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SOILS Exam 2
| Question | Answer |
|---|---|
| Ultisols are in what kinds of regions? | Warm, humid |
| Alfisols are in what kinds of regions? | Cool, humid |
| Ustolls are in what kinds of regions? | Semiarid |
| Natragids (aridisols with natic horizons (think exchangable sodium)) are in what kinds of regions? | Arid |
| What property of a water molecule has the most significant influence on the forces of adhesion and cohesion and consequentially influences many other soil properties? | The atom orientation and bond angle |
| What are the four major types of colloids in soils? | Layer silicate clays, Fe and Al oxides, amorphous clay/allophane and humus |
| Water flows through the soil by three types of movement identify them. | Saturated, unsaturated and vapor |
| What is isomorphic substitution? | when one element fills a position usually filled bt another of similar size |
| Which soil colloid would you use to make a vase from (and the glossiness on our lab manuals)? | Kaolinite |
| Which soil colloid would you use to seal a well? | Montomorillonite (smectite) |
| Which soil orders would be expected to have the greatest amount of montmorillonite clay? | Vertisols and mollisols |
| Which soil order would be expected to have the greatest cation exchange capacity? | Entisols, newer soils have higher charges. |
| What happens in the soil at a site where the timber is harvested and hauled from the mountain? | The density of the soil increases - fewer macropores. |
| What is the estimated bulk density of cultivated soil is what? | 1.3g/cm3 or 1.3Mg/m3 |
| What is the assumed particle density of soil? What would make it higher? Lower? | 2.65g/cm3, but would be closer to 3g/cm3 if it contains dense materials like garnet or hornblende, and as lower if it contains SOM which has a particle density of around 1g/cm3 |
| Which soil texture would have the greatest cation exchange capacity? | Clay loam |
| What are three facts about CEC in soils? | It varies with each soil depending on the soil pH, it will affect the buffer capacity of a soil and it varies with each soil depending on the number of exchangeable base cations |
| Which soil colloid has the greatest amount of cation exchange capacity? | Humus, very acidic, lots of hydrogen |
| Increasing soil pH will result in an increase in cation exchange capacity, why? | The higher (more basic) the soil, the more available sites and charges |
| Oklahoma native prarie has highest _____, but it is still only what % of the soil? | SOM, but only 3-4% |
| What is the Lyotropic series? | What basic cations are most likely to attach themselves in a CE. --> Al3+>H+>Ca2+>Mg2+>K+= NH+4>Na+ |
| How to calculate the CEC? | Number of cites/weight of colloid (cmolc/kg) |
| What are the two primary causes of negative charge in soils? | isomorphic substitution and dissociation reactions at the edge of the colloid (H+) |
| What are two examples of colloids which source of charge come from isomorphic substitution? | Illite and montmorillonite |
| List of soils and soil materials from lowest to highest CEC... | Kaolinite, Fe&Al oxides, loamy sands, sandy loams, silt loams, fine-grained micas and chlorites, clay loams, finished compost, vertisols, smectitles, histosols, vermiculites, humus |
| Typical CEC cmolc/kg for sand? Sandy loam? Loam? Silt loam? Clay and clay loam? | Sand - 2-3cmolc,kg -- sandy loam - 3-10cmolc,kg -- loam 11-16cmolc/kg -- silt loam - 13-26cmolc/kg --clay/clay loam -- 4-58cmolc/kg |
| 1:1 type silicate clays | kaolinite, 1 tetrahedral sheet and 1 octahedral sheet |
| 2:1 type silicate clays | smectite (montmorillonite), vermiculite - 1 octahedral sheet between 2 tetrahedral sheets |
| Nonexpanding 2:1 silicate minerals | micas and chlorites |
| What soil order has the lowest CEC? the highest? | Ultisols. Histosols. |
| Give an example of an inorganic colloid and an organic colloid. | inorganic: SiO2 organic C10H8 |
| What is the size of a colloid? | <2 micrometers in diameter, means big SA (10^-6m) |
| Kaolinite info | 1:1 clay mineral, layers held together by H-bonding, has a fixed structure, no expansion, little isomorphic substitution, terra cotta pots, shiny on lab manuals, and it's SA is 10-30m^2/g |
