Soil Science Vocabulary – Fertilizers, Erosion, Conservation, Survey & Classification

115 vocabulary flashcards summarizing fertilizer application methods, soil-erosion concepts, conservation practices, soil survey procedures, and the USDA soil classification system.

In-the-row application

Fertilizer placed along the bottom of a furrow where the crop row will be established.

Ring application

Fertilizer distributed in a circular band around the base of a plant or tree.

Hole application

Fertilizer dropped into several holes spaced around a tree.

Spot application

Small amounts of fertilizer placed beside each hill or individual plant.

Basal application

The first dose of fertilizer given at planting time.

Topdressing

Fertilizer applied sometime after crop emergence.

Fertigation

Applying dissolved fertilizer through irrigation water.

Soil erosion

Detachment and transport of soil by water, wind, or gravity to a new location.

Detachment (erosion)

Raindrop splash or other forces that loosen soil particles from the surface.

Entrainment

Transport of detached soil particles downslope in runoff or wind.

Deposition

Settling of eroded sediments under gravity; rapid for sand, slow for clay.

Raindrop erosion

Soil particle splash caused directly by the impact of falling raindrops.

Sheet erosion

Uniform removal of a thin soil layer by runoff; often unnoticeable until subsoil appears.

Rill erosion

Numerous shallow channels a few centimetres deep formed by running water between crop rows.

Gully erosion

Enlarged rills forming channels too large to cross with farm equipment.

Stream erosion

Removal of soil from the banks and bed of permanent or intermittent streams.

Channel erosion

Erosion where water concentrates and flows in defined channels (rills, gullies, streams).

Geologic erosion

Natural background soil loss occurring at about the same rate as soil formation (~1 mm yr⁻¹).

Accelerated erosion

Human-induced soil loss faster than formation, roughly 10 mm yr⁻¹.

Rainfall erosivity

Rain’s potential ability to cause erosion, governed by intensity and kinetic energy.

Slope steepness

Degree of inclination; steeper slopes increase runoff velocity and erosion risk.

Soil erodibility

Intrinsic susceptibility of soil to erosion, influenced by infiltration and structure.

Vegetative cover

Plants that intercept raindrops, slow runoff, and physically hold soil in place.

Universal Soil Loss Equation (USLE)

A = 0.224 R K L S C P; predicts average annual soil loss.

R factor

Rainfall erosivity index in the USLE.

K factor

Soil erodibility factor in the USLE.

L factor

Slope-length factor in the USLE.

S factor

Slope-gradient factor in the USLE.

C factor

Cropping-management factor; ratio of soil loss under a crop to that from bare soil.

P factor

Erosion-control practice factor; reflects effectiveness of contouring, strip-cropping, etc.

Tolerable soil loss (T)

Maximum erosion rate allowing sustainable, economical crop production.

Terracing

Engineering practice of constructing level benches across slopes to slow runoff.

Grassed waterway

Vegetated channel designed to safely convey excess runoff.

Check dam

Small barrier above a pond that slows runoff and traps sediment.

Pond (erosion control)

Depression below a check dam used to collect and store runoff.

Mulching

Covering soil with crop residues to reduce splash and maintain infiltration.

Cover cropping

Planting close-growing grasses or legumes to protect and improve soil.

Strip cropping

Alternate contour strips of erosive and protective crops (Pilas-tanim).

Crop rotation

Systematic sequence of different crops on the same land to balance nutrients and reduce pests.

Relay cropping

Second crop sown into a standing first crop near its harvest to use residual moisture.

Multiple cropping

Growing two or more crops per year (sequential or intercropped) to raise productivity and reduce erosion.

Alley cropping

Annual crops grown between hedgerows of pruned trees/shrubs supplying green manure.

High-density planting

Increasing plant population per unit area while managing competition.

Agroforestry

Integrated land-use system combining trees with agricultural crops or livestock.

Contour cultivation

Plowing and planting across slope lines to reduce runoff.

Minimum tillage

Seedbed preparation with minimal soil disturbance, leaving inter-row soil untilled.

Mulch tillage

Tillage leaving large amounts of crop residue on or near the surface.

Strip or zone tillage

Preparing only narrow strips for seed rows, leaving between-row soil undisturbed.

