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EESC456-CHAPTER1 Flashcards

1
Q

Uses of soil science

A
  1. agricultural planning (site potential)
  2. productivity (plant nutrition, chemical cycling, mgmt soil fertility+productivity for nutrient supply)
  3. Prevent soil loss (erosion, degradation)
  4. Engineering uses + limitations
  5. Site restoration (of productivity), ecology, enviro aspects (revegetation of disturbed/mined sites)
  6. forensics
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2
Q

5 functions of soils = important ecosystem services (provisionning, regulating, supportive, cultural)

A
  1. Medium for plant growth (determining nature of vegetation/animals)
  2. Hydrological role of soils (regulate water supplies and purification)
  3. Recycler of raw materials (nutrients/organic wastes)
  4. Influences composition and physical conditions of atmosphere (gas exchanges)
  5. Habitat for soil organisms
  6. Engineering medium (building materials for earth + humans); most constructed structures rest on soil, require soil excavation or soil-made materials for building.

soils = needed to sustain life on earth

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3
Q
  1. Growth medium for plants
A
  • Physical support (root system)
  • Water supply (water-holding capacity)
  • Air supply: respiration of roots using O2 producing CO2
    –>Ventilation: maintain quality + quantity of air by allowing CO2 escape, O2 to enter root zone via networks of soil pores.
  • Temperature moderation (soil insulating properties protecting root system from extremes at soil surfaces)
  • Protection from toxins by ventilating gases (by decomposing/adsorbing organic toxins or surprising toxin-producing organisms)
  • Supply of dissolved mineral nutrients (18 essential elements; nitrogen converted by bacterias into organic N compound)
    –> animals eat plant
    –>roots take elements out of soil solution, plants incorporate into organic compounds in its tissues
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4
Q

Plant nutrition - 18/92 naturally occuring elements for plant growth/health

A

C.B.HOPKiNS Café Co. Closed Monday Morning and Night
See You Zoon, the Mg

Carbon, boron, hydrogen, oxygen, phosphorus, potassium, nitrogen, sulfur, calcium, iron, cobalt, chloride, manganese, nickel, zinc, magnesium, copper, molybdenum

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5
Q

What is soil

A

Interface (overlap) between 4 spheres.

The unconsolidated mineral or organic material on the immediate surface of the Earth that serves as a natural medium for plant growth.

Unconsolidated layer (materials on surface of earth): Regolith, saprolite

Regolith: unconsolidated layer of debris underlying hard, unweathered rock. Varies in thickness. Rock exposed at Earth’s surface crumbled/decayed to produce this layer.
–> regolith materials can be transported from initial formation site, then deposited over bedrock.
–> regolith material may or may not be related to rock now found below it.

Saprolite: where underlying rock has weathered in place to some degree that it is loose enough to be dug.

Natural substance and a living medium

Soil as a material (minerals, gases, water, organic substances, micro-organisms)
–> A soil = 3D natural body
–>The soil = collection of individually different soil bodies, covering land.

Soils as natural bodies composed of soil material, roots, animals, rocks, artifacts, etc.

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6
Q

4 spheres = pedosphere (soil)+ different scales

A
  1. Atmosphere (soil air: gases CO2, O2, N)
  2. Biosphere (organic matter + biomass: plants, animals, microbes, products)
  3. Hydrosphere (soil water, dissolved substances)
  4. Lithosphere (soil particles: mineral in rocks, clays, sediments)

–> Global
–>Landscape
–>macro/microscopic
–>submicroscopic

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7
Q

Soil forming processes work (mostly
vertically) to create …

A

horizons

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8
Q

describe horizons

A

Characteristic soil profile. Soils develop horizons – history of a
site; develop into a recognizable
“bodies”

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9
Q

Describe horizon process

A
  • Addition of organic matter from above
  • Solutes & suspended solids leached
    downwards through profile
  • Breakdown products move downwards
    – clays, oxides, secondary minerals,
    carbonates, humus

–> O, A, E, B (subsoil), C (parent materials soil is forming in)

–>grass NOT a horizon, it is just organic matter/litter

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10
Q

Transitions between horizons are…

A

rarely distinct

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11
Q

Soil composition by volume

A

1/2 Pore space:
Air = 20-30%
Water = 20-30%

1/2Soil solids:
Organic = 2-5%
Mineral = 45%

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12
Q

The solid mineral component = 3 size classes

A

Sand particles: round 2-0.05 mm
Silt particles: round 0.05-0.002 mm (floury, talcum powder size)
Clay: platey <0.002mm (sticky when wet, lumpy when dry)
Colloidal clays: <0.001mm (so small they stay suspended in soil solution)

Ignore over 2mm diameter (gravel, stones, rocks); too inert to be active in soil, maybe important in physical properties

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13
Q

different clay minerals have..

A

different properties

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14
Q

Define Texture

A

Proportions (mix) of particles of different sizes in soil.

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15
Q

Source of organic matter in soils

A

plants, animals, micro-organisms (from outside + within soil body)

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16
Q

Organic matter is ….; decomposes and needs continual ….

A

dynamic
replenishment

soil = dynamic entity, always changing and always changed by its external environment

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17
Q

Functions of organic matter (6)

A
  1. structural role: binding agent in soil matrix (clays), aggregation soil particles
  2. Nutrient supply (clays)
  3. Source of energy to soil biota (from decomposition of organic matter)
  4. Enormous water-holding capacity
  5. Crucial in determining Humus = important component of soil colloids
  6. Carbon sink, stores carbon in soil as organic matter (balance CO2, reducing atmospheric CO2 concentration; mitigation climate change)
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18
Q

pH (acidity or alkalinity) affects…

A

biological + chemical activity

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19
Q

Soil solution is a soup of

A

dissolved + colloidal material/nutrients (suspended solids) + micro-organisms

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20
Q

Changing role of soil water

A

–> varies in amount in soils (seasonnally)

–> held with increasing energy/tension as soil dries; soil solids attract remaining water; plants having to overcome tension to access it

–> vital for life (where microbes live)

–>soil processes can remove impurities, kill potential disease organisms to purify/cleanse contamineted water soaking through upper layers.

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21
Q

Small pores are more likely to fill with….Large pores are more likely to fill with… first

A

water
air

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22
Q

Role of soil air

A

Occupies pores in soil matrix
–>Vital oxygen supply for soil ecosystem (only some organisms can live without air)

–>balance of gases different from atmosphere. overtime quality of soil and air differs due to the differences from transformations (respiration)

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23
Q

In soil (compared to atmosphere), CO2 is…. and O2 is …

A

higher; due to poor exchange with atmosphere

lower; respiration by s-s biomass (microbes consume O2 and produce CO2)

24
Q

Interactions of 4 components (water, air, minerals, organic matter) that form soil characteristics

A

All interact upon each other (not independent)
Most interactions = in nutrient supply
Organic matter affects porosity+ water-holding capacity which affects air/water supplies which affects habitat

25
Q

How is nutrient availability linked to cash liquidity

A

A. structural framework of primary minerals + organic matter: slowly available = long-term investments–>highest amount, most restricted availability

B. colloidal fraction (structural framework of clay/humus): slowly available = short-term investments

C. adsorbed fraction (ions held on colloidal surfaces): moderately available = checking account

D. soil solution fraction (ions freely available for plant roots absorption) = pocket cash–>less amount, but highest availability.

26
Q

Arid climates = higher levels of… + … is less abundant (linked to organic matter)

A

soluble elements
Nitrogen

27
Q

Soil = renewable or reusable resource?

A

Depends of timescale:

Reusable: short-time scale (human societies)
–> soil forming not fast enough if we degrade it. must care for it adequately if want to preserve productivity.

Renewable: conceptually yes as soil is forming continually from a geological timeframe.

Soil supply = finite

–>renewable resources derived from soil to replace non-renewable resources

28
Q

Soils evolve as unique individuals reflecting their…

A

developmental environments

29
Q

Soil husbandry is an … practice

A

ancient
Nile valley in Egypt to Mesopotamia (Persia)

30
Q

Higher organic matter = … water-holding capacity

A

Higher (so higher water release for plants)

31
Q

Soil colloids

A

Humus + fraction of clay particles

32
Q

Humus:

A

break down product of organic matter. stable end-product of decomposition of organic matter

33
Q

3 main carbon sinks in Canada

A
  1. wetlands
  2. peatlands
  3. permafrost
34
Q

Greater porosity (larger pores +… + …

A

greater habitat

higher exchanges with atmosphere = difference between air soil/atmosphere will be lower

35
Q

pH of soil = pH of soil…

A

solution

= master variable, influences many aspects of soil

36
Q

Soil degradation: (4)

A
  1. Erosion (topsoil, surface); leaving bare soils for too long = wind, water…
  2. salinization (incorrect irrigation mgmt); water evaporates and salts concentrate on roots, build up of soil no longer producing.
  3. depletion of organic matter/nutrients; soil overuse, organic matter lower so it can no longer maintain soil productivity
  4. Contamination with toxic substances; localized or general sites (irrigation with contaminated water, air pollution from industrial activities, acid rains)

–> bad agricultural practices = soil loss rates&raquo_space;» soil forming rates

37
Q

The nature and management of soils in a watershed will influence …. +….finding its way to aquatic systems.

A

the purity + amount of water

38
Q

…. is a major source of water vapour in the atmosphere, altering temperature, composition and weather patterns

A

Evaporation of soil moisture

39
Q

Critical zone

A

The outer layers of the Earth that lie between the tops of tallest trees and bottom of groundwater aquifers feeding rivers.

40
Q

The soil is part of the… and A + B horizons are part of the … C horizon is part of the … that underlies the solum (may be slowly changing into soil)

A

regolith

solum (Latin meaning soil or land)

regolith

–>regolith can be so thin that it has been changed entirely to soil so solum rests directly on the bedrock

41
Q

Living organisms (bacterias, fungi, plant roots) have altered the upper part- or entire depth- of the regolith through their….

A

biochemical and physical effects

42
Q

Soil is the product of both destructive and creative (synthetic) processes.

A

Destructive;
a. weathering of rock
b. microbial decay of organic residues

Synthetic;= formation of contrasting layers = soil horizons.

a. formation of new minerals
b. formation of new organic-mineral complexes

43
Q

Development of soil horizons in the… is a unique characteristic of soil that sets it apart from the…

A

upper regolith

deeper regolith materials

44
Q

The most important interactive process involving the four soil components is the ….

By a series of chemical and biochemical processes, …to replenish those in the soil solution. For example, the tiniest colloidal-sized particles—both clay and humus—exhibit negative and positive charges. These charges tend to …. and hold them as exchange-able ions.

A

provision of essential nutrient elements to plants.

–>Plants absorb essential nutrients, along with water, directly from one of these components: the soil solution. However, the amount of essential nutrients in the soil solution at any one time is sufficient to supply the needs of growing vegetation for only a few hours or days. Consequently, the soil solution nutrient levels must be constantly replenished from the inorganic or organic parts of the soil and from fertilizers or manures added to agricultural soils.

nutrients are released from these solid forms

attract or adsorb oppositely charged ions from the soil solution

45
Q

Some scientists consider that the … is among the most important of chemical reactions in nature. Through ion exchange, elements are released from this state of … on colloidal surfaces and escape into the …where they can be readily taken up (absorbed) by plant roots. Nutrient ions are also released to the soil solution as …. decompose organic tissues. Plant roots can readily absorb all of these nutrients from the soil solution, provided there is enough O2 in the soil air to support root metabolism.

A

ion exchange process
electrostatic adsorption
soil solution
soil microorganisms

46
Q

Most soils contain large amounts of …relative to the annual needs of growing vegetation. However, the bulk of most nutrient elements is held in the … + …… Only a small fraction of the nutrient content of a soil is present in forms that are readily available to plants. Table 1.3 will give you some idea of the quantities of various essential elements present in different forms in typical soils of humid and arid regions.

A

plant nutrients

structural framework of primary and secondary minerals and organic matter

47
Q

Plant roots do not ingest soil particles, no matter how fine, but are able to …. Because elements in the coarser soil framework of the soil are only slowly re- leased into the soil solution over long periods of time, the bulk of most nutrients in a soil is ….

Nutrient elements in the framework of colloid particles are somewhat more readily available to plants, as these particles break down much faster because of their greater surface area. Thus, the …is the major storehouse and, to some extent, a significant source of … in many soils.

A

absorb only nutrients that are dissolved in the soil solution.

not readily available for plant use.

structural framework

essential elements

48
Q

The bulk of the nutrients is locked up in the …. of (4)…
A smaller proportion of each nutrient is adsorbed in a swarm of ions near the surfaces of ….. From the swarm of adsorbed ions, a still smaller amount is released into the bulk
soil solution, where uptake by plant roots can take place. Luckily, in a fertile soil, the process described can help re- plenish the soil solution as quickly as plant roots remove essential elements. Maintaining the supply of available nutrients at the …is thus a process that involves complex interactions among different soil components.

A

structural framework

primary minerals, organic matter, clay, and humus.

soil colloids (clay and organic matter)

plant root surface

49
Q

3 principal mechanisms by which nutrient ions dissolved in the soil solution come into contact with plant roots/by which the concentration of nutrient ions at the root surface is maintained

All three mechanisms may operate simultaneously, but one mechanism or another may be most important for a particular nutrient.

A
  1. root interception; roots continually grow into new, undepleted soil. Root exploration in search of nutrients is much enhanced by thin root cell extensions called root hairs.
  2. Mass flow; when dissolved nutrients are carried along with the flowing soil water toward a root that is actively drawing water from the soil. In this type of movement, the nutrient ions are somewhat analogous to leaves floating down a stream. Even with root hairs extending into tiny water-filled soil pores where nutrients may be dissolved, for the most part, nutrient ions must still travel some distance in the soil solution to reach the root surface.
  3. Diffusion; Nutrient ions continually move by diffusion from areas of greater con- centration toward the nutrient-depleted areas of lower concentration around the root surface. This way, plants can continue to take up nutrients even at night, when little, if any, water is absorbed into the roots.
50
Q

In the diffusion process, the random movements of ions in all directions cause a net movement from areas of .. to…., independent of any mass flow of the water in which the ions are dissolved.

Factors such as … (3), which reduce root interception, mass flow, or diffusion, can result in poor nutrient uptake by plants even in soils with adequate supplies of soluble nutrients.

Furthermore, the availability of nutrients for uptake can also be negatively or positively influenced by the … that thrive in the immediate vicinity of roots.

A

high concentration to areas of lower concentrations

soil compaction, cold temperatures, and low soil moisture content

activities of microorganisms

51
Q

To be taken up by a plant, the nutrient element must be in a … and must be located… Often, parts of a root are in such intimate contact with soil particles that a direct exchange may take place between … and…

A

soluble form and must be located at the root surface.

nutrient ions adsorbed on the surface of soil colloids and H+ ions from the surface of root cell walls.

52
Q

The plant membrane separating the inside of the root cell from the soil solution is … to dissolved ions only under special circumstances.

Plants do not merely take up, by mass flow, those nutrients that happen to be in the water that roots are removing from the soil. Nor do dissolved nutrient ions brought to the root’s outer surface by mass flow or diffusion cross the root cell membrane and enter the root passively by diffusion.

A

permeable

53
Q

A nutrient is normally taken up into the plant root cell only by …. embedded in the root membrane. These proteins form hydrophilic channels across a (otherwise hydrophobic lipid (fatty)) membrane. Energy from metabolism in the root cell is used to activate this carrier protein so that it will pass the nutrient ion across the cell membrane and release it into the cell interior.

This carrier mechanism allows the plant to accumulate … inside the root cell that far exceed …

Because different nutri- ents are taken up by specific types of protein molecules, the plant is able to exert some control over …

A

reacting with specific chemical binding sites on large protein molecules

concentrations of a nutrient

that nutrient’s concentration in the soil solution.

how much and in what relative proportions essential elements are taken up.

54
Q

Nutrient uptake being an …process, conditions that inhibit root metabolism may also inhibit nutrient uptake.

Examples of such conditions include …(2) resulting in …(3) that result in low translocation of sugars to plant roots.

A

active metabolic

excessive soil water content
soil compaction

poor soil aeration
excessively hot or cold soil temperatures
aboveground conditions that result in low translocation of sugars to plant roots.

55
Q

Plant nutrition involves (3)…processes and interactions among many different components of soils and the environment.

A

biological, physical, and chemical

EESC456 (11 decks)

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