Soil Science Vocabulary

Flashcards covering vocabulary terms for soil fertility.

Soil

Weathered upper surface of the Earth's crust that supports plant growth

Soil Forming Factors

Parent Material, Climate, Topography, Organisms, Time, Humans

Aeolian

Wind blown sediment

Soil Forming Processes

Additions, Losses, Translocations (up and down), Transformations (chemical change)

Soil Physical Processes

Color, Texture, Structure, Profile, Density, Pore Space, Aggregation, Water-Holding Capacity

Sand

Gritty

Silt

Smooth

Clay

Sticky

Soil Textural Classes

Sand - 50%, Silt - 15%, Clay - 35%

Soil Structure

Granular < 0.5 cm, Platy, Blocky 1.5-5cm, Columnar, Single-grained

Particle Density

mp/vp

Bulk Density

mp/vb

Low pore space

High Db implies…

Water Potentials

Force that causes water to move or not

Gravitational Water Potential

Acceleration due to gravity x soil height

Matric Water Potential

Adhesion and Capillarity

Osmotic Water Potential

Water movement across a semipermeable membrane to equalize concentration of solutes

Plant Water Use

Evapotranspiration

Types of Water Movement in Soil

Saturated Flow, Unsaturated Flow, Vapor Movement

Types of Irrigation

Surface (Flood), Sprinkler, Drip

What is pH?

Concentration of H+ ions in a solution

5 Sources of H+

Carbonic Acid, SOM, Fertilizers, Cation Uptake, Precipitation

Liming Materials

CaCO3 - Calcium Carbonate (Limestone), CaO - Calcium Oxide (Quick Lime), Ca(OH)2 - Calcium Hydroxide, CaMg(CO3)2 - Dolomite, CaSO4 - Gypsum

Liming Methods

Slow Reaction, Few weeks: Quick Lime and Slaked Lime, Year: Finely ground limestone

Salinity

Recharge - where H2O comes from, Discharge - where H2O evaporates, Seep - whole network of recharge-discharge

What Causes Saline Seepage?

Contact/Slope, Depression Bottom, Slough Ring, Hydraulic Discharge, Outcrop Mechanism, Canal Seepage

Crops for Discharge Area

Salt-tolerant species, Wheatgrasses, wild rye, sweet clover, alfalfa, bromegrass, Sugar beets, barley, safflower, sunflower, wheat

Types of Erosion

Splash Erosion, Sheet Erosion, Rill Erosion, Gully Erosion

Solutions for Water Erosion

No till and plant different, Grass waterway, Contour cropping, Strip cropping, Terraces

Solutions for Wind Erosion

Stabilize soil aggregates, Cover crops, No till, Rotate entrance, Manure, Reduce wind velocity at soil surface, Shelterbelt

WIND EROSION EQUATION

E = ICKLV

Management for Sodic Soil

Good drainage, Fertilizer, Irrigation, SOM, Deep-tillage

SOM and Soil Organisms

Raw residues and microorganisms- 1-10% of soil composition, usually vegetation

Active fraction

10-40% of soil composition

Stable fraction

40-60% of soil composition

Decomposition rates of organic compounds

Sugars, starches, simple proteins decompose fastest, while lignins and phenolics decompose slowest

Cellulose

A polymer consisting of 7000-15000 sugar units

Lipids

Hydrophobic compounds found in soil

C-C bonds

The main energy source for microorganisms in soil

Mineralization

The process by which soil organic matter decomposes and releases inorganic nutrient forms

Immobilization

Microbial uptake of mineral nutrients, making them temporarily unavailable

Leaching

The influence of soil organic matter chelates and micronutrient cations

Nutrient capture by plants

The process by which plants access nutrients from the soil

Carbon:nutrient ratio

A metric that powers microbial growth and reproduction, with C:N ratios of 25:1, 20:1 favoring plants, and 30:1 favoring microbes

Soil Organism Roles

Includes plants, shredders, decomposers, and nutrient transformers

Earthworms

Soil organisms that stimulate microbial activity, mix and aggregate soil, and improve water -holding capacity

