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soil study guide
APES
| Question | Answer |
|---|---|
| what is soil? | relatively thin surface layer of the Earth’s crust |
| What does soil consist of? | mineral and organic matter that is affected by agents such as weather, wind, water, and organism |
| What are the 4 distinct parts of soil? | mineral particles, organic matter, water, air |
| What percent of soil is mineral particles? | 45% |
| What percent of soil is organic matter? | 5% |
| What percent of soil is water? | 25% |
| What percent of soil is air? | 25% |
| Why is soil important to microorganisms? | inhabit the soil & depend on it for shelter, food & water |
| Why is soil important to plants? | Plants anchor themselves into the soil, and get their nutrients and water |
| Why is soil important to terrestrial plants | could not survive without soil, therefore, humans could not exist without soil either |
| Is soil a renewable or nonrenewable resource? | Renewable resource |
| What does soil provide nutrients for? | for plant growth and also helps purify water |
| What is weathering? | Soil formation begins when bedrock is broken down by physical, chemical and biological processes |
| What are mature soils? | soils that have developed over a long time |
| What are soil horizons | a series of horizontal layers |
| How is the parent material of soil formed? | The rock that has slowly broken down into smaller particles by biological, chemical, and physical weathering |
| How long does it take parent material to form? | To form 2.5 cm (1 in.) it may take from 200-1000 years |
| What are examples of physical weathering? | Erosion (wind, water, ice, etc) |
| List some examples of chemical weathering | A plant’s roots or animal cells undergo cell respiration and the CO2 produced diffuses into soil, reacts with H2O & forms carbonic acid (H2CO3). This eats parts of the rock away |
| What produces new soil? | decomposition |
| Where is soil NOT renewable | in tropical rainforests |
| Why isn't soil renewable in tropical rain forests? | all of the nutrients are caught in the trees and when cut down & burned the soil cannot get the nutrients back |
| How do you measure soil with texture | The percentages (by weight) of different sized particles of sand, silt and clay that it contains |
| What is the texture of gravel/stones | >2mm in diameter |
| What is the texture of sand | 0.05 to 2mm |
| Which has the larger soil particles? | Sand |
| What is the soil texture of silt? | .002 to .05 mm |
| What is about the size of flour and barely visible with the eye? | Silt |
| What is the soil texture of clay? | <.002mm |
| Which soil texture has the greatest surface value and can only be seen under an electronic microscope? | Clay |
| Why is gravel/stones not actually considered soil? | it doesn’t have direct value to plants |
| What does it mean if soil is gritty? | It has a lot of sand |
| What does it mean is soil is sticky? | high clay content and you should be able to roll it into a clump |
| What does it mean if soil is smooth, like flour? | It is silt |
| What is the structure of soil? | How soil particles are organized and clumped together. (Sand, silt, clay) |
| What is Friability in soil? | How easily the soil can be crumbled |
| What is the Porosity in soil? | A measure of the volume of soil and the average distances between the spaces |
| What is Permeability in soil | The rate at which water and air moves from upper to lower soil layers. It is distances between those spaces |
| How do soils vary? | in the size of the particles they contain, the amount of space between these particles, and how rapidly water flows through them |
| What is shrink well potential? | Some soils, like clays, swell when H2O gets in them, then they dry and crack. This is bad for house foundations, etc. |
| What is the pH of most soils? | 4.0 to 8.0 |
| What is the pH of the Pygmy Forest in California? | extremely acidic with 2.8 to 3.9 |
| What is the pH of Death Valley California? | very basic 10.5 |
| Why are plants affected by pH | because of the solubility of nutrient minerals |
| Why do steep slopes have little or no soil on them? | because of gravity |
| What does runoff from precipitation do to a slope? | it erodes it |
| What do moderate slopes and valleys encourage? | the formation of deep soils |
| Where are soils very shallow in texas? | San Antonio |
| Soil depth can range from? | 2 inches of soil then rock or 36 inches deep of soil |
| What does dark soil say? | it is rich with lots of organic matter |
| What does light soil like sand say? | not so rich with very little organic matter |
| What is the uppermost layer of the soil called? | O-horizon/Organic Layer |
| What is the O-horizon/Organic layer rich in? | organic material |
| What accumulates in the O-horizon? | plant litter and it gradually decays |
| When is the O-horizon completely absent? | in desert soils |
| When is the O-horizon a dominant layer? | in certain organically rich soils |
| What is horizon is top soil? | A-horizon |
| What is topsoil/A-horizon? | dark and rich in accumulated organic matter and humus |
| What horizon/layer has a granular texture? | Topsoil/A-horizon |
| Why is topsoil/A-horizon some what nutrient poor? | due to the loss of many nutrient minerals to deeper layers and by leaching |
| Which layer is the B horizon? | the sub soil layer |
| What is subsoil/B-horizon? | The light-colored subsoil beneath the A-horizon |
| Why is subsoil/B-horizon often a zone of illuviation? | nutrient minerals have leached out of the topsoil and litter accumulate |
| Which soil layer is typically rich in iron and aluminum compounds and clay? | Subsoil/ B-horizon |
| Which layer is the C-horizon? | Parent Material |
| What is in the C-horizon/Parent material? | contains weathered pieces of rock and borders the unweathered solid parent material |
| Why is C-horizon/Parent material often saturated with ground water? | Most roots do not go down this deep |
