| A | B |
|---|
| physical properties of soils | texture, structure, internal drainage, compaction, color and shrink-swell ... |
| soil color determinants (2 primary) | (1) humus content, and (2) amount and chemical nature of iron compounds and certain elements/minerals |
| element | A substance that cannot be broken down by chemical means. Elements are defined by the number of protons they possess. |
| mineral | Usually inorganic substance which occurs naturally, and typically has a crystalline structure whose characteristics of hardness, lustre, colour, cleavage, fracture, and relative density can be used to identify it. Each mineral has a characteristic chemical composition. |
| rocks | composed of minerals |
| also a soil color determinant | how much and for how long the soil has been saturated with water |
| humus coloring | black or dark brown color |
| unweathered iron | has no color |
| oxidation of iron | exposed to oxygen, iron molecules combine with oxygen molecules to form iron oxides |
| bright red soils | high in iron content, well areated and well-drained |
| yellow soils | hydrated or moist soil conditions in the presence of oxygen |
| ferrous oxide | FeO = gray color |
| ferric oxide | hematite |
| hematite | Fe2O3 = red |
| hydrated ferric oxide | 2Fe2O3 + 3H2O = yellow |
| ferrous oxide | produced when the ferric iron soil has too much water and an absence of oxygen => gray color |
| reduced iron | oxygen is taken away from the iron & the iron can be "moved" from the soil by leaching; after the iron is gone the soil is gray |
| manganese color in soil | brown or black color; often seen in cracks in soil |
| mottled | several different colors intermixed |
| redoximorphic features | mottled coloring in the soil of gray along with red, yellow or brown soil colors |
| iron depletion in soil | produces a gray color |
| an accumulation of iron oxide (iron concentration) | produces a more red, yellow or brown color |
| gley soils | wetland soil coloring (super saturated for long durations) |
| soil texture | how the soil feels |
| three primary soil particles | sand, silt, and clay |
| largest soil particle - feels gritty | sand |
| medium-sized soil particle - feels silky like dry flour | silt |
| smallest soil particle - feels sticky when wet | clay |
| particles that give soil its plasticity2 | clay2 |
| sand particle size | 2mm - 0.5 mm |
| silt particle size | 0.5 mm - .002 mm |
| clay particle size | less than .002 mm |
