SCSC 301 Exam 1 TAMU

Plants obtain from soil:

- Physical support

- Air

- Water

- Temperature regulation

- Protection

- Nutrient elements (17 essential elements)

Root respiration

- Produce CO2

- Release O2

(ventilation in soil pores)

Macronutrients (8)

- Calcium (Ca)

- Magnesium (Mg)

- Nitrogen (N)

- Potassium (K)

- Phosphorous (P)

- Carbon (C)

- Hydrogen (H)

- Oxygen (O)

- Sulfur (S)

Micronutrients (8)

- Copper (Cu)

- Iron (Fe)

- Manganese (Mn)

- Nickel (Ni)

- Zinc (Zn)

- Boron (B)

- Chlorine (Cl)

- Molybdenum (M)

Humus

organic component of soil

pedosphere

soil environment/interface

lithosphere

rock environment

regolith

a layer of unconsolidated debris overlying hard, unweathered rock

(ABC horizons; C horizons contain bulk rock material - above bedrock)

Sparolite

underlying rock has weathered in place to the degree that is loose enough to be dug

Soil Profile

a vertical section exposing a set of soil horizons

O Horizon

organic material layer at the soil surface

A Horizon

also called top soil, is the layer nearest the surface and is dominated by mineral particles and accumulated organic matter

Plow layer

formed by plowing and cultivating a soil to homogenize and modifies the upper 12 to 25 cm

E Horizon

usually just below the A horizon, intensely weathered and leached horizon that hasn't accumulated organic matter

B Horizon

also called subsoil;

- contain less organic material

- varying amounts of silicate clays, iron and aluminum oxides, gypsum, or calcium carbonate

- plant roots and microorganisms often extend below

C Horizon

are the least weathered part of the soil profile

Major components of a typical, moist soil

- 20-30% Air

- 20-30% Water

^pore space^

- 40-60% Minerals

- 1-5% Organic Matter

^Soil Solids^

% by volume

Three Mineral properties

- Sand (2-0.05mm)

- Silt (0.05-0.002mm)

- Clay (<0.002mm)

- Colloidal properties of clay (<0.001mm)

Soil Texture

12 soil textures

- Clay

- Sandy Clay

- Sandy Clay Loam

- Clay Loam

- Sand Loam

- Loamy Sand

- Sand

- Loam

- Silty Clay Loam

- Silty Clay

- Silt Loam

- Silt

Soil

Dynamic natural body having properties due to the combined effects of climate and biota as modified by relief acting on parent material over time.

5 things that affect soil

Active:

-climate

-biota

Passive:

-parent material

-time

Modifying:

-relief (topography)

Organic matter

- binds mineral particles into a granular soil structure that is responsible for loose, easily managed, productive soil

- increase the amount of water a soil can hold

- major source of P, S, N for plants

Humus

- black or brown in color

- a collection of very complex organic matter

- is the colloidal fraction of soil organic matter

- g for g, holds nutrients and

water < clay

- increase soil's capacity to promote plant growth

Soil gases

CO2 > O2

Diffusion

a measure of air movement due to differences in partial pressure of individual gases

Hydroscopic water

water which is held so tightly to silicate surfaces that it cannot move as a liquid

Typical structure description:

grade, size, type

hue

redness or yellowness

value

lightness or darkness

chroma

intensity of brightness