SCSC-Module 1

Plant essential elements C.B. HOPKiNS CaFé Closed Monday Morning and Night CuZoon, the Mg

Remember that Al, Si, Na are common elements that are NOT essential for plants

Silicates

Primary: Quartz, feldspars, amphiboles, pyroxenes, horneblend, micas

Secondary: Kaolinite, smectite, vermiculite, chlorite

Other secondary minerals

Oxides (Fe and Al - NOT soluble and last products of weathering)

-Hematite, goethite, and gibbsite

Carbonates (somewhat soluble)

Calcite and dolomite

Sulfates (relatively soluble)

Gypsum

Halides ( very soluble)

Halite, Sylvite

Phosphate (very insoluble)

Apatite

Shapes

Spheroidal=granular & crumb

Blocky=angular&subangular blocky

Prism-like=columnar & prismatic

Platy=flat

Structureless=massive&single grain

Size

Very fine, fine, medium, coarse, very coarse

Grades

Strong, moderate, weak, structureless

Factors affecting aggregation

Cation type (Ca improves aggregation, Na does not)

Clay vs sand, which has the lower bulk density?

Clay (high micropore spare; sand has big, but few pores)

Macropores (>0.08mm)

Water drains out via gravity

Micropores (<0.08mm)

Small pores that are last to dry out because water is held tightly and slow conductor of water and air

Soil Color

Hue Value/Chroma

Hue=Color

Value=darkness to lightness (0-10)

4 or less=organic matter is likely to be present

Chroma=how much color (none to all, 0 to 10)

6 or more is likely to be red or organge

A soil that supports plant like must provide which of the following, EXCEPT

Nutrients, Oxygen, Water, carbon dioxide, and Physical support

The answer is Carbon dioxide

Primary minerals that may weather to form secondary clay minerals in soil include:

Feldspars, Hornblende, and Mica

Intensive weathering typically results in soil with high concentration of ________ because these are secondary mineral that are resistant to further weathering?

Hematite and gibbsite

Which of the following weathers to form silicate clay minerals in soil?

Hornblende and feldspar

Which of the following mineral is the most soluble? The high solubility causes it to easily weather and be lost from soil profiles?

Gypsum

The chemical composition of mineral in a residual soil usually has a ______ from that of the parent rock.

Lower percentage of basic cations (i.e., Ca, Na, Mg, K)

A soil typically contains a high percentage of ____ than the rock from which it is derived.

Al

Reactivity of material in soils is primarily a function of _____

Particle Size

The most probable sequence of soil textures surface to subsoil is

Sandy loam, clay loam, and clay

Surface soils are ____ than subsoil

More porous

Which physical soil property is an inherent property of the soil that cannot be changed in our lifetime?

Soil texture

Aggregation helps fine-textured soils become more suitable for plant growth because it ______

Increases macroporosity

Soil compaction has no effect on _______

Soil texture

A soil has a color of 10YR 4/1, the value is _____, which indicates that the soil is relatively dark in color

4