Ultimate soils study guide - SC

2025-2026 Envirothon

soil

A mixture of minerals, organic matter, air, and water that forms the top layer of the Earth’s surface and supports plant and animal life.

importance

Supports plant growth, provides habitats, filters water, carbon cycle, and  climate change mitigation

properties

 texture, structure, porosity, color, organic matter content, chemistry, pH, and nutrient availability 

diagnostic significance of color

Drainage class

diagnostic significance of color

How much organic matter is present

diagnostic significance of color

Where the soil came from

diagnostic significance of color

Provides clues about soil fertility, drainage, and mineral composition

mussel soil color chart

how soil color is measured

hue

specific color

value

lightness

chroma

color intensity

weathering

The breakdown of parent material impacts soil color

yellow, orange

Granitic parent materials lead to ____ or ______ hues

volcanic rocks

_______ can result in pink, orange, white, or green soils

redox

Iron can create red or yellow oxides when it oxidize

red

_____ color indicates well-drained soils (iron is easily oxidized)

yellow brown

____ color indicates poor drainage

anaerobic

In ______ conditions, iron is reduced to a gray color

manganese

____ can also form oxides in poorly drained soils

dark

• Decomposing organic matter (plants and animals) adds a ____ colored humus, which makes your soil appear dark brown or black 

leaching

Downward movement of water can leach out iron and manganese oxides, especially in soils with high precipitation, leading to lighter, bleached colors

lighter

more leaching means ____ colors

12

number of soil orders

entisols

soil order

inceptisols

soil order

andisols

soil order

mollisols

soil order

alfisols

soil order

spodosols

soil order

ultisols

soil order

oxisols

soil order

gelisols

soil order

histosols

soil order

aridisols

soil order

vertisols

soil order

parent material

The original rock from which soil forms determines the initial size distribution of particles, which influences textures 

climate

Temperature and precipitation rates affect the rate of weathering and chemical reactions, influencing texture and structure 

topography

Slope and elevation affect erosion and deposition, influencing soil development and structure

organisms

Plants, animals, and microorganisms contribute to soil aggregation and organic matter content, impacting the structure

time

The length of time soil has been developing impacts its maturity and the extent of changes in texture and structure 

tillage

can damage aggregates and reduce soil structure 

compaction

 Heavy machinery and livestock traffic can compact soil, reducing the porosity and altering the structure 

vegetation removal

Loss of vegetation reduces organic matter and the ability of roots to bind soil particles, which impacts structure 

soil erosion

Removal of topsoil can alter the texture and structure 

smaller

Soils with _____ particles (silt and clay) have a larger surface area and can hold more water

CEC

the soil’s ability to hold positively charged nutrients like nitrogen, phosphorus, and potassium

CEC

Clay-rich soils have a higher:

CEC

cation exchange capacity

erode

Different soils ____ at different rates based on how they are made up and their structure

texture, structure

Soil ____ and ____ affect the rate at which water infiltrates into the soil from the surface

Infiltration

______ contributes to groundwater recharge, which is a key part of the hydrologic cycle 

plant nutrients

Soil pH, texture, and organic matter content influence the availability of essential:

microorganisms

______ in the soil play a crucial role in decomposing organic matter, releasing nutrients, and transforming them into forms available to plants 

parent material, climate, topography, organisms, time

five factors of soil formation

parent materials

soil ____ originate from various sources, primarily rocks and minerals that are weathered and transported through different processes

sand

the largest particles (0.05 to 2.00)

sand

contribute to good drainage and aeration

sand

low water holding capacity

silt

intermediate in size (0.002 to 0.05 mm)

silt

provides a balance between drainage and water retention

silt

 is fertile

clay

 the smallest particles (less than 0.002 mm)

clay

• , hold water and nutrients well, but can lead to poor drainage if present in high proportions 

organic matter

contributes to soil’s fertility and aeration, enhances water retention, nutrient availability, and biological activity

organic matter

Improves soil structure by binding particles together 

MLRA

major land resource areas

MRLAs

differ in their topography, soils, and vegetation, leading to distinct land management and resource utilization practices 

blue ridge

2% of the state

blue ridge

metaphoric rocks (granite, gneiss, schist)

blue ridge

soils: loamy - Edneyville, Saluda

blue ridge

westernmost part of the state

blue ridge

features rugged terrain and is home to a variety of ecosystems, like forests and streams

piedmont

a region of rolling hills that is known for its diverse range of soils

piedmont

major agricultural area in the state

piedmont

32% of the state

piedmont

igneous and metamorphic rocks (granite, gneiss, diabase)

piedmont

sedimentary rocks (siltstone)

piedmont

Soils: deep, red, clayey, Cecil, Appling, high shrink-swell, Iredell, Brewback 

sand hills

A distinctive area characterized by sandy soils and pine forests 

sand hills

The transitional zone between the piedmont and the coastal plain 

sand hills

15% of the state 

sand hills

Eolian sands, ancient river deposits, and weathered clays 

sand hills

Sandy to fine-loamy soils - alpin, alley 

coastal plain

A variety of marine sediments are all oriented more or less parallel to the coastline

coastal plain

The inner coastal plains consist of rolling hills 

coastal plain

Outer coastal plains consist of flat terraces 

coastal plain

Vegetation consists of pine-dominated forests with agricultural land interspersed on better-drained sites, hardwood forests along low-gradient streams, and pine forests on less well-drained terraces 

coastal plain

50% of the state 

coastal plain

Marine deposits and river deposits 

coastal plain

Soils are sandy to clayey, well drained to very poorly drained, dothan (well drained), rains (poorly drained) 

healthy soil benefit

supports plant growth

healthy soil benefit

Improved water infiltration and retention 

healthy soil benefit

holds more water by binding it to organic matter

healthy soil benefit

Reduced erosion 

healthy soil benefit

Carbon sequestration 

healthy soil benefit

Enhances biodiversity 

healthy soil benefit

Improves air and water quality 

healthy soil benefit

Reduced reliance on synthetic fertilizers and irrigation 

improve soil health

Maximizing soil cover helps to:

improve soil health

Minimizing soil disturbance helps to: