Soils Final - Other Sources

Soils differ from the parent material in many physical, ____________, and biological properties

Chemical

The term given to the layer of soil that is strongly affected by the roots of vegetation is ___________________

rhizosphere

What three particle types (from smallest to largest) are used to determine soil texture?

Clay

Silt

Sand

Give a reason that loam soil is generally considered best for plant growth?

provides a balanced and ideal environment for root development, water retention, and nutrient availability. This soil type is a combination of sand, silt, and clay, offering the perfect blend of these components to create a well-drained yet moisture-retaining medium. 

Between (1) Sand and (2) Clay, which has less total pore space?  Describe why this is the case.

Sand has less total pore space than clay.

This is because sand particles are larger, creating fewer, larger pore spaces (macropores).

Clay particles are much smaller, leading to a greater number of smaller pore spaces (micropores) overall, even though individual pores in clay are smaller, resulting in a larger total pore space. 

Soil bulk density is determined by the __________________ and _______________ of a soil.

Dry weight and Volume

What are the soil forming factors?

Climate

Topography

Vegetation

Parent Material Time

O Horizon definition

Primarily composed of organic matter, including decomposing plant and animal remains, and humus. It is the uppermost layer in the soil profile

A horizon definition

Also known as topsoil, this layer is a mixture of mineral particles and organic matter, often darker in color than the layers below. It is where most soil life resides. 

E horizon definition

characterized by the loss of clay, iron, aluminum, and organic matter due to leaching. It is often lighter in color than the A horizon and contains primarily sand and silt particles. 

B horizon definition

Also called subsoil, the B horizon is where leached materials, such as clay, iron oxides, and organic matter, accumulate. It is usually firmer and darker in color than the C horizon. 

C horizon definition

The parent material, the layer closest to bedrock. It is composed of rocks and materials that have been slightly weathered but still retain much of their original structure. 

(True/False) The three major soil parent materials in the coastal Pacific Northwest include Sedimentary, Ingneous, and Glacial Soils

True

In general, the effect of fertilization is to (a) increase, (b) decrease, (c ) leave unchanged; the pH level in soils

(b) Decrease

Neutral pH is __________________________?

7.0

Clay particles have a net ___________________ charge

negative

What is a reason that Cation Exchange Capacity (CEC) is an important property of soils?

It measures the soil's ability to hold and exchange positively charged nutrients, known as cations, which are essential for plant growth.

Atmospheric nitrogen must be fixed or changed to an available form for plants to use. Why is this necessary? Why can’t plants directly use the atmospheric nitrogen?

Plants cannot directly utilize it in its gaseous form (N2). The nitrogen gas in the atmosphere has a strong triple bond between its atoms, making it very stable and unreactive. Plants require nitrogen in a more reactive form, such as ammonia (NH3) or nitrate (NO3-), which they can absorb from the soil. 

Besides fertilization, what is one way that human activity has impacted the amount of nitrogen in the soils?

burning fossil fuels

industrial processes

What are ‘exodates’ and what function do they perform in soils?

fluids released by plant roots, containing various organic compounds. These exudates play a crucial role in plant-soil interactions, influencing nutrient acquisition, microbial communities, and overall soil health. 

Give a definition of humus.

dark, organic material that forms in soil when plant and animal matter decays

1)    What word is used to describe root fungus?

mycorrhiza

1)    Define soil erosion.

the wearing away and removal of topsoil by natural or human-induced processes, leading to the loss of fertile land.

1)    What is the difference between erosion and maSs wasting of soils?

Erosion is the physical removal and transportation of weathered material by water, wind, ice, or gravity. Mass wasting is the transfer or movement of rock or soil down slope primarily by gravity.

1)    What is the difference between soil porosity and soil permeability?

Soil porosity refers to the amount of void space (open space) within a soil, while permeability refers to the ability of water or other fluids to move through those spaces.

1)    Are bacteria more common in forest soils or agricultural soils?  Why?

Bacteria are generally more common and diverse in forest soils than in agricultural soils. This is primarily due to the natural organic matter, nutrient availability, and diverse habitats within forest ecosystems, which foster a greater abundance and diversity of bacterial communities. 

1)    What function do Nitrogen-Fixers perform?

Nitrogen-fixers, primarily bacteria and some cyanobacteria, convert atmospheric nitrogen gas (N2) into a usable form for plants, primarily ammonia (NH3). This process, called nitrogen fixation, is crucial for plant growth and overall ecological balance. 

Define Colluvium

1. material which accumulates at the foot of a steep slope.

Define Alluvium

material deposited by running water.

Define marine soils

soils that form in ocean environments

Define Lacustrine Soils

materials deposited in lake environments

Define Glacial Till

unsorted deposit of sediment created by a glacier, containing a mixture of materials

Define Glacial Lacustrine Soils

soils that formed in lakes fed by glacial meltwater

1)    What are the three main factors that determine a soils ‘Mineral Content’?

parent material

climate

time

1)    What is meant by the term ‘Cation Exchange Capacity’ and why is this important in soils?

a soil's ability to hold positively charged nutrients (cations) like calcium, magnesium, and potassium

important because these retained nutrients are then available for plant uptake, making CEC a key indicator of soil fertility and nutrient availability. 

1)    What is meant by the ‘Buffering Capacity’ of a soil and why is this important in soils?

The ability to resist changes in pH when acids or bases are added

1)    What is the ideal soil pH for most plants to take up most soil nutrients?

between 6.0 and 7.0.

1)    How do you increase a soils Buffering Capacity?

To increase a soil's buffering capacity, you primarily need to increase the amount of cation exchange capacity and reserve acidity. This is achieved through the addition of organic matter and/or liming. 

1)    What is a Cation?

a positively charged ion

1)    What is an Anion?

negatively charged ion

1)    What is diffusion and how does it assist in plants ability to uptake nutrients from the surrounding soil?

a natural process where particles move from an area of high concentration to an area of low concentration

1)    List three examples of Cation Nutrients that can be found in the soil

calcium

magnesium

potassium (K+)

1)    Describe the Soil Food Web and why it is an important process in soil development

The Soil Food Web is a complex network of interconnected organisms living in the soil, including bacteria, fungi, insects, and earthworms.

It's crucial for soil development as these organisms decompose organic matter, cycle nutrients, and improve soil structure

1)    What are soil microfauna and why are they crucial to healthy soil processes?

tiny animals, often microscopic, that inhabit the soil and play a vital role in soil health.

They are crucial for processes like decomposition, nutrient cycling, and soil structure maintenance. 

1)    What are soil macrofauna and why are thy crucial to healthy soil processes?

oil macrofauna are larger soil-dwelling organisms (like earthworms, ants, and termites) that significantly impact soil health and function.

They are crucial for healthy soil processes because they improve soil structure, facilitate nutrient cycling, and create favorable conditions for other soil organisms. 

1)    Why would a large population of soil macrofauna be a good indicator that you have a very healthy, nutrient-rich soil with lots of AVAILABLE soil nutrients?

these organisms play crucial roles in nutrient cycling, soil structure, and organic matter decomposition.

1)    What is denitrifying bacteria?  Where is it typically found?  Why is it an important process in the nitrogen cycle?  What is it doing to the nitrogen compounds it encounters?

Denitrifying bacteria are microorganisms that play a crucial role in the nitrogen cycle by converting nitrates into nitrogen gas.

They are commonly found in soil and water environments, particularly where oxygen levels are low. This process is important because it returns nitrogen to the atmosphere, completing a cycle that also includes nitrogen fixation, nitrification, and ammonification.

Denitrifying bacteria do this by utilizing nitrates as an electron acceptor in anaerobic conditions, ultimately producing nitrogen gas. 

1)    List two ‘high-energy’ natural events that can break N₂ bonds and make nitrogen available for plants in soils.

lightning and volcanic eruptions.

1)    Why is too much nitrogen in a soil bad?

Excess nitrogen can lead to excessive plant growth, reducing fruit and flower production. It can also cause problems with water quality, like eutrophication, and can impact human health.

1)    Describe the Nitrogen Cycle and all the processes involved

The nitrogen cycle is a biogeochemical process where nitrogen is converted into various forms, moving through the atmosphere, soil, and living organisms. It involves several key processes: nitrogen fixation, nitrification, denitrification, assimilation, and decomposition.