| What happens during Infiltration? | the downward movement of water through soil |
| What happens during Leaching? | dissolving of minerals and organic matter in upper layers carrying them to lower layers |
| What does soil type determine? | the degree of infiltration and leaching |
| What are macronutrients? | larger in atomic structure |
| What are examples of macronutrients? | Nitrogen, Phosphorus, Potassium |
| What are examples of micronutrients? | Selenium, Zinc, Iron |
| What are micronutrients? | smaller in atomic structure |
| What are organic fertilizers? | animal manure, crop residues, bone meal, and compost |
| What are inorganic fertilizers? | man-made from chemical compounds |
| What are benefits of inorganic fertilizers? | exact compositions are known; they are soluble & thus immediately available to the plant |
| What are the costs of inorganic fertilizers? | quickly leach away; this pollutes the water; doesn’t help the water holding capacity of the soil like organic fertilizers do |
| How much soil is eroded in the US each year? | 6.4 billion tons |
| How much would 6.4 billion tons fill up | this would fill 320 million average-sized dump trucks that, if parked end-to-end, would extend to the moon and ¾ of the way back |
| What is erosion | the movement of soil components, especially surface litter and topsoil, from one place to another |
| What do the roots of plants do in undisturbed ecosystems? | help anchor the soil |
| What destroys plant cover and leaves soil vulnerable to erosion? | farming, logging, construction, overgrazing by livestock, off-road vehicles, deliberate burning of vegetation |
| Destroying soil in a few decades ruins solid that took how long to produce? | what nature took hundreds to thousands of years to produce |
| Soil erosion lowers what? | soil fertility |
| Soil erosion can overload what? | nearby bodies of water eroded with sediment |
| What is sheet erosion? | surface water or wind peel off thin layers of soil |
| What is rill erosion? | fast flowing little rivulets of surface water make small channels |
| What is gully erosion? | fast-flowing water join together to cut wider and deeper ditches or gullies |
| Soil is eroding at what rate? | faster than it is forming on more than one-third of the world’s cropland |
| Soil erodes faster than it forms on most U.S. cropland, but since 1985 | it has decreased by 40% |
| What happened in the 1985 Food Security Act (Farm Act)? | farmers receive a subsidy for taking highly erodible land out of production and replanting it with soil saving plants for 10-15 years |
| What is splash (water erosion)? | water hits the soil at a severe angle (based on slope) which can erode soil |
| What is sheet (water erosion)? | when surface water moves down a slope or across a field in a wide flow and peels off fairly uniform sheets of soil. |
| What happens to topsoil during sheet erosion? | it disappears evenly, and may not be noticeable until too much damage has been done |
| What is mass slippage (water erosion)? | very wet and large amounts of soil slip away in large chunks called mud slides ex-California |
| What is Rill (water erosion)? | concentrated flow across the surface of soil. its leaves rivets called micro channels |
| Where does gully erosion happen? | on steep slopes where all or most vegetation has been removed. |
| What is saltation? | One particle hitting another and being blown across the surface of the soil |
| What is suspension? | airborne soil. ex- soil from lubbock is found in temple texas |
| What is surface creep? | mountains/sand dunes; surface creeping slowly across. Landslides are an example of a very fast surface creep |
| How much productivity of the worlds land has been lost due to degraded topsoil? | One third |
| What are the causes of desertification in degrading drylands? | Overgrazing, deforestation, erosion, salinization, soil compaction, natural climate change |
| What are the consequences of desertification in degrading drylands? | worsening drought, famine, economic losses, lower living standards, environmental refugees |
| Repeated irrigation can reduce crop yields by causing what? | salt buildup in the soil and water logging of crop plants |
| What happens during salinization? | irrigation water contains small amounts of dissolved salts, evaporation and transpiration leave salts behind, salt builds up in soil |
| What happens during water logging? | Precipitation and irrigation water percolate downward, the water table rises |
| What are ways to reduce soil salinization? | Reduce irrigation and switch to salt tolerant crops such as barley, cotton, and sugarbeet |
| What are ways to cleanup soil salinization? | Flush soil(expensive and wastes water), stop growing crop for 2-5 years, install underground drainage systems (expensive) |
| White alkaline salts have | displaced cops |
| What are shelter belts and what do they reduce? | can reduce wind erosion. Long rows of trees are planted to partially block the wind. |
| What can shelter belts help to do? | retain soil moisture, supply some wood for fuel, and provide habitats for birds |
| What is minimum tillage? | (conservation tillage) to disturb the soil as little as possible while planting crops |
| What happens during minimum tillage? | Special tillers break up and loosen the subsurface soil without turning over the topsoil, previous crop residues, and any cover vegetation |
| Fertilizers can help do what? | restore soil nutrients |
| What can runoff of inorganic fertilizers cause? | water pollution |
| What are hydrophonic crops? | crops grown in fertilized water |
| What soil is best for plant growth? | Loam |
| When does leaching occur? | when humus is dissolved and chemical compounds carried to lower layers |
| What is not a consequence of desertification? | abundant crop harvests |
Created by:
lasykes
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