Factors promoting earthworms

Presence of fresh undecomposed organic matter, pH > 5.8, moisture, and temperature of 50°F

Factors depressing earthworm populations

Droughty soils, anhydrous ammonia, and tillage

Dung Beetles

Insects that feed on animal waste, which serves as a nutrient source

Soil Health

The ability of soil to carry out essential functions such as water regulation and nutrient cycling

Soil health indicators

Metrics that include infiltration rate, soil respiration, earthworm counts, and plant diversity

Functional Diversity

The ability of soil organisms to utilize a wide range of substrates and carry out many processes

Functional Redundancy

The overlap of different species roles, leading to stability and resilience in ecosystems

Keystone species

Species whose presence contributes to the diversity of life, and whose extinction would ruin the ecosystem

Mycorrhizal fungi

Fungi that help roots grow to nutrients and water

Mass Flow

The movement of nutrients through soil due to concentration gradients

Leaching

Influence of SOM chelates and micronutrient cations

What is Functional Diversity?

Ability of soil organisms to utilize a wide range of substrates and carry out many processes

Functional Redundancy

Different species roles overlap, leading to stability and resilience

What is a keystone species?

Species presence contributes to diversity of life; extinction would ruin the ecosystem

What do earthworms do?

Stimulate microbial activity, mix and aggregate soil, increase nutrient availability

Dung Beetles

Animal waste that serves as a nutrient source and decomposer food source

Soil health

Ability to carry out essential functions like water regulation and nutrient cycling

Soil health indicators

Include infiltration rate, soil respiration, earthworm counts, and plant diversity

Water regulation

Measured by infiltration rate, surface crusting, and water-holding capacity

Sustaining plant and animal life

Indicators include soil cover, earthworm counts, and plant diversity

Filtering and buffering

Measured by pH, buffer pH, and groundwater quality

Physical stability and support

Indicators include soil aggregates, soil density, and evidence of erosion

Saline soils

Soils that require leaching to remove excess salt

Subsurface drainage water quality concerns

Loss of Nitrogen and other nutrients, pesticide/herbicide contamination, canal seepage

Saturated Buffer

Diverts a portion of drain tile water into a vegetated buffer strip where plants remove nitrogen

Bioreactor

An underground trench filled with wood chips where microbial activity breaks down nitrogen in water

Constructed Wetlands

Water is diverted through a wetland with microbes and vegetation that slows water movement and causes denitrification

Components of Soil Organic Matter (SOM)

Raw residues and microorganisms (1-10%), Active Fraction (10-40%), Stable Fraction (40- 60%)

SOM as a revolving bank account

You get out what you put in; deposit organic materials to maintain a healthy SOM balance

Required SOM for suitable soil physical properties

3-5% SOM is necessary for optimal soil structure and stability

Purpose of maintaining SOM above 3-5%

Improves soil structure, stability, water-holding capacity, nutrient supply, and biodiversity

Impacts of tillage on soil physical properties

Degrades soil structure, compacts soil, and increases risk for wind and water erosion

Tillage effects on SOM cycles

Accelerates decomposition of SOM and disrupts soil microbial communities, altering nutrient cycling

Soil erosion

The process by which soil is removed from the land surface, often exacerbated by poor management practices

Nutrient cycling

The process of nutrients being reused and recycled in the ecosystem

Soil Aggregation

The clustering of soil particles into aggregates, improving soil structure and function

Decomposition

The breakdown of organic matter by microorganisms, releasing nutrients back into the soil

Biodiversity in soil

The variety of life forms in the soil, contributing to ecosystem resilience and function

Water-holding capacity

The ability of soil to retain water for use by plants

Buffering pH

The ability of soil to resist changes in pH, maintaining a stable environment for organisms

Soil structure

The arrangement of soil particles and the pore spaces between them, affecting water movement and root growth

Microbial activity in soil

The actions of microorganisms that contribute to nutrient cycling and organic matter decomposition