logos = reason); often called "soil science" in the U.S.

Who introduced the idea that climate plays a major role in soil formation (in the U.S., in 1920)?

C.F. Marbut, chief of the U.S. Soil Survey.

Name the five soil-forming factors.

Parent material, climate, plant and animal life (organisms), relief (topography), and time.

What is "parent material"?

The unconsolidated, chemically weathered mineral, rock, or organic matter from which soil forms.

What is a soil profile, and what are the layers within it called?

A vertical column of soil (e.g., visible in a road cut); the layers are called horizons.

Describe the O horizon.

Dominated by organic material — fresh and decaying plant matter (leaves, needles, twigs, moss).

Describe the A horizon.

Formed at/near the surface; an accumulation of organic matter and minerals, generally darker, where most root activity occurs (often called the "surface layer").

What happens in the E horizon?

Loss (eluviation) of silicate clay, iron, and/or aluminum, leaving a concentration of sand/silt particles.

What is the B horizon often called, and why?

The "zone of accumulation" — it receives leached materials washed down from upper horizons (subsoil).

What is leaching?

The process by which water washes/moves soil components downward from the A horizon into the B horizon.

What is the C horizon?

The substratum — partially disintegrated parent material, less affected by soil-forming processes.

What is the R horizon?

Bedrock — the very lowest horizon.

What is fragipan? What is claypan? What is hardpan (Florida term)?

Fragipan: a dense, nearly impermeable subsurface layer. Claypan: fragipan from extreme compaction. Hardpan: Florida's term for a layer cemented by soil particle cementation.

What is a "mature" soil vs. an "immature" soil?

Mature soil has clearly defined horizon layers; immature soil lacks well-developed layers.

What does the suffix "t" mean when added to a horizon letter (e.g., Bt)?

Accumulation of alluvial clay.

What does the suffix "g" indicate in a horizon designation?

Strong gleying — soil formed under poor drainage, showing gray colors/mottles from reduced iron.

What does "soil texture" refer to?

The percentages of sand, silt, and clay in a soil sample (mineral particles smaller than 2mm).

List the three basic soil separates from largest to smallest particle size.

Sand, silt, clay.

How many major USDA textural classes are there?

12 (sand, loamy sand, sandy loam, sandy clay loam, sandy clay, clay, clay loam, loam, silt loam, silty clay loam, silty clay, silt).

What field test distinguishes sand, silt, and clay by feel?

Squeeze moist soil in your hand: sand won't hold shape; silt clumps together; clay can be spread into ribbons and holds its shape.

What is "mechanical analysis"?

The laboratory procedure by which the percentages of soil separates (sand/silt/clay) are determined.

Using the USDA textural triangle, a soil sample analyzed as 20% sand, 40% silt, and 40% clay would fall into which general textural family? (Hint: high clay + roughly balanced silt)

Clay loam (specifically consult the triangle, but the combination of moderate-high clay with balanced silt places it in the clay loam region).

What tool is used to measure/standardize soil color descriptions?

The Munsell Soil Color chart.

What are the three characteristics used to describe Munsell soil color chips?

Hue, value, and chroma.

What does "hue" indicate on the Munsell chart?

The color's relation to spectral colors (red, yellow, green, etc.) — e.g., "YR" = yellow-red.

What does "value" indicate?

The relative lightness or darkness (0 = absolute black, 10 = absolute white).

What does "chroma" indicate?

The color's purity/vividness vs. grayness (0 = neutral gray, increasing to ~20).

Write the order of a Munsell notation.

Hue, value, chroma (e.g., 5YR 5/6 = yellowish-red).

What is the general rule of thumb linking soil color to fertility?

Darker soils tend to be more fertile.

What is soil porosity?

The amount and size of spaces (pores) between soil or rock particles.

What is soil permeability?

The rate at which water and air move downward through saturated soil (internal drainage).

About what percentage pore space does a healthy topsoil have?

About 50%.

What is soil compaction, and which soil pores are most vulnerable to it?

The destruction of soil pores from tillage, traffic, or heavy equipment; macropores (largest pores) are most vulnerable.

Why does loss of macropores matter for plant/microbial life?

It restricts oxygen and gas movement into/out of the soil, which plant roots and many microorganisms need.

What do micropores primarily do?

Hold and retain water in the soil; their loss lowers permeability and increases runoff, erosion, and flooding.

If a soil has a measured permeability rate of 0.5 in/hr, which permeability class does it fall into? (Classes: very slow

Moderately slow (0.2–0.6 in/hr range).

Name the seven natural soil drainage classes, from best-drained to worst-drained.

Excessively drained, somewhat excessively drained, well drained, moderately well drained, somewhat poorly drained, poorly drained, very poorly drained.

What visual soil feature is generally ABSENT in excessively and somewhat excessively drained soils, but present in wetter classes?

Mottling (related to wetness/poor drainage).

How is a "wetland" generally defined in terms of saturation duration?

An area where soil is covered/saturated with fresh or salty water for at least one month per year, supporting specially adapted vegetation.

What percentage of federally listed endangered plants and what percentage of listed birds depend on wetlands (per the guide)?

90% of listed plants; 30% of listed birds (also 15% of mammals and 50% of fish on the endangered list).

About what percentage of Florida's original 20 million wetland acres has been lost, and what share of the nation's remaining wetlands does Florida still hold?

About 60% lost; Florida still contains more than 20% of the remaining wetlands in the U.S.

In what year was the Soil Taxonomy classification system developed?

1951.

Name the six taxonomic categories in Soil Taxonomy, from broadest to most specific.

Order, suborder, great group, subgroup, family, series.

How many soil orders exist total, and how many are found in Florida?

12 total soil orders; 7 are found in Florida.

Which soil order is composed of thick (16+ inch) organic material like muck and peat?

Histosols.

Which soil order has little to no horizon development?

Entisols.

Which soil order has a spodic horizon (dark subhorizon of organic matter + aluminum, with or without iron) and is common in Florida's sandy, acid, often poorly drained soils?

Spodosols.

What distinguishes Ultisols from Alfisols?

Both have an argillic (clay-accumulation) horizon, but Ultisols are more developed/leached with less than 35% base saturation, while Alfisols have 35%+ base saturation.

Which soil order has a thick, dark, base-rich surface horizon (mollic epipedon)?

Mollisols.

Name at least four land uses that depend on soil knowledge, per the guide.

Farming, ranching, forestry, recreation, wildlife habitat, and engineering uses (building sites, roads, sanitary facilities).

What soil qualities matter most for recreational uses like camping and playgrounds?

Mild slopes, few/no stones, good rainfall absorption while remaining firm, not dusty when dry, not subject to flooding.

What is a primary factor in evaluating wildlife habitat quality related to soils?

Plant diversity in the area — soils affect what vegetation is available as food/cover.

What is the difference between geologic (natural) erosion and accelerated erosion?

Geologic erosion occurs slowly over long geologic time periods; accelerated erosion is much faster, mainly from human/animal activity or catastrophes (hurricanes, wildfires).

What is the first principle of wind erosion control?

Cover the soil (vegetative cover slows wind, protects particles, traps blowing soil).

Name several agricultural conservation practices that reduce erosion.

Crop residue management, crop rotation, cover crops, strip cropping, buffer strips.

How does soil erosion contribute to nonpoint source pollution beyond just losing soil?

Sediment clogs waterways, reduces aquatic habitat/spawning areas, and reduces water clarity, inhibiting aquatic plant growth.

What do nitrogen-fixing bacteria do, and what plants commonly host them?

They convert atmospheric nitrogen (N2) into a plant-usable form; commonly form symbiotic nodules with legumes (clover, lupine) and trees like alder.

What is the difference between nitrifying and denitrifying bacteria?

Nitrifying bacteria convert ammonium to nitrite then nitrate (aerobic); denitrifying bacteria convert nitrate back to nitrogen gas (anaerobic).

What soil organisms are responsible for the "earthy" smell of freshly turned healthy soil?

Actinomycetes.

What are mycorrhizal fungi, and what do they exchange with plants?

Mutualist fungi that colonize plant roots; in exchange for plant carbon, they help solubilize and deliver phosphorus and other nutrients to the plant.

What is the difference between ectomycorrhizae and endomycorrhizae?

Ectomycorrhizae grow on the surface of roots (common with trees); endomycorrhizae grow within root cells (common with grasses, row crops, shrubs).

What do protozoa mainly feed on, and what beneficial byproduct do they release for plants?

They feed primarily on bacteria; they release excess nitrogen as ammonium, which becomes available to plants.

What are the four broad dietary groups of free-living nematodes?

Bacterial-feeders, fungal-feeders, predatory nematodes, and omnivores (root-feeders are plant parasites, not free-living).

What soil-dwelling group gets its name from jointed legs and includes springtails, mites, and millipedes?

Arthropods.

What is the ecological role of "shredder" arthropods like millipedes and sowbugs?

They chew up dead plant matter, increasing surface area for microbial decomposition (like a "can-opener" for bacteria).

What three major ecological groups do earthworms fall into based on feeding/burrowing habits?

Epigeic (surface/litter dwellers), endogeic (upper soil dwellers, feed on soil/organic matter), and anecic (deep-burrowing, e.g., night crawlers).

How do earthworms improve soil structure and water infiltration?

By fragmenting organic matter, mixing/aggregating soil into casts, and creating burrows that increase porosity and drainage.

A farmer switches from conventional tillage to no-till farming. What happens to earthworm populations, and why?

Earthworm populations (especially night crawlers) tend to increase, because surface crop residue builds up, providing more food and habitat that earthworms rely on.