| Illite info | 2:1 clay mineral, non-expanding, can clean up wells, potassium between sheets binds them together, isomorphic charge in tetrahedral sheets, K+, Fe2_, Zn2+, Mg2+ in octahedral,and its SA is 70-100m^2/g |
| Smectite (montomorillonite) info | 2:1 clay, found in vertisols and mollisols, expanding, lots of shrink-swell, seal well up, H2O, K+, Ca2+ between sheets, weak bonds, isomorphic substitution in octahedral sheet (Mg2+ for Al3+) very cohesive,SA is 700-800m^2/g so good at storing H2O... |
| What are the 12 soil orders from youngest to oldest? | Entisols, Andisols, Histols, Gelisols, Inceptisols, Aridisols, Vertisols, Alfisols, Mollisols, Ultisols, Spodisols, Oxisols |
| Vermiculite info | 2:1 clay mineral, used as insulation, limited expansion, K+ and Ca2+ binds between sheets, isomorphic substitution in tetrahedral sheet (Al3+ for Si4+), SA 50-100m^2/g |
| Fe and Al oxides are in what soils? | highly weathered soils like ultisols and oxisols |
| What is an example of an Fe or Al oxide? | Gibbsite Al2O3+H2O |
| Fe and Al oxide info | little isomorphic substitution, charge is not constant, depends on pH |
| Amorphous minerals/allophane info | poor crystal structure, lots of + and - charges, allophane = Al2O3+2SiO2H2O from volcanic ash |
| Humus info | not crystal, H C O, charge changes with pH |
| Improve aggregation | add organic matter, add soil conditioners, alter cations |
| Principles for managing soil structure for Plant Growth | minimize tillage passes, restrict tillage timing, restrict traffic, maintain surface residue |
| Management Affects on Pore Space | improve aggregation, promote physical contact (wet/dry,freeze/thaw, plant roots) |
| Principles for managing soil structure for plant growth | cover crops, sod crops, practices which protect the soil from plant also improve plant growth |
| Principles for managing soil structure for engineering is opposite than for plant growth | decrease aggregation, want stable base, little compressibility |
| Rocks are composed of what? | 2 or more minerals and can be placed into categories of igneous, sedimentary and metamorphic |
| Minerals are defined as what? | a naturally occurring homogeneous solid with a definite, but not generally fixed chemical composition and an ordered atomic arrangment |
| Big crystals make what kind of soil? | Coarse soil, like sand |
| When it comes to rocks, what is physical weathering? | getting beat up, glaciers, dominates where there isn't much rain |
| When it comes to rocks, what is chemical weathering? | Almost always involves water, redox reactions, chemically different |
| A soil profile with sand, low SOM and cultivation would have higher or lower bulk density? | Higher |
| What soil colloid would be commonly found in soil series of the soil order Andisol? | Allophane as it's made from volcanic ash |
| Using polyacrylamide as a binding agent for soil aggregates will? | increase the percentage of macropores thus decreasing runoff from precipitation |
| Bulk density increases with soil depth because of what? | there is less organic matter, fewer aggregates, fewer roots and organisms and there is compaction from upper layers. |
| What is the ionic double layer? | The distributin of cations i nthe soil solution resulting from the simulatneous attraction toward colloid particles by the particle's negative charge and the tendency of diffusion and thermal forces to move the cations away from the colloid surface. |
| Soil Management decisions fall into what 3 basic categories? | Transport (increase or decrease in water flow), pore space (increase or decrease compaction), molecule storage (nutrients, fertilizer, contaminates) |
| How does soil affect the hydrological cycle | It acts as a natural filter and a chemical reactor |
| What are the five soil uses? | Medium for plant growth, affects the hydrological cycle, habitat for living organisms, support material for infrastructure and natures recycling center |
| What is the definition of soil? | Soil is a dynamic natural body composed of minerals, organic materials, air and water which acts and is acted on by living organisms in a thin layer covering the earth's surface |
| Soil is composed of what 4 spheres? | hydro (25%), litho (45%) bio (5%) atmo (25%) |
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