Soil Properties, Formation and Erosion

Question 1

Water holding capacity

Answer 1

the total amount of water soil can hold - varies with different soil types (refers to how much water soil holds on top of it - i.e. soils with high clay composition hold the most clay)

Question 2

Physical Properties of soil

Answer 2

• Permeability/infiltration
• Compaction
• Particle size/texture

Question 3

Chemical Properties of Soil

Answer 3

• pH
• Salinity
• Phosphate/Nitrogen/Calcium/Potassium content
• Cation exchange capacity (CEC) - ability of soil to adsorb & release cations
• Base saturation - proportion of soil bases to soil acids, expressed as a percentage

Question 4

How do the physical/biological properties of soil affect soil quality?

Answer 4

• Water inflitration abiliy
• Available oxygen
• Ability to be used for agriculture
• Ability to hold nutrients/moisture
• Organisms can be beneficial/harmful to agriculture crops

Question 5

How do chemical properties of soil affect soil quality?

Answer 5

• Different range of tolerances to pH and nutrient content (excess nutrients are harmful)
• Soils with higher pH can absorb more cations
• Plants need nutrients like nitrogen, phosphate, etc. to survive

Question 6

What is a biological property of soil?

Answer 6

-Presence of organisms/organic matter/leaf litter/humus/mulch/crop residue (fungi, bacteria, protozoans)

Question 7

Soil degradation

Answer 7

loss of some or all of a soil’s ability to support plant growth

Question 8

4 Ways that Humans Can Cause Soil Erosion

Answer 8

• Deforestation: The lack of roots holding down soil. They are often replaced with plants that worsen erosion, e.g., soybean, wheat
• Overgrazing: Pastureland can lead to cattle overeating & the top layer of soil can erode with wind & rain
• Pesticides & fertilizers: These can change the chemistry of the soil & kill microorganisms in soil
• Tillage practices (probably the biggest effect of erosion): turning & breaking up soil keeps top layer from accumulating organic material & roots –> we do this to add oxygen to the soil

Question 9

Sheet Erosion & Solution:

Answer 9

surface layer is removed by water

- maintain plant cover

Question 10

Rill erosion & Solution:

Answer 10

small channels of water flow
- strip cropping or *contour plowing (curving crops – creating a gentle slope to slow water runoff) or low or *no tillage (distributes the soil minimally, keeping it intact from wind & water erosion) practices

Question 11

Gully erosion & Solution:

Answer 11

wider cuts from expanded rill erosion

- divert water away from rills & gullies

Question 12

How does salinization occur and affect crops? What are possible solutions?

Answer 12

• Rain water would normally add fresh water, decreasing amount of salt in soil that was created from crops
• However, when employing irrigation tactics, which uses water from the ground, we are bringing up the salt with the water & reapplying it to the plants
• Crops cannot survive in high salt levels
  SOLUTIONS: flood out the ground with freshwater, use drip irrigation, change the types of crops to those with higher salt-tolerance

Question 13

What are the characteristics of sand, silt and clay (the material that makes up soil)?

Answer 13

Sand (large: 0.05 – 2.0 mm): with its large, loosely packed particles, drains quickly, high porosity, allows water to pass through
Silt (0.002 – 0.05 mm)
Clay (smallest <0.002 mm): drains much more slowly, doesn’t allow water to pass through (if so takes a very long time)

Question 14

How does soil compaction occur?

Answer 14

Driving on soil with heavy equipment (tilling) compacts the pores in soil needed, which will then destroy the soil and affect water inflitration and available oxygen

Question 15

How to Read a Soil Triangle:

Answer 15

Sand: slanted to left from bottom
Clay: horizontal
Silt: slanted to left from right side

Question 16

Physical weathering

Answer 16

mechanical breakdown of rocks & minerals

Question 17

Chemical weathering

Answer 17

breakdown of rocks & minerals by chemical reactions, the dissolving of chemical elements from rocks, or both.(biogeochemical cycles!)

Question 18

Biological weathering

Answer 18

organisms breaking down rock (remember succession & pioneer species!)

Question 19

Acid precipitation/Acid rain

Answer 19

Precipitation high in sulfuric acid & nitric acid from reactions between water vapor & sulfur & nitrogen oxides in the atmosphere

Question 20

What is Erosion? What are the two proccesses that lead to Erosion (natural and human)?

Answer 20

physical removal of rock fragments from a landscape or ecosystem

• Wind, water (runoff) & ice move materials downslope due to gravity (topography)
• Human factors – lead to water contamination – increased turbity in water

Question 21

What 5 factors influence the formation of soil?

Answer 21

Parent material: underlying rock material from which the inorganic components of a soil are derived
– rocks are broken down by wind & rain; soil tends to retain basic chemistry of this rock
Climate: average temperature & moisture change rate of weathering & leaching (nutrients in water), wind redistribution as well
Topography: slope of land may affect erosion
Biological factors: Organisms – plants, animals, microorganisms
Time: soil formation is a continous cycle

Question 22

O Horizon

Answer 22

The organic horizon at the surface of many soils, composed of organic detritus in various stages of decomposition. Humus is the most fully decomposed organic matter in the lowest section of this horizon. (most organic matter because this is where leaves fall & animals & plants die)

Question 23

A horizon

Answer 23

Frequently the top layer of soil, a zone of organic material & minerals that have been mixed together, also known as Topsoil (surface horizon – basic rock material with a lot of humus & organic material & minerals)

Question 24

E horizon

Answer 24

A zone of leaching, or eluviation, found in some acidic soils under the O horizon or, less often, the A horizon. Pulls minerals out & then leaves a dry layer (not in all soil types)

Question 25

B horizon

Answer 25

A soil horizon composed primarily of mineral material with very little organic matter. (subsoil – minerals & nutrients, not a lot of organic material)

Question 26

C horizon

Answer 26

The least-weathered soil horizon, which always occurs beneath the B horizon & is similar to the parent material. (substrata – most parent material)

Question 27

R horizon

Answer 27

Bedrock – base layer that changes the properties above it , sits below the soil horizons