Subsoiling

Breaking hardpan below plow layer to increase infiltration and reduce runoff.

Ridge-tying

Connecting ridges with cross-ties to form water-holding basins.

Soil survey

Inventory describing, mapping, and interpreting soils of an area.

Map scale

Relationship of map distance to ground distance (e.g., 1 : 24 000).

First-order soil survey

Very detailed mapping; minimum delineation ≤ 1 ha (experimental plots, building sites).

Second-order soil survey

Detailed mapping for general agriculture or urban planning; 0.6–4 ha delineations.

Third-order soil survey

Extensive mapping for rangeland or community planning; 1.6–16 ha delineations.

Fourth-order soil survey

Reconnaissance mapping for broad land-use planning; 16–252 ha delineations.

Fifth-order soil survey

Exploratory mapping for regional/national planning; 252–4000 ha delineations.

Soil taxonomy

USDA system classifying soils by measurable properties related to genesis.

Diagnostic horizon

Distinct soil layer whose properties are used to classify soils.

Epipedon

Diagnostic surface horizon formed at or near the soil surface.

Mollic epipedon

Thick, dark, soft surface horizon with high base saturation (>50%).

Anthropic epipedon

Human-modified mollic-like surface rich in phosphorus (>250 ppm citric-soluble P₂O₅).

Umbric epipedon

Dark surface horizon similar to mollic but with low base saturation (<50%).

Histic epipedon

20–30 % organic matter surface horizon, saturated with water (organic soil).

Ochric epipedon

Thin, light-colored surface horizon that fails criteria for other epipedons.

Plaggen epipedon

≥ 50 cm thick man-made surface horizon formed by long-term manure additions.

Argillic horizon

Bt layer with illuvial accumulation of silicate clay.

Agric horizon

Subsurface layer enriched with clay and humus from long-term cultivation.

Natric horizon

Argillic horizon containing ≥ 15 % exchangeable sodium (Btn).

Spodic horizon

Illuvial accumulation of Fe/Al oxides and organic matter (Bs or Bhs).

Oxic horizon

Highly weathered layer rich in Fe/Al oxides and kaolinite, low fertility (Bo).

Sombric horizon

Light-colored, low–base saturation horizon in well-drained soils.

Placic horizon

Thin, dark, cemented pan of iron or iron-organic complexes.

Duripan

Subsoil horizon cemented by silica (SiO₂).

Fragipan

Dense, brittle subsoil layer hard when dry, firm when moist.

Albic horizon

Leached, light-colored subsurface from which clay and oxides were removed.

Calcic horizon

Subsoil accumulation of calcium carbonate.

Gypsic horizon

Layer enriched with gypsum (CaSO₄·2H₂O).

Petrocalcic horizon

Cemented calcic layer hardened by CaCO₃.

Cambic horizon

Weakly altered Bw layer showing initial color or structure development.

Soil temperature regime

Mean annual soil temperature category measured 50 cm deep.

Pergelic

Soil temperature regime with MAT < 0 °C.

Cryic

MAT 0–8 °C; cold soils with short warm season.

Frigid

MAT < 8 °C but warmer summers than cryic.

Mesic

MAT 8–15 °C.

Thermic

MAT 15–22 °C.

Hyperthermic

MAT > 22 °C.

Soil moisture regime

Classification based on presence of available water in the moisture control section.

Aquic

Saturated, reducing soil moisture regime lacking oxygen.

Aridic

Soil dry > 50 % of the time when temperature > 5 °C; moist < 3 months.

Torric

Very hot, dry Aridic regime of lower latitudes.

Ustic

Soil dry > 3 but < 7 cumulative months per year (seasonally dry).

Udic

Soil dry < 90 cumulative days; moisture usually adequate for plants.

Xeric

Dry, warm summers and moist, cool winters (Mediterranean climate).

Entisol

Very young soil with little to no horizon development (A/C profile).

Inceptisol

Young soil showing weak to moderate horizon development.

Aridisol

Soil of arid regions with limited weathering and often carbonate accumulations.

Gelisol

Soil containing permafrost within two meters of the surface.

Mollisol

Grassland soil with thick, dark, fertile mollic epipedon.

Andisol

Soil formed from volcanic ash; low bulk density, high P-fixing